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Article Cite This: ACS Omega 2018, 3, 10058−10065
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Modulation of Hydrogen Evolution Catalytic Activity of Basal Plane in Monolayer Platinum and Palladium Dichalcogenides Haihua Huang,† Xiaofeng Fan,*,† David J. Singh,§ and Weitao Zheng†,‡ †
Key Laboratory of Automobile Materials, Ministry of Education, and College of Materials Science and Engineering and ‡State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130012, China § Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211-7010, United States
ACS Omega 2018.3:10058-10065. Downloaded from pubs.acs.org by 185.252.218.101 on 08/30/18. For personal use only.
S Supporting Information *
ABSTRACT: With an appropriate catalyst, hydrogen evolution reaction (HER) by water splitting can be used to produce hydrogen gas. Recently, layered transition-metal dichalcogenides have been proposed as alternative HER catalysts. However, a significant challenge is how to obtain the highdensity active sites. With first-principle calculations, we explore the possibility of defect engineering to trigger the HER catalytic activity of basal plane by analyzing monolayer PdSe2, PtSe2, PdTe2, and PtTe2. It is found that the doublevacancy DVSe (DVTe) and B-doping can modulate appropriately the interaction between H and basal plane and improve the HER activity of these transition-metal dichalcogenides. Especially, the B-doping with high concentration can increase enormously the density of active sites on basal plane. nanoparticles,11 and nanowires,33 has been the typical method at present. Because of the thermodynamic stability of basal plane and the dominant exposed surface of monolayer TMDs, another strategy is to activate the basal plane of TMDs through defect engineering and/or phase engineering.34−39 For example, with 1T′ phase, MoS2 exhibits metallic characteristic. Phase transition from 2H to 1T′ has been investigated as a method of tuning electronic properties to improve the HER activity. Defect engineering is also expected to activate the inert basal plane. It have been found that introducing the S vacancies and strain could activate the basal plane of monolayer 2H-MoS2 for HER.40 The doping with transition metal and light element has been proposed to improve the catalytic activity of inert basal plane.41−44 In fact, various structural defects, such as point defects and grain boundaries, have been observed in twodimensional (2D) materials, and were proposed to bring additional active sites for monolayer TMDs to improve the HER ratio.35 Recently, platinum- and palladium-based dichalcogenides were synthesized and proposed to be as the catalysts for HER.45 In this work, we explored the way of defect engineering to activate the basal plane of PdSe2, PtSe2, PdTe2, and PtTe2 for HER by first-principle calculations combined with the basic theory about HER. We mainly investigated the HER activity of basal plane by introducing different kinds of vacancies and the Bdoping in monolayer. First, we analyzed the formation of different vacancies and the possibility of B-doping. Then, we
1. INTRODUCTION Hydrogen as an energy carrier can be used to produce clean electricity in hydrogen fuel cells.1 Among different hydrogen production methods, electrolytic water as a sustainable one has been concerned.2−5 The hydrogen evolution reaction (HER), as the cathodic half-reaction of water splitting, is vital for the production of hydrogen gas. In acidic condition, the total HER includes two processes.6 The first step is hydrogen adsorption onto a catalyst by Volmer reaction with H+ + e− → H*, where the prefix of * represents the adsorption site of the catalyst. The second step is releasing of molecular hydrogen through two different mechanisms, Heyrovsky reaction H* + H+ + e− → H2+* and Tafel reaction 2H* → H2 + 2*. To decrease the overpotential and thus accelerate the reaction rate, searching for high-efficiency electric catalysts to reduce the reaction barrier becomes important in this filed. Platinum is the most electrochemically stable catalyst and exerts excellent HER electrocatalytic performance.7−9 However, the high cost and earth-scarcity have hindered its widespread use. It is urgent to find new efficient and abundant electrocatalyst for HER. The two-dimensional materials, such as layered transition metal dichalcogenides (TMDs), have been reported to exhibit superior catalytic properties for the electrocatalytic applications and emerged as alternative to Pt.10−25 As a prototype, MoS2 with different phase structures (such as 1T′ and 2H) has been widely studied.26−29 It has been found that the basal plane of MoS2 is catalytically inert and the catalytic activity originates from the sulfur-terminated Mo-edge and S-edge state for 2H phase.29−31 To enhance the catalytic performance of MoS2 catalysts, it is considered critical to be make a substantial fraction of exposed edge sites. Synthesizing the nanostructures, such as nanoflakes,32 © 2018 American Chemical Society
Received: June 22, 2018 Accepted: August 3, 2018 Published: August 29, 2018 10058
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experimental values.45 The bond length of Pt−Se is similar to that of Pd−Se, and the bond length of Pt−Te is similar to that of Pd−Te. All the four monolayers are semiconductors. To analyze the defect effect, we considered four kinds of defect structures, including single-vacancy of metal atom (VPd and VPt), single-vacancy of nonmetallic atom (VSe and VTe), double vacancy (DVSe and DVTe), and the B-doping (BSe and BTe). Here, we chose boron as the doping element mainly due to the obvious difference of electronegativity between B and Se (Te). It is expected that the B-doping can introduce the band gap states to active the basal plane. With PtSe2 as an example, these defect models are shown in Figure 1. These defect models are constructed in a 4 × 4 supercell. To assess the thermodynamic stability of these defect structures, we analyzed the formation energies of defects. The formation energy is calculated by the formula49
simulated the different configurations of H-adsorption around the defects. By the analysis of electronic properties of defect structures, the atomic mechanism of interaction between H and defects was explored. Finally, with the relative free energy of H at the absorption state as the indicator and Sabatier principle, we analyzed the effect of different defects in four materials on HER catalytic activity. These results indicate that defect engineering, especially the B-doping, is an effective method to activate the basal plane of PdSe2, PtSe2, PdTe2, and PtTe2 and make them excellent HER catalysts.
2. CALCULATION METHODS AND THEORETICAL MODELS We carried out the density functional theory calculations by using the Vienna ab initio simulation package.46 The generalized gradient approximation (GGA) of the parameterization of Perdew−Burke−Ernzerhof (PBE) was used as the exchange− correlation functional.47 The kinetic energy cutoff was set to 500 eV. The k-point grid was generated with the spacing of 0.02 Å−1 under Monkhorst−Pack scheme.48 The criterion of energy convergence was set to be 10−5 eV. All the atomic relaxation was terminated until the Hellmann−Feynman forces were smaller than 0.01 eV/Å. The vacuum layer was set to be larger than 18 Å, enough to separate the neighboring layers. The primitive cells of monolayer PdSe2, PtSe2, PdTe2, and PtTe2 are relaxed to the equilibrium structures. All the calculated structural parameters and electronic properties are shown in Table 1. The calculated lattice constants are consistent with the
Ef = E D − E P + Δni ∑ μi i
where ED and EP are the total energies of the monolayer dichalcogenides with defect structure and pristine structure in the same supercell, respectively. μi is the chemical potential of atom type i and Δni is the difference of number of atom type i in the pristine structure and defect structure. With PdSe2 as an example, we considered Se as the experimental parameter to analyze the formation of these defects. Under the thermodynamic equilibrium, the chemical potential of Se (μSe) is set in the range of [μSe(bulk) + ΔHf/2, μSe(bulk)]. Here, ΔHf is the formation heat of PdSe2 and defined by the formula, ΔHf = EPdSe2 − EPd − 2ESe, in which EPdSe2, EPd, and ESe are the total energies of singlelayer PdSe2, bulk Pd, and bulk S. The upper limit of μSe corresponds to the Se-rich condition and the down limit corresponds to the Pd-rich condition. For the B-doping, the chemical potential of B (μB) is set to that of bulk α-B. To get an insight into the HER catalytic activity by the interaction between H and the catalyst, we analyzed the adsorption energy on the potential active sites of the surface. The adsorption energy is defined by the formula
Table 1. Structural Parameters Including Lattice Constant a (Angstrom) and Bond Length bM−X (Angstrom) between Metal Atom and Chalcogen, Formation Energy Ef (eV/fu), and Band Gap Eg (Electronvolts) at GGA/PBE Level materials
a (Å)
bM−X (Å)
Ef (eV/fu)
Eg (eV)
PtSe2
3.77 3.73 (ref 45) 4.02 4.03 (ref 45) 3.74 4.03
2.53
−1.51
1.36
2.71
−1.10
0.75
2.53 2.70
−1.07 −1.00
0.73 0.23
PtTe2 PdSe2 PdTe2
(1)
ΔEads = E host + H − E host − E H
(2)
Figure 1. Structural representation of monolayer PtSe2 with (a) pristine structure and different kinds of defects including (b) single vacancy of metal atom (VPt), (c) single vacancy of nonmetallic atom (VSe), (d) double vacancy (DVSe), and (e) the B-doping (BSe). Note that the numbers around the defect represent the potential adsorption positions of H around defects considered in this work. The structures of defect models in PdSe2, PdTe2, and PtTe2 are similar to that in PtSe2. 10059
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Figure 2. Defect formation energy as a function of chemical potential for different materials including (a) PdSe2, (b) PdTe2, (c) PtSe2, (d) PtTe2, and (e) formation energy of B substitution (BSe for PdSe2 and PtSe2, BTe for PdTe2 and PtTe2) as a function of chemical potential calculated on the basis of the pristine structure in Figure 1a and single-vacancy structure in Figure 1c. Note that the formation energy of B substitution calculated on the basis of single-vacancy structure does not change by following the chemical potential of Te (Se) in (e).
hinder the HER rate.6,50,51 According to Sabatier principle, the optimal value should be a thermoneutral value, ΔGH* ≈ 0. The theoretical exchange current density (i0) is calculated on the basis of ΔGH*. The theoretical exchange current density can reveal the reaction rate during the proton transfer to the surface to some extent.6 If the proton transfer is exothermic (ΔGH* < 0), the exchange current expression at standard conditions with pH = 0 and T = 300 K is
where Ehost+H and Ehost are the total energies of substrate material with and without H-adsorption, respectively. EH denotes the energy of isolated H atom. The total HER can be expressed as 2H+ + 2e− → H2. At equilibrium state, the free energy of the initial state and the final state in the reaction should be equivalent. Therefore, the free energy of the intermediate state H* (H adsorbed on the active site of catalyst) is important for the reaction rate. As an important indicator of the HER activity, the relative free energy of H* with the initial state or the finial state as the reference can be expressed as 1 ΔG H * = Ecat + H − Ecat − 2 E H2 + ΔEZPE − T ΔS , w h e r e Ecat+H and Ecat are the total energies of the catalysts with and without H-adsorption, respectively. EH2 is the total energy of H2 molecule. ΔEZPE is the difference of zero-point energies between the intermediate H* and the finial state. ΔS is the entropy difference of both states. Following the work of Nørskov et al., the contribution of vibrational entropy from H in the intermediate H* is small and can be ignored.6 ΔS can be calculated on the basis of the entropy of gas phase at standard conditions and TΔS at 300 K is about −0.2 eV. The contribution of ΔEZPE to free energy for H-adsorption is usually small and about 0.04 eV for H on Cu(111) surface. Therefore, the relative free energy can be approximately calculated by the formula6 ΔG H * = Ecat + H − Ecat −
1 E H + 0.24 2 2
i0 = −ek 0[1 + exp( −ΔG H */kT )]−1
(4)
By contrast, if the reaction is endothermic (ΔGH* > 0), the exchange current density is calculated by i0 = −ek 0 exp( −ΔG H */kT )[1 + exp( −ΔG H */kT )]−1 (5) −1
where k0 is the rate constant (200 s /site) and k is Boltzmann constant.
3. RESULTS AND DISCUSSION 3.1. Defects and B-Doping. In 2D materials, vacancy as a typical point defect is popular. We analyzed two kinds of single vacancies in PdSe2, PtSe2, PdTe2, and PtTe2, as shown in Figure 2. From the formation energy, whatever the condition of Pd-rich (Pt-rich) or Se-rich (Te-rich), the single-vacancy VSe (VTe) is more stable than VPd (VPt). It is also noticed that these nonmetal vacancies have low formation energy (less than 2 eV). This implies that they are a common type of defects in the process of experimental synthesis, especially under the condition of rich Pd to synthesize PdTe2.
(3)
For ΔGH*, the positive value will obstruct the adsorption process and the negative value will restrict the desorption. Both cases 10060
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strong, especially in PdSe2. Meanwhile, the interaction strength between H and other types of defects is similar. It is noticed that the interaction between H and the defects is stronger than that of H and pristine PdSe2 (PtSe2, PdTe2, and PtTe2). To understand the atomic mechanism of interaction between H and the defects, we analyzed the change in electronic properties due to the defects. Taking PdSe2 for example, the density of states (DOS) and partial density of states (PDOS) of VPd, VSe, VSe2, and BSe are plotted in Figure 4. The electronic band structure in Figure S2a demonstrates that pristine PdSe2 is a semiconductor with a band gap of about 0.7 eV. For VPd in Figure 4a, a quasi-localized state appears in the region of band gap. Fermi level is anchored at the middle of quasi-localized state. From the PDOS, this defect state can be attributed to the Se near VPd. To observe the distribution of charge in real space, we plotted the differential charge density in Figure 5. As shown in Figure 5a, from the charge distribution, the polarized covalent bond is formed between Pd and Se atom with the surplus charge transferred from Pd to Se. With VPd, there is charge accumulation near the unsaturated Se atom near the vacancy. With the H-adsorption near the defect, the hydrogen interacts with the localized electronic states from Se near VPd, as shown in Figures S1a and S3a. In addition, H also traps the other Se atom near VPd in PdSe2, resulting in the weakening of the Pd−Se bond near VPd. This phenomenon is not observed in other three compounds (Figure S4). It may be the reason why the absorption strength at VPd of PdSe2 is the largest. The localized states with high PDOS, such as the edge states from S edge-atoms in MoS2, can strengthen the interaction between H and defect. However, for the metal vacancy (VPd and VPt) in PdSe2, PtSe2, PdTe2, and PtTe2, the interaction is too strong to favor the HER based on Sabatier principle. For the VSe and DVSe in PdSe2, the weak localized states with lower PDOS is found to be formed, as shown in Figure 4b,c. With the participation of localized states, the H is adsorbed on Pb atom near the vacancy results in the appropriate interaction between H and defects (Figures S1 and S3). In Figure 5b,c, it is observed that there is a little charge accumulation near the vacancy. For BSe, the weak localized states from the contribution of Pd near B atom (Figure 4d) induce the accumulation of charges near the B atom (Figure 5d). With the H-adsorption, the localized state is modulated obviously with the charge transfer in Figure S3d. In addition, it is noticed there is a trend of charge transfer from defects to H with charge polarization in the three cases, VSe, DVSe, and BSe (Figure S1b−d). This is different from the mechanism of H-adsorption on pristine basal plane where the electron charge is transferred from H to adsorption site and its nearby sites, as shown in Figure S5. 3.3. HER Activity on Defective Structures. The relative Gibbs free energy (ΔGH*) of H-adsorption state H* with the gas phase as a reference state is an important indicator to assess the catalytic activity of catalysts. Here, we adopt ΔGH* to access the HER activity of the four materials with different defect types. As the value of ΔGH* approaches zero, the HER activity will become the best. First, we analyze the reaction activity of pristine basal plane. For PdSe2, PtSe2, PdTe2, and PtTe2, the values of ΔGH* are 0.94, 1.38, 1.10, and 1.44 eV, respectively. These large positive values imply that the HER activity of these pristine basal planes are not good. Therefore, the favorable HER activity in experiments of similar materials, such as MoS2, is usually attributed to the contribution of edge states from the edges of 2D materials.
Compared to the single vacancy VSe (or VTe), the formation of double vacancy (DVSe or DVTe) is a little difficult. In addition, in Figure 2, it is found that the isolated single vacancies are more popular than one double vacancy by comparing the formation energies of one double vacancy DVSe (DVTe) and two isolated single vacancies (V2Se or V2Te ) at the same Se (Te) concentration. This suggests the single vacancy VSe (VTe) is dominant in PdSe2, PtSe2, PdTe2, and PtTe2. For the B-doping, the popular way is the replacement of Se (Te) by B because B is easier to bond with Pt (Pd) than with Se (Te). The formation energy was calculated as presented in Figure 2e. For the four layered-compounds we considered, in Brich condition, the B substitution becomes possible due to the low formation energy. Especially, in PtTe2, the formation energy of BTe is less than 1.8 eV. It is also possible that B will occupy the single vacancy VSe (VTe) because it is popular in the synthesis processes. With the single vacancy VSe (VTe), we found that B would likely be absorbed on the vacancy to form the defect BTe (BSe). Especially, in PtSe2, the formation energy is very low and less than 0.2 eV. 3.2. H-Adsorption and Electronic Properties of Defective Structures. To consider the adsorption in the proposed four kinds of defective models, we analyzed all the possible adsorption sites with the consideration of structural symmetry for each defective model. These adsorption sites are marked by a number, as shown in Figure 1. The results are listed in Table S1. For the pristine structure, the most stable adsorption site of H is at the top of Se (Te) atom for all the considered materials. For the VPd (VPt) model, the adsorbed H atom is located at the Se (Te) atom near VPd (VPt), except PdSe2. For the VSe (VTe) model, the adsorbed H atom tends to occupy the top site of the Pd (Pt) atom near VSe (VTe). In the case of double-vacancy DVSe (DVTe) model, there are two kinds of Pd (Pt) atoms near DVSe (DVTe), which are four-coordinated and five-coordinated, respectively. The adsorbed H atom is located at the middle site of the double vacancy and the H atom prefers to bind with four-coordinated Pd (Pt) atom, as shown in Figure S1c. For the B-doping model, H atom is adsorbed above the bridge site between B and Pd (Pt). For each model in four compounds, the adsorption energy of most stable adsorption configuration is demonstrated in Figure 3. From the adsorption energies of hydrogen on different materials with various defects, we come to a conclusion that the adsorption energy of VPd (VPt) is the largest among the considered various defect types. It means that the interaction between Se (Te) near the defect and H in the VPd (VPt) model is
Figure 3. Adsorption energy of H for monolayer PdSe2, PtSe2, PdTe2, and PtTe2 with various defects in the most stable configuration. 10061
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Figure 4. Density of states (DOS) and partial density of states (PDOS) of PdSe2 with various defects including (a) VPd, (b) VSe, (c) VSe2, and (d) BSe.
Figure 5. Differential charge density of PdSe2 with various defects including (a) VPd, (b) VSe, (c) VSe2, and (d) BSe. Note that dark red color indicates charge accumulation and green color denotes charge depletion.
The calculated ΔGH* values of various materials considered with various defects are shown in Figure 6a. Compared with the pristine basal plane, these point defects can decrease significantly the Gibbs free energy of H-adsorption and thus greatly improve the catalytic activity, except the VPd and VPt in PdSe2 and PtSe2. The calculated ΔGH* of Pd (Pt) vacancy in PdSe2 and PtSe2 is very negative and indicates the interaction between H and substrate materials is too strong to release H2 effectively. Compared to T′-MoS2, the ΔGH* value of Se (Te) vacancy in
the case of PdSe2 and PdTe2 is a little large. The large positive value of ΔGH* implies that the weak binding of H with the catalyst will impede the Volmer adsorption process. For the rest of defect models in the considered four materials, especially for the B-doping, the calculated ΔGH* values are close to the thermoneutral, suggesting the superior HER catalytic activity. To further directly compare the HER catalytic activity of different defect models in the four materials, the theoretical exchange current density (i0) is calculated on the basis of ΔGH*. 10062
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Figure 6. (a) Values of ΔGH* and (b) volcano curve between the exchange current density i0 and ΔGH* for monolayer PdSe2, PtSe2, PdTe2, and PtTe2 with various defects.
Figure 7. (a) Values of ΔGH* for VSe, DVSe, and BSe as a function of defect concentration for monolayer PdSe2. (b) Volcano curve between the exchange current density i0 and ΔGH* for defective PdSe2 with different concentration of defects.
the double vacancy DVSe also has a superior activity and resides near the top site. Taking PdSe2 as an example, we also check the effect of vacancy size under the condition of rich vacancies. As shown in Figure S6, with the increase in vacancy size up to quadruple vacancy, the value of ΔGH* has a decreasing trend.
The results are plotted in Figure 6b. The catalytic activity of the catalyst is reflected in the volcano curve. We can find that the double vacancy DVSe (DVTe) and B-substitution are located at the top of volcano curve and show a much higher current density. The i0 of BSe in PdSe2 and DVTe in PtTe2 are even higher than those of Pt catalyst because of the small value of ΔGH*. The results of the above analysis of the formation of defects indicate that the B-doping can improve HER activity effectively. A comparison of the overall catalytic properties of these four materials reveals that PtTe2 exhibits a slightly more superior activity than other materials. Defect concentration may have an important effect on the HER activity, whereas a higher defect concentration means more active sites on the basal plane. To take PdSe2 as an example, we explore the concentration effect of defects. The ΔGH* values of PdSe2 with various defects including VSe, DVSe, and BSe was calculated as the functions of defect concentration in Figure 7a. At the low concentration less than 8%, the defect concentration does not have significant effect on the Gibbs free energy for the single vacancy VSe and double vacancy DVSe. With the increase in concentration to more than 12%, the Hadsorption strength of VSe has a trend of decrease and that of DVSe has a trend of increase. For the B-doping, the value of ΔGH* has a decreasing trend, following the increase in B concentration. The volcano curve between exchange current density and Gibbs free energy is plotted in Figure 7b. The Bdoping is located at the top of the volcano curve, which implies a moderate H-adsorption and a superior activity, especially at low concentration less than 6%. For the concentration less than 8%,
4. CONCLUSIONS We have studied the formation of defects and the modulation of electronic properties of the monolayer PdSe2, PtSe2, PdTe2, and PtTe2 by first-principle calculations. It was found that single vacancy VSe (VTe) was easier to form in Se (Te)-rich condition. In addition, B can be doped effectively into the lattice of the four compounds by the formation of BSe (BTe). We demonstrated that the catalytic activity of inert basal plane in PdSe2, PtSe2, PdTe2, and PtTe2 could be triggered efficiently through the single vacancy, double vacancy, and B-doping. This indicates that defect engineering could be used to enhance the HER activity of these compounds. The improvement in catalytic activity is found to originate from the facts that the defects can introduce quasi-localized states in the band gap and that these electronic states can interact moderately with H atom. With an overall assessment of the HER activity in terms of ΔGH* value, the activity of tellurides is found to be superior to the selenides slightly among PdSe2, PtSe2, PdTe2, and PtTe2. Moreover, Bdoping is a much more effective method to enhance the HER activity in these compounds. In short, it is a feasible strategy to activate the HER activity of platinum and palladium dichalcogenides by introducing the intrinsic defect and B10063
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(10) Tang, H.; Yin, H.; Wang, J.; Yang, N.; Wang, D.; Tang, Z. Molecular architecture of cobalt porphyrin multilayers on reduced graphene oxide sheets for high-performance oxygen reduction reaction. Angew. Chem., Int. Ed. 2013, 52, 5585−5589. (11) Li, Y.; Wang, H.; Xie, L.; Liang, Y.; Hong, G.; Dai, H. MoS2 nanoparticles grown on graphene: an advanced catalyst for hydrogen evolution reaction. J. Am. Chem. Soc. 2011, 133, 7296−7299. (12) Yu, Y.; Huang, S. Y.; Li, Y.; Steinmann, S. N.; Yang, W.; Cao, L. Layer-dependent electrocatalysis of MoS2 for hydrogen evolution. Nano Lett. 2014, 14, 553−558. (13) Cheng, L.; Huang, W.; Gong, Q.; Liu, C.; Liu, Z.; Li, Y.; Dai, H. Ultrathin WS2 nanoflakes as a high-performance electrocatalyst for the hydrogen evolution reaction. Angew. Chem., Int. Ed. 2014, 53, 7860− 7863. (14) Yin, Y.; Zhang, Y.; Gao, T.; Yao, T.; Zhang, X.; Han, J.; Wang, X.; Zhang, Z.; Xu, P.; Zhang, P.; et al. Synergistic phase and disorder engineering in 1T-MoSe2 nanosheets for enhanced hydrogen-evolution reaction. Adv. Mater. 2017, 29, No. 1700311. (15) Jia, L.; Sun, X.; Jiang, Y.; Yu, S.; Wang, C. A novel MoSe2-reduced graphene oxide/polyimide composite film for applications in electrocatalysis and photoelectrocatalysis hydrogen evolution. Adv. Funct. Mater. 2015, 25, 1814−1820. (16) Chen, X.; Wang, G. Tuning the hydrogen evolution activity of MS2 (M = Mo or Nb) monolayers by strain engineering. Phys. Chem. Chem. Phys. 2016, 18, 9388−9395. (17) Shi, J.; Wang, X.; Zhang, S.; Xiao, L.; Huan, Y.; Gong, Y.; Zhang, Z.; Li, Y.; Zhou, X.; Hong, M.; et al. Two-dimensional metallic tantalum disulfide as a hydrogen evolution catalyst. Nat. Commun. 2017, 8, No. 958. (18) Merki, D.; Hu, X. Recent developments of molybdenum and tungsten sulfides as hydrogen evolution catalysts. Energy Environ. Sci. 2011, 4, No. 3878. (19) Chia, X.; Eng, A. Y. S.; Ambrosi, A.; Tan, S. M.; Pumera, M. Electrochemistry of nanostructured layered transition-metal dichalcogenides. Chem. Rev. 2015, 115, 11941−11966. (20) Eftekhari, A. Molybdenum diselenide (MoSe2) for energy storage, catalysis, and optoelectronics. Appl. Mater. Today 2017, 8, 1− 17. (21) Velický, M.; Toth, P. S. From two-dimensional materials to their heterostructures: An electrochemist’s perspective. Appl. Mater. Today 2017, 8, 68−103. (22) Zhao, S.; Wang, Y.; Dong, J.; He, C.-T.; Yin, H.; An, P.; Zhao, K.; Zhang, X.; Gao, C.; Zhang, L.; et al. Ultrathin metal−organic framework nanosheets for electrocatalytic oxygen evolution. Nat. Energy 2016, 1, No. 16184. (23) Yin, H.; Tang, Z. Ultrathin two-dimensional layered metal hydroxides: an emerging platform for advanced catalysis, energy conversion and storage. Chem. Soc. Rev. 2016, 45, 4873. (24) Yin, H.; Zhao, S.; Zhao, K.; Muqsit, A.; Tang, H.; Chang, L.; Zhao, H.; Gao, Y.; Tang, Z. Ultrathin platinum nanowires grown on single-layered nickel hydroxide with high hydrogen evolution activity. Nat. Commun. 2015, 6, No. 6430. (25) Guo, J.; Zhang, Y.; Zhu, Y.; Long, C.; Zhao, M.; He, M.; Zhang, X.; Lv, J.; Han, B.; Tang, Z. Ultrathin chiral metal−organic-framework nanosheets for efficient enantioselective separation. Angew. Chem., Int. Ed. 2018, 57, 6873−6877. (26) Fan, X.; Zheng, W. T.; Kuo, J.-L.; Singh, D. J.; Sun, C. Q.; Zhu, W. Modulation of electronic properties from stacking orders and spin-orbit coupling for 3R-type MoS2. Sci. Rep. 2016, 6, No. 24140. (27) Fan, X.; Chang, C. H.; Zheng, W. T.; Kuo, J.-L.; Singh, D. J. The electronic properties of single-layer and multilayer MoS2 under high pressure. J. Phys. Chem. C 2015, 119, 10189−10196. (28) Splendiani, A.; Sun, L.; Zhang, Y.; Li, T.; Kim, J.; Chim, C.-Y.; Galli, G.; Wang, F. Emerging photoluminescence in monolayer MoS2. Nano Lett. 2010, 10, 1271−1275. (29) Tan, S. M.; Ambrosi, A.; Sofer, Z.; Huber, Š ; Sedmidubský, D.; Pumera, M. Pristine basal- and edge-plane-oriented molybdenite MoS2 exhibiting highly anisotropic properties. Chem. - Eur. J. 2015, 21, 7170− 7178.
doping. It is also expected that these results may shed some light on improving the HER activity of other TMDs.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01414. Adsorption energy of H in different configurations; charge density redistribution of PdSe2 with various defects; band structure of PdSe2, PtSe2, PdTe2, and PtTe2; density of states and partial density of states of PdSe2 with various defects; charge density redistribution of PdSe2, PdTe2, PtSe2, and PtTe2 with single vacancy of metal atom due to H-adsorption; density of states of PtTe2 with Hadsorption and without H-adsorption and charge density redistribution of PtTe2 due to H-adsorption; value of ΔGH* as a function of vacancy size for PdSe2 with different Se vacancies (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail: xff
[email protected]. ORCID
Xiaofeng Fan: 0000-0001-6288-4866 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The research was supported by the National Key R&D Program of China (Grant No. 2016YFA0200400) and the National Natural Science Foundation of China (Grant Nos. 11504123 and 51627805).
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REFERENCES
(1) Gasteiger, H. A.; Kocha, S. S.; Sompalli, B.; Wagner, F. T. Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Appl. Catal., B 2005, 56, 9−35. (2) Turner, J. A. Sustainable hydrogen production. Science 2004, 305, 972−974. (3) Lu, Q.; Yu, Y.; Ma, Q.; Chen, B.; Zhang, H. 2D transition-metaldichalcogenide-nanosheet-based composites for photocatalytic and electrocatalytic hydrogen evolution reactions. Adv. Mater. 2016, 28, 1917−1933. (4) Jiao, Y.; Zheng, Y.; Jaroniec, M.; Qiao, S. Z. Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. Chem. Soc. Rev. 2015, 44, 2060−2086. (5) Yan, H.; Tian, C.; Wang, L.; Wu, A.; Meng, M.; Zhao, L.; Fu, H. Phosphorus-modified tungsten nitride/reduced graphene oxide as a high-performance, non-noble-metal electrocatalyst for the hydrogen evolution reaction. Angew. Chem., Int. Ed. 2015, 54, 6325−6329. (6) Nørskov, J. K.; Bligaard, T.; Logadottir, A.; Kitchin, J. R.; Chen, J. G.; Pandelov, S.; Stimming, U. Trends in the exchange current for hydrogen evolution. J. Electrochem. Soc. 2005, 152, J23−J26. (7) Yin, H.; Zhao, S.; Zhao, K.; Muqsit, A.; Tang, H.; Chang, L.; Zhao, H.; Gao, Y.; Tang, Z. Ultrathin platinum nanowires grown on singlelayered nickel hydroxide with high hydrogen evolution activity. Nat. Commun. 2015, 6, No. 6430. (8) Trasatti, S. Work function, electronegativity, and electrochemical behaviour of metals: III. Electrolytic hydrogen evolution in acid solutions. J. Electroanal. Chem. Interfacial Electrochem. 1972, 39, 163− 184. (9) Liu, J.; Fan, X.; Sun, C. Q.; Zhu, W. DFT study on bimetallic Pt/ Cu(1 1 1) as efficient catalyst for H2 dissociation. Appl. Surf. Sci. 2018, 441, 23−28. 10064
DOI: 10.1021/acsomega.8b01414 ACS Omega 2018, 3, 10058−10065
ACS Omega
Article
(30) Hinnemann, B.; Moses, P. G.; Bonde, J.; Jørgensen, K. P.; Nielsen, J. H.; Horch, S.; Chorkendorff, I.; Nørskov, J. K. Biomimetic hydrogen evolution: MoS2 nanoparticles as catalyst for hydrogen evolution. J. Am. Chem. Soc. 2005, 127, 5308−5309. (31) Jaramillo, T. F.; Jørgensen, K. P.; Bonde, J.; Nielsen, J. H.; Horch, S.; Chorkendorff, I. Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts. Science 2007, 317, 100−102. (32) Zhang, Y.; Gong, Q.; Li, L.; Yang, H.; Li, Y.; Wang, Q. MoSe2 porous microspheres comprising monolayer flakes with high electrocatalytic activity. Nano Res. 2015, 8, 1108−1115. (33) Chen, Z.; Cummins, D.; Reinecke, B. N.; Clark, E.; Sunkara, M. K.; Jaramillo, T. F. Core-shell MoO3-MoS2 nanowires for hydrogen evolution: a functional design for electrocatalytic materials. Nano Lett. 2011, 11, 4168−4175. (34) Voiry, D.; Salehi, M.; Silva, R.; Fujita, T.; Chen, M.; Asefa, T.; Shenoy, V. B.; Eda, G.; Chhowalla, M. Conducting MoS2 nanosheets as catalysts for hydrogen evolution reaction. Nano Lett. 2013, 13, 6222− 6227. (35) Ouyang, Y.; Ling, C.; Chen, Q.; Wang, Z.; Shi, L.; Wang, J. Activating inert basal planes of MoS2 for hydrogen evolution reaction through the formation of different intrinsic defects. Chem. Mater. 2016, 28, 4390−4396. (36) Gao, G.; Sun, Q.; Du, A. Activating catalytic inert basal plane of molybdenum disulfide to optimize hydrogen evolution activity via defect doping and strain engineering. J. Phys. Chem. C 2016, 120, 16761−16766. (37) Fan, X.-L.; Yang, Y.; Xiao, P.; Lau, W.-M. Site-specific catalytic activity in exfoliated MoS2single-layer polytypes for hydrogen evolution: basal plane and edges. J. Mater. Chem. A. 2014, 2, 20545− 20551. (38) Shu, H.; Zhou, D.; Li, F.; Cao, D.; Chen, X. Defect engineering in MoSe2 for the hydrogen evolution reaction: from point defects to edges. ACS Appl. Mater. Interfaces 2017, 9, 42688−42698. (39) Putungan, D. B.; Lin, S. H.; Kuo, J. L. A first-principles examination of conducting monolayer 1T′-MX2 (M = Mo, W; X = S, Se, Te): promising catalysts for hydrogen evolution reaction and its enhancement by strain. Phys. Chem. Chem. Phys. 2015, 17, 21702− 21708. (40) Li, H.; Tsai, C.; Koh, A. L.; Cai, L.; Contryman, A. W.; Fragapane, A. H.; Zhao, J.; Han, H. S.; Manoharan, H. C.; Abild-Pedersen, F.; et al. Corrigendum: Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies. Nat. Mater. 2016, 15, 48−53. (41) Deng, J.; Li, H.; Xiao, J.; Tu, Y.; Deng, D.; Yang, H.; Tian, H.; Li, J.; Ren, P.; Bao, X. Triggering the electrocatalytic hydrogen evolution activity of the inert two-dimensional MoS2 surface via single-atom metal doping. Energy Environ. Sci. 2015, 8, 1594−1601. (42) Liu, G.; Robertson, A. W.; Li, M. M.; Kuo, W. C. H.; Darby, M. T.; Muhieddine, M. H.; Lin, Y. C.; Suenaga, K.; Stamatakis, M.; Warner, J. H.; et al. MoS2 monolayer catalyst doped with isolated Co atoms for the hydrodeoxygenation reaction. Nat. Chem. 2017, 9, 810−816. (43) Gao, D.; Xia, B.; Zhu, C.; Du, Y.; Xi, P.; Xue, D.; Ding, J.; Wang, J. Activation of the MoSe2 basal plane and Se-edge by B doping for enhanced hydrogen evolution. J. Mater. Chem. A 2018, 6, 510−515. (44) Liu, P.; Zhu, J.; Zhang, J.; Xi, P.; Tao, K.; Gao, D.; Xue, D. P Dopants triggered new basal plane active sites and enlarged interlayer spacing in MoS2 nanosheets toward electrocatalytic hydrogen evolution. ACS Energy Lett. 2017, 2, 745−752. (45) Chia, X.; Adriano, A.; Lazar, P.; Sofer, Z.; Luxa, J.; Pumera, M. Layered platinum dichalcogenides (PtS2, PtSe2, and PtTe2) electrocatalysis: monotonic dependence on the chalcogen size. Adv. Funct. Mater. 2016, 26, 4306−4318. (46) Kresse, G.; Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 1996, 54, 11169−11186. (47) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77, 3865−3868.
(48) Monkhorst, H. J.; Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 1976, 13, 5188−5192. (49) Liu, X.; Wei, Z.; Liu, J.; Tan, W.; Fang, X.; Fang, D.; Wang, X.; Wang, D.; Tang, J.; Fan, X. Oxidization of Al0.5Ga0.5As(001) surface: The electronic properties. Appl. Surf. Sci. 2018, 436, 460−466. (50) Parsons, R. The rate of electrolytic hydrogen evolution and the heat of adsorption of hydrogen. Trans. Faraday Soc. 1958, 54, 1053− 1063. (51) Greeley, J.; Jaramillo, T. F.; Bonde, J.; Chorkendorff, I. B.; Norskov, J. K. Computational high-throughput screening of electrocatalytic materials for hydrogen evolution. Nat. Mater. 2006, 5, 909− 913.
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