Enhanced Electrocatalytic Reduction of CO2 via Chemical Coupling

May 28, 2019 - The reaction rates for the CO2 electroreduction into formate on these catalysts have ..... The authors declare no competing financial i...
0 downloads 0 Views 3MB Size
Download PDF
Letter Cite This: Nano Lett. 2019, 19, 4029−4034

pubs.acs.org/NanoLett

Enhanced Electrocatalytic Reduction of CO2 via Chemical Coupling between Indium Oxide and Reduced Graphene Oxide Zhirong Zhang,†,∥ Fawad Ahmad,†,∥ Wanghui Zhao,†,∥ Wensheng Yan,† Wenhua Zhang,*,† Hongwen Huang,*,§ Chao Ma,§ and Jie Zeng*,† †

Downloaded via IDAHO STATE UNIV on July 17, 2019 at 14:55:19 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Hefei National Laboratory for Physical Sciences at the Microscale, Key Laboratory of Strongly-Coupled Quantum Matter Physics of Chinese Academy of Sciences, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China § College of Materials Science and Engineering, Hunan University, Changsha, Hunan 410082, P.R. China S Supporting Information *

ABSTRACT: The chemical coupling interaction has been explored extensively to boost heterogeneous catalysis, but the insight into how chemical coupling interaction works on CO2 electroreduction remains unclear. Herein we demonstrate how the chemical coupling interaction between porous In2O3 nanobelts and reduced graphene oxide (rGO) could substantially improve the electrocatalytic activity toward CO2 electroreduction. Such an In2O3−rGO hybrid catalyst showed 1.4-fold and 3.6-fold enhancements in Faradaic efficiency and specific current density for the formation of formate at −1.2 V versus reversible hydrogen electrode relative to the catalyst prepared by physically loading of In2O3 nanobelts onto rGO, respectively. The density functional theory calculations and electrochemical analysis together revealed that the chemical coupling interaction boosted CO2 electroreduction activity by improving electrical conductivity and stabilizing key intermediate HCOO−*. The present work not only deepens an understanding of chemical coupling effect but also provides an effective lever to optimize the catalytic performance toward CO2 electroreduction. KEYWORDS: Chemical coupling interaction, CO2 electroreduction, electrical conductivity, adsorption energy

E

composed of Co3O4 nanoparticles grown on reduced graphene oxide (rGO) displayed largely enhanced activity and durability toward both the oxygen reduction reaction and oxygen evolution reaction relative to Co3O4 or graphene oxide alone.20 The synergy between Co3O4 and rGO accounted for such improvements. In another case, the effect of chemical coupling interaction between polyaniline nanodots and CoP nanowires on the improved electrocatalytic activity of hybrid electrocatalyst was assigned to the improved electron conductivity.21 Most of the previous investigations on the chemical coupling were concerned with the synergetic effect between the different components in the hybrid but ignored the change in electronic structure of the catalytically active

lectroreduction of CO2 powered by renewable electricity offers a promising approach to simultaneously mitigate the climate issue and store the intermittent energy sources by transforming CO2 to value-added chemicals/fuels.1−7 However, enabling an efficient electroreduction of CO2 remains an open challenge owing to the great difficulty to activate the stable CO2 molecule.8,9 Finding active and selective electrocatalysts thus holds the key to realize the economically viable conversion of CO2. Thanks to tremendous efforts from many research groups, the catalytic activity and selectivity of various electrocatalysts, including metals, metal oxides/chalcogenides, carbonaceous materials, and so on, at present can be optimized via the size effect, alloy effect, strain effect, sharp-tip effect, oxygen vacancy effect, and so forth.10−19 The chemical coupling between different components in a hybrid material offers great opportunities to improve the catalytic properties.20−23 For example, a hybrid catalyst © 2019 American Chemical Society

Received: April 4, 2019 Revised: May 14, 2019 Published: May 28, 2019 4029

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034

Letter

Nano Letters

Figure 1. Formation process and structural characterizations. (a) Schematic illustration shows the preparation procedure for the In2O3−rGO hybrid. (b) Low-magnification TEM image. (c) High-magnification TEM image. (d) Atomic-resolution HAADF-STEM image. The inset shows the corresponding FFT pattern. (e) C K-edge XANES spectra of In2O3−rGO hybrid and rGO. (f) In M2-edge XANES spctra of In2O3−rGO hybrid and In2O3 nanobelts. (g) In 3d XPS spectra of In2O3−rGO hybrid and In2O3 nanobelts.

that the porous In2O3 nanobelts were uniformly grown onto the rGO nanosheets. The total In2O3 content in the hybrid was estimated to be 58.0 wt % by the inductively coupled plasma atomic emission spectrum (ICP-AES). The atomic-level structural information on the In2O3−rGO hybrid was further analyzed by atomic-resolution high-angle annular dark-field scanning TEM (HAADF-STEM) (Figure 1d). The continuous lattice fringes and the corresponding fast Fourier transform (FFT) pattern confirmed the monocrystalline nature of the porous In2O3 nanobelts. Agreeing well with the X-ray diffraction (XRD) pattern shown in Figure S3, the lattice fringes matched well with the crystal planes of cubic In2O3 (space group Ia3̅, a = 10.118 Å). The exposed surface facet of porous In2O3 nanobelts was further determined as the {110} plane of cubic In2O3. For comparison, we also prepared the porous In2O3 nanobelts using the similar procedure together with a physical mixture of In2O3 nanobelts and rGO (denoted as In2O3/rGO) (Figures S4 and S5). The structural characterizations indicated that the morphology of the produced porous In2O3 nanobelts was identical to that of porous In2O3 nanobelts in the hybrid. The thickness of porous In2O3 nanobelts was estimated to be 1.4 nm by atomic force microscopy (AFM) (Figure S6). Given almost the same morphology of In2O3 component in these three samples, we could guess the porous In2O3 nanobelts in the hybrid also presented the feature of ultrathin thickness. The interaction between the porous In2O3 nanobelts and rGO nanosheets in the hybrid was revealed by X-ray absorption near edge structure (XANES) and X-ray photo-

phase. Moreover, the fundamental understanding of the chemical coupling interaction in the CO2 electroreduction remains relatively vague. Herein, we demonstrate the chemical coupling interaction between porous In2O3 nanobelts and rGO could modify the electron structure of In2O3 and substantially improve its electrocatalytic activity toward CO2 reduction. We further reveal the chemical coupling effect on CO2 electroreduction by combing density functional theory (DFT) calculations and electrochemical analysis. The porous In2O3 nanobelts−rGO hybrid (denoted as In2O3−rGO hybrid) was fabricated via a two-step method, as schematically shown in Figure 1a. In the first step, an aqueous solution containing a certain amount of commercial GO nanosheets, sodium oleate, and indium(III) chloride was subjected to a hydrothermal treatment at 150 °C for 3 h to produce the In(OH)3 nanobelts−rGO hybrid. Afterward, the preformed In(OH)3 nanobelts−rGO hybrid was annealed in air at 400 °C for 5 min to obtain the In2O3−rGO hybrid. The structural characterizations for intermediate products obtained after the hydrothermal process demonstrated the formation of In(OH)3 nanobelts−rGO hybrid (Figure S1). After the annealing treatment, the Raman spectrum with typical Raman peaks of In2O3 at 303, 360, 491, and 625 cm−1 suggested the formation of In2O3.24 Meanwhile, the characteristic D- and G-band at 1350 and 1600 cm−1 as well as the intensity ratio of ID/IG (about 1.0) validated the presence of rGO (Figure S2). The above results confirmed the production of In2O3−rGO hybrid. The representative transmission electron microscopy (TEM) images (Figure 1b,c) displayed 4030

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034

Letter

Nano Letters

Figure 2. Performance of In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts for electrochemical reduction of CO2. (a) FEs of CO and formate for In2O3−rGO hybrid (blue), In2O3/rGO (olive green), and In2O3/C (red) catalysts. (b) Current density of formate based on the electrode’s geometric surace area. (c) ECSA-normalized current density of formate. (d) Long-term durability of In2O3−rGO hybrid at −1.2 V for 10 h.

−0.5 to −1.2 V versus reversible hydrogen electrode (vs RHE) (all the potentials are referred to RHE in this work) for these catalysts (Figure S9). Figure 2a shows that the total Faradaic efficiencies (FEs) for the formation of formate and CO on In2O3−rGO hybrid catalyst exceeded 90% when the applied potential was more negative than −0.6 V, much higher than the corresponding FEs on In2O3/C and In2O3/rGO catalysts. The maximum FE for formate, the major product, reached 84.6% at −1.2 V for In2O3−rGO hybrid catalyst, which was 1.8 and 1.4 times greater than that on In2O3/C (48.2% at −1.2 V) and In2O3/rGO (61.9% at −1.2 V) catalysts, respectively. Furthermore, the In2O3−rGO hybrid catalyst exhibited a largely enhanced partial formate current density (Figure 2b). It should be noted that the FE and partial current density for the formation of formate reported in this work surpass most of the reported remarkable catalysts (Table S2). The specific activities of the catalysts for the formation of formate were also determined by normalizing the corresponding current density against the electrochemically active surface areas (ECSAs) of catalysts. The ECSAs of In2O3−rGO hybrid (25.5 m2/g), In2O3/rGO (41.4 m2/g, and In2O3/C (34.6 m2/ g) catalysts were calculated by double-layer capacitance measurements (Figure S10). We then derived the specific activities of In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts for formate production at various potentials, demonstrating 5.3 and 3.6 times higher specific activity of the In2O3−rGO hybrid catalyst than that of In2O3/C and In2O3/rGO catalyst at −1.2 V (Figure 2c). It should be noted that the estimated ECSAs of In2O3−rGO hybrid and In2O3/ rGO catalysts from double-layer capacitance measurements included the electrochemical active surface areas of both In2O3 and rGO. Thus, the calculated specific activities of these two

electron spectroscopy (XPS). The carbon K-edge XANES spectrum collected from In2O3−rGO hybrid presented a heightened CO π* peak at 288.6 eV relative to the corresponding peak of rGO, which demonstrated the presence of chemical coupling interaction between In2O3 and rGO via COIn bonds (Figure 1e).22 The formation of the C O−In bonding changed the π* orbitals of carbon ring structure and thus led to a decreased peak in the range of 285− 286 eV.22 Moreover, In M2-edge XANES spectra of In2O3− rGO hybrid showed a declining intensity compared with that of In2O3, indicating the electron transfer from rGO to In2O3 originated from the strong interactions between In2O3 and rGO (Figure 1f). The shifted In 3d XPS peaks of In2O3−rGO hybrid also coincided with this trend (Figure 1g). In contrast, In2O3/rGO exhibited negligible interactions between In2O3 and rGO with no prominent changes in its In 3d XPS peaks relative to pure In2O3 (Figure S7). The electrocatalytic properties of In2O3−rGO hybrid toward CO2 reduction were then evaluated in comparison with porous In2O3 nanobelts (denoted as In2O3/C) as well as In2O3/rGO. The linear sweep voltammetric (LSV) curves in Figure S8 revealed the negligible electrocatalytic activity of the rGO nanosheets, confirming that the In2O3 was the active phase toward CO2 electroreduction. Moreover, the In2O3−rGO hybrid catalyst exhibited the highest reduction current when compared with other catalysts in the CO2-saturated electrolyte, hinting of the improved activity of the In2O3−rGO hybrid catalyst. Controlled-potential electrolysis of CO2 was further carried out to quantify the products obtained at different applied potentials. The 1H nuclear magnetic resonance (1H NMR) and gas chromatography (GC) analyses identified the formation of formate, CO, and H2 in the potential range from 4031

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034

Letter

Nano Letters

Figure 3. DFT calculation. (a) The differential charge diagram of In2O3−rGO hybrid catalyst. Yellow represents the electron accumulation area, blue represents the electron loss area. (b) Gibbs free energy diagrams for CO2 reduction to formate on In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts.

Figure 4. Electrokinetics of CO2 reduction to formate over In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts. (a) Tafel plots in CO2saturated 0.1 M KHCO3 electrolyte. (b) Partial current density of formate versus HCO3− concentration at a potential of −1.2 V.

of 154, 180, and 206 Ω for In2O3−rGO hybrid, In2O3/rGO, and In2O3/C, respectively. The lowest Rct value of In2O3−rGO hybrid suggests it is the best electrical conductivity among the three samples. The reason for the reduction in interfacial charge-transfer resistance is probably related to the more delocalized electrons in In2O3−rGO hybrid due to the electron transfer from rGO to In2O3 resulting from the strong chemical coupling interaction between In2O3 and rGO. Although the favored interfacial charge transfer would facilitate the CO2 reduction, it is believed that the slightly improved interfacial charge-transfer resistance cannot completely account for the 5.3-fold enhancement in specific activity. DFT calculations were further performed to investigate the variations in electronic structure and adsorption of reaction intermediates on In2O3 induced by the chemical coupling interaction between In 2 O 3 and rGO (see Supporting Information for details). Prior to determination of the Gibbs free energy diagrams, we first calculated the charge redistribution in In2O3−rGO hybrid and In2O3/rGO. The physically mixed In2O3 and rGO showed only a transfer of 0.13 electrons, whereas In2O3 and rGO coupled by chemical interaction presented a donation of 0.59 electrons from rGO nanosheets to In2O3 nanobelts (Figure 3a). The calculated results in agreement with the experimental observations suggested the higher extent of electron transfer with the presence of chemical coupling. The Gibbs free energy diagrams for CO2 reduction into formate were further calculated and clearly showed the much lower Gibbs free energy for the

catalysts were indeed underestimated. However, the enhancement factor should keep unchanged when comparing the specific activities of In2O3−rGO hybrid and In2O3/rGO catalysts due to the use of the same amount of rGO, definitely confirming the enhanced specific activity of In2O3−rGO hybrid catalyst. The long-term durability test illustrated in Figure 2d exhibited inappreciable decays in the FE and current density for the formation of formate on In2O3−rGO hybrid catalyst over 10 h, indicating its remarkable stability. The retained morphological structure after the durability test shown in Figure S11 supported the excellent stability. Besides, the repeatability of the In2O3−rGO hybrid catalyst was also verified by continually examining the CO2 electroreduction performance of the catalyst three times (Figure S12), demonstrating the excellent repeatability of the catalyst. The in-depth understanding of the improved specific activity was disclosed. Given the identical microstructure of the In2O3, the catalytically active component, for In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts, the activity enhancement may thus be attributed to the chemical coupling interaction between rGO and porous In2O3 nanobelts. From the perspective of electrocatalysis, we analyzed the changes in electrical conductivity and adsorption energies of key intermediates that caused by the chemical coupling interaction. The electrochemical impedance analysis was performed to reveal the interfacial charge transfer resistance (Rct) of the catalysts. As shown in Figure S13, the semicircle diameter of electrochemical impedance spectra corresponds to a Rct value 4032

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034

Letter

Nano Letters formation of key intermediate HCOO−* on In2O3−rGO hybrid catalyst due to the electron-rich structure (Figure S14 and Figure 3b). The trends in Gibbs free energies for HCOO−* are very consistent with the experimental trends in catalytic activities for In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts, also confirming the reasonable model construction. Besides, the protonation of CO2−* to form intermediate HCOO−* could be identified as the ratedetermining step. Under this circumstance, we can conclude that the lower Gibbs free energy for the formation of key intermediate HCOO−* is another crucial factor to reduce the overpotential and facilitate the CO2 electroreduction to generate formate on In2O3−rGO hybrid catalyst. The electrochemical microkinetic analysis was also performed to verify the rate-determining step for CO2 electroreduction on In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts. As shown in Figure 4a, the Tafel slopes of In2O3− rGO hybrid, In2O3/rGO, and In2O3/C catalysts were determined to be 67, 75, and 78 mV dec−1, which is close to the theoretical value of 59 mV dec−1, indicating the proton transfer step is the rate-determining step.25 Meanwhile the slightly lower Tafel slopes of In2O3−rGO hybrid suggests its faster reaction kinetics. Besides, electrolysis was performed in CO2-saturated KHCO3 electrolyte at −1.2 V (vs RHE) with HCO3− concentrations ranging from 0.025 to 0.5 M with KClO4 added to the electrolyte to maintain ionic strength. As showed in Figure 4b, plots of log(jHCOOH) versus log([HCO3−]) show slopes of 0.98, 0.91, and 0.87 for the In2O3−rGO hybrid, In2O3/rGO, and In2O3/C catalysts, respectively. The reaction rates for the CO2 electroreduction into formate on these catalysts have approximate first-order dependence on the concentration of HCO3−, again confirming that the proton transfer step is the rate-determining step on the three catalysts. All evidence clearly supported that the strong chemical coupling interaction in In2O3−rGO hybrid catalyst caused an improved electrical conductivity and a reduced Gibbs free energy for the formation of key intermediate HCOO−* in turn boosting the activity toward CO2 electroreduction. In summary, we have demonstrated the construction of chemical coupling interaction between porous In2O3 nanobelts and rGO could considerably enhance the catalytic activity toward CO2 electroreduction, resulting in the high FEs (more than 90%) with a potential more negative than −0.6 V. Specifically, the FE and specific current density for the formation of formate at −1.2 V over In2O3/rGO hybrid catalyst are 1.4 times and 3.6 times higher than those over In2O3/rGO catalyst, respectively. The insight into the great improvement in intrinsic activity was revealed by a combination of experimental evidence and DFT calculations, showing that the chemical coupling interaction accounted for the boosted CO2 electroreduction activity by improving electrical conductivity and stabilizing key intermediate HCOO−*. We believe the present work not only clearly uncovers the chemical coupling effect but also provides an effective knob to maximize the catalytic activity toward electroreduction of CO2.

■

■

Experimental details, TEM images of In(OH)3, In2O3, and In2O3/rGO, XRD patterns of In2O3, In2O3/rGO, and In2O3−rGO, Raman spectra, AFM image, XPS spectra, LSV curves, 1H NMR spectra, CVs, electrochemical impedance spectra, DFT models, work function (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (W.Z.). *E-mail: [email protected] (H.H.). *E-mail: [email protected] (J.Z.). ORCID

Wenhua Zhang: 0000-0002-0075-385X Hongwen Huang: 0000-0003-3967-6182 Chao Ma: 0000-0001-8599-9340 Jie Zeng: 0000-0002-8812-0298 Author Contributions ∥

Z.Z., F.A., and W.Z. contributed equally.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by NSFC (21603208, 21573206, 21473167), Key Research Program of Frontier Sciences of the CAS (QYZDB-SSW-SLH017), Anhui Provincial Key Scientific and Technological Project (1704a0902013), Major Program of Development Foundation of Hefei Center for Physical Science and Technology (2017FXZY002), the National Key Research and Development Program (2016YFA0200600, 2018YFA0208600), and Fundamental Research Funds for the Central Universities. This work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.

■

REFERENCES

(1) Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. R.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I. Science 2011, 334, 643− 644. (2) Chen, Y.; Kanan, M. W. J. Am. Chem. Soc. 2012, 134, 1986− 1989. (3) Ma, S.; Sadakiyo, M.; Heima, M.; Luo, R.; Haasch, R. T.; Gold, J. I.; Yamauchi, M.; Kenis, P. J. A. J. Am. Chem. Soc. 2017, 139, 47−50. (4) Bai, X.; Chen, W.; Zhao, C.; Li, S.; Song, Y.; Ge, R.; Wei, W.; Sun, Y. Angew. Chem. 2017, 129, 12387−12391. (5) Li, F.; Chen, L.; Konwles, G. P.; MacFarlance, D. R.; Zhang, J. Angew. Chem. 2017, 129, 520−524. (6) Mistry, H.; Varela, A. S.; Bonifacio, C. S.; Zegkinoglou, I.; Sinev, I.; Choi, Y.-W.; Kisslinger, K.; Stach, E. A.; Yang, J. C.; Strasser, P.; Cuenya, B. R. Nat. Commun. 2016, 7, 12123. (7) Clark, E. L.; Hahn, C.; Jaramillo, T. F.; Bell, A. T. J. Am. Chem. Soc. 2017, 139, 15848−15857. (8) Schreier, M.; Curvat, L.; Giordano, F.; Steier, L.; Abate, A.; Zakeeruddin, S. M.; Luo, J.; Mayer, M. T.; Grätzel, M. Nat. Commun. 2015, 6, 7326. (9) Liu, C.; Colón, B. C.; Ziesack, M.; Silver, P. A.; Nocera, D. G. Science 2016, 352, 1210−1213. (10) Gao, D.; Zhou, H.; Wang, J.; Miao, S.; Yang, F.; Wang, G.; Wang, J.; Bao, X. J. Am. Chem. Soc. 2015, 137, 4288−4291. (11) Zhang, S.; Kang, P.; Meyer, T. J. J. Am. Chem. Soc. 2014, 136, 1734−1737. (12) Huang, H.; Jia, H.; Liu, Z.; Gao, P.; Zhao, J.; Luo, Z.; Yang, J.; Zeng, J. Angew. Chem. 2017, 129, 3648−3652.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.nanolett.9b01393. 4033

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034

Letter

Nano Letters (13) Sun, X.; Zhu, Q.; Kang, X.; Liu, H.; Qian, Q.; Zhang, Z.; Han, B. Angew. Chem., Int. Ed. 2016, 55, 6771−6775. (14) Liu, M.; Pang, Y.; Zhang, B.; Luna, P. D.; Voznyy, O.; Xu, J.; Zheng, X.; Dinh, C. T.; Fan, F.; Cao, C.; Arquer, F. P. G.; Safaei, T. S.; Mepham, A.; Klinkova, A.; Kumacheva, E.; Filleter, T.; Sinton, D.; Kelley, S. O.; Sargent, E. H. Nature 2016, 537, 382−386. (15) Huang, H.; Li, K.; Chen, Z.; Luo, L.; Gu, Y.; Zhang, D.; Ma, C.; Si, R.; Yang, J.; Peng, Z.; Zeng, J. J. Am. Chem. Soc. 2017, 139, 8152− 8159. (16) Hu, X.-M.; Rønne, M. H.; Pedersen, S. U.; Skrydstrup, T.; Daasbjerg, K. Angew. Chem., Int. Ed. 2017, 56, 6468−6472. (17) Gao, S.; Sun, Z.; Liu, W.; Jiao, X.; Zu, X.; Hu, Q.; Sun, Y.; Yao, T.; Zhang, W.; Wei, S.; Xie, Y. Nat. Commun. 2017, 8, 14503. (18) Sekar, P.; Calvillo, L.; Tubaro, C.; Baron, M.; Pokle, A.; Carraro, F.; Martucci, A.; Agnoli, S. ACS Catal. 2017, 7, 7695−7703. (19) Zhang, C.; Hwang, S. Y.; Trout, A.; Peng, Z. J. Am. Chem. Soc. 2014, 136, 7805−7808. (20) Liang, Y.; Li, Y.; Wang, H.; Zhou, J.; Wang, J.; Regier, T.; Dai, H. Nat. Mater. 2011, 10, 780−786. (21) Feng, J.-X.; Tong, S.-Y.; Tong, Y.-X.; Li, G.-R. J. Am. Chem. Soc. 2018, 140, 5118−5126. (22) Feng, K.; Zhong, J.; Zhao, B.; Zhang, H.; Xu, L.; Sun, X.; Lee, S. T. Angew. Chem., Int. Ed. 2016, 55, 11950−11954. (23) Li, J.-S.; Wang, Y.; Liu, C.-H.; Li, S.-L.; Wang, Y.-G.; Dong, L.Z.; Dai, Z.-H.; Li, Y.-F.; Lan, Y.-Q. Nat. Commun. 2016, 7, 11204. (24) Shanmugasundaram, A.; Ramireddy, B.; Basak, P.; Manorama, S. V.; Srinath, S. J. Phys. Chem. C 2014, 118, 6909−6921. (25) Hori, Y. Mod. Aspects Electrochem. 2008, 42, 89−18.

4034

DOI: 10.1021/acs.nanolett.9b01393 Nano Lett. 2019, 19, 4029−4034