Theoretical Investigations on Decomposition of HCOOH Catalyzed by

Article pubs.acs.org/JPCA

Theoretical Investigations on Decomposition of HCOOH Catalyzed by Pd7 Cluster Song Ju Li,‡ Xin Zhou,*,†,‡ and Wei Quan Tian*,†,‡ †

State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150080, People’s Republic of China ‡ Institute of Theoretical and Simulational Chemistry, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, People’s Republic of China S Supporting Information *

ABSTRACT: Density functional theory based calculations have been performed to investigate decomposition of HCOOH on a Pd7 cluster in vacuum and solution. The adsorption of HCOOH on Pd7 cluster occurs on a layer-bylayer quasi-planar conformation of Pd7 with 4 atoms on top and 3 atoms below. Possible reaction pathways for the decomposition of HCOOH adsorbed on Pd7 cluster in vacuum and solution are located and compared in terms of the reaction enengies and barriers. Formic acid prefers to decompose through dehydrogenation rather than dehydrate under the significant effect of solvent. The toxic species, CO generated on Pt surface, could not possibly appear in the catalytic decomposition of formic acid on Pd7 cluster due to high reaction barrier, thus no poisoning of catalyst would occur on Pd surface. The Pd7 cluster model rationalizes experimental observation, and the predictions are in good agreement with the ones based on the surface model.

1. INTRODUCTION In the past two decades, the increasing new power demand in portable electronic applications and the desire to decrease the negative environmental impacts have aroused a sustained and worldwide interest in direct liquid fuel cells.1−3 Among the direct liquid fuel cells, owing to the advantages in high battery voltage, high energy density, and low loss rate of the fuel, direct formic acid fuel cells (DFAFCs) have been considered as a promising alternative to H2 (PEMFC) and methanol-based fuel cells (DMFCs).4−6 A great deal of research about DFAFCs has been carried out in recent years.7−10 Pt electrode was first used in catalyzing formic acid, and its catalyzing mechanism is complicated. In the 20th century, it was first suggested that the electrocatalytic decomposition of formic acid on Pt generally goes through a dual-pathway mechanism:11−15 (1) Formic acid decomposes to CO2 without the generation of CO (direct pathway), in which COH, CHO,16 and COOH17 were assumed to be the reactive intermediates. (2) Intermediate CO is generated and is subsequently electro-oxidized to CO2 (indirect pathway). While, in the last ten years, besides these two pathways, Behm et al. proposed a formate pathway of formic acid decomposition on Pt,18−20 in which HCOOH decomposes to HCOO through O−H bond activation. Theoretical calculations also proposed different mechanisms.21−23 Neurock et al.21 studied the formic acid decomposition on Pt surface using density functional theory (DFT) based method and showed that the direct pathway involving the activation of the C−H bond followed by the rapid activation of the O−H bond was © 2012 American Chemical Society

the predominant pathway, in other words, COOH was the reactive intermediate on Pt surface. Liu et al.22 performed DFT based calculations with a continuum solvation model to simulate the decomposition of formic acid on Pt/H2O interface. They concluded that the adsorbed formic acid with the CH-down conformation was the active intermediate for CO2 production. To study the impact of the explicit water model, the mechanism of formic acid decomposition have been investigated by Gao et al.23 and was found that the minimum energy pathway (MEP) of the electrochemical decomposition of formic acid was the formate pathway. Although the decomposition mechanisms vary in experiment and theoretical predictions, it was found that the generation of CO is unavoidable in the process of HCOOH decomposition. CO can poison the Pt electrode and decreases its catalytic effect;24−26 therefore, the dehydrogenation reaction channel, which could improve the efficiency of the entire fuel cells and avoid catalyst poisoning, is highly needed. The key step controlling the decomposition pathway is to select an appropriate anode catalyst and disclose the decomposition mechanism of formic acid. Because of their good catalytic property, Pd-based catalysts are expected to exhibit better performance in the DFAFCs. The investigations by Ha et al.27 indicate that Pd-based DFAFCs have extremely high power density at room temperature, which Received: September 5, 2012 Revised: October 24, 2012 Published: October 26, 2012 11745

dx.doi.org/10.1021/jp308819j | J. Phys. Chem. A 2012, 116, 11745−11752

The Journal of Physical Chemistry A

Article

software package. No extra basis sets for C, O, and H were added for basis sets balance and consistency. Unlike Pt or Au, Pd shows negligible relativistic effects, so no special relativistic core pseudopotentials were used. Liu et al.22 and Gao et al.23 found that HCOOH oxidation behaves substantially different in solution and vacuum, implying that solvent effect is strongly correlated to the determination of reaction energy and reaction pathway. In this work, solvent effect was taken into account by means of the polarizable continuum model in the self-consistent reaction field method, which has been proven to be an effective solvent model to simulate water environment.43 Figure 1 displays the modeled pathways of the catalytic decomposition of formic acid. The reaction begins with a

also makes the Pd-based DFAFCs the best potential candidate for power sources of small portable electronic devices with high concentration of formic acid at low temperature. Since then, various Pd-based anode catalysts with good electro-catalytic properties, such as Pd nanoparticles, supported Pd catalysts, and Pd-based alloys,28−34 were explored. All of these anode catalysts show higher catalytic activity than pure Pt on the decomposition of formic acid. Moreover, the most remarkable difference using Pd-based catalysts from Pt is almost no generation of CO adsorbed onto Pd anode thus that the decomposition of formic acid can proceed in the absence of a poison intermediate.35,36 Therefore, Pd-based catalysts could be ideal candidates for the DFAFCs. The corresponding decomposition mechanism of HCOOH on Pd electrode was proposed, and it shows different decomposition pathways from Pt electrode. Miyake et al. reported a mechanism study of the formic acid electrodecomposition on Pd in acidic solutions.37 The surfaceenhanced infrared absorption spectroscopy indicated the adsorption of bridge-bonded formate, bicarbonate, and supporting anions on the electrode surface. As implied in this work, the formation of CO was slow and scarcely affected the decomposition of formic acid, and formate was a short-time reactive intermediate in formic acid decomposition. Brandt et al.38 investigated the electro-decomposition mechanism of formic acid on pure Pd(111)-electrode in sulphuric acid solutions, and no poisoning intermediates were observed during the decompostion.35 Although experiments have been performed to explore the HCOOH decomposition mechanism on Pd electrode, complicated and controversial mechanisms hinder the understanding of the process. State-of-the-art theoretical investigations elucidating the reaction mechanism are therefore highly desired. In previous calculations,22,23,39,40 decomposition mechanisms of formic acid on metal electrode were generally explored by DFT methods with periodic boundary conditions (PBC), and surface structure was selected as a model. Simulation of surface structures including hundreds of atoms is very time-consuming and might not be suitable for large-scale simulation of catalytic properties of alloys. A small and simple, while realistic, model would certainly facilitate theoretical modeling of the reaction mechanism. Taking many factors into account, for example: (1) usually no more than 4 atoms on the top level of surface participating in reaction,21 (2) PBC calculations have little effect on chemical reaction mechanisms, and (3) cluster model has surface character; Pd7 cluster is adopted as the catalyst model in this work to simplify the calculations to predict the catalytic properties of Pd electrodes. The exploration of decomposition mechanism of formic acid on Pd7 cluster will help to understand the catalytic process on Pd and Pd-based alloy electrodes.

Figure 1. Formic acid catalytic oxidation mechanisms (for clarity, the Pd7 cluster is replaced by a violet line).

weakly adsorbed intermediate of HCOOH*, where the star represents the status of adsorption. The first path is an indirect pathway in which formic acid is dehydrated to CO followed by oxidation of CO to CO2. In the second pathway, formic acid decomposes into CO2. The third pathway is the conversion of formic acid to a carbonyl hydroxy intermediate COOH*. The fourth pathway involves the conversion of formic acid to a bidentate formate intermediate HCOOB*. In the last pathway, HCOOB* produces a monodentate fromate HCOOM*. These pathways shown by solid lines will be discussed in section 3.2. The adsorption energy Eads, reaction energy ΔE, and reaction barrier Ebar are defined as follows: Eads = Etotal − Ecluster − E HCOOH

(1)

ΔE = E FS − E IS

(2)

E bar = E TS − E IS

(3)

where Etotal is the energy of HCOOH−Pd7, Ecluster is the energy of Pd7 cluster, and EHCOOH is the energy of HCOOH; EIS, EFS, and ETS are the total energies of the initial , final , and transition states, respectively.

2. THEORETICAL METHODS AND COMPUTATIONAL DETAILS In the present study, all electronic structure calculations were carried out with the Gaussian03 program.41 The optimized geometries and harmonic vibrational frequencies of all stationary points (reactants, products, and transition-states) were calculated by the B3LYP method42 (Becke’s threeparameter exchange functional with correlation functional of Lee, Yang, and Parr). SDD basis sets were used ((8s7p6d/ 6s5p3d) for Pd atom, (9s5p/4s2p) for C and O atoms, and (4s/2s) for H atom), the largest basis sets for Pd in the present

3. RESULTS AND DISCUSSION 3.1. Structures of Pd7 Cluster and HCOOH Adsorbed onto Pd7 Cluster. At the B3LYP/SDD level, the most stable structures of Pd7 cluster in vacuum and solution are shown in Figure 2. The structure of Pd7 cluster was found to have a triplet ground state in vacuum with pentagonal bipyramidal (PBP) as the most stable minimum, while it has a singlet state 11746



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Table 1. Transition State Barriers (ΔEbar), Important Bond Distances, and Reaction Energies of HCOOH Decomposition Catalyzed by the Pd7 Cluster in Vacuum reaction pathway

Ebar (eV)

HCOOH* → CO + H2O

Figure 2. Most stable structures of Pd7 cluster in (a) vacuum and (b) solution.

3.37

HCOOH* → CO2 + 2H

in solution with a capped square bipyramidal (CBP) conformation. This is similar to the case of Pt7 cluster.44 Among the various possible adsorption structures of formic acid on Pd7 cluster, the structures of HCOOH−Pd7 with the lowest energy in vacuum and in solution were located. Upon the adsorption of HCOOH, as shown in Figure 3, the Pd7

HCOOH* → COOH* + H → CO2 + 2H HCOOH* → HCOOB* + H → CO2 + 2H HCOOH* → HCOOB* + H → HCOOM* + H → CO2 + 2H

1.93

TS1

1.02

TS2

1.33

TS1

0.41

TS2

1.00

TS1

0.41

TS2 TS3

0.65 0.29

d (Å) C1− H1 C1− O2 O2− H1 C1− H1 O2− H2 C1− H1 O2− H2 O2− H2 C1− H1 O2− H2 C1− H1

1.188

ΔE (eV) −1.60

1.844 1.363 1.307

0.21

1.808 1.359

0.03

1.406 1.491

−0.43

1.784 1.491

−1.10

1.600

Table 2. Transition State Barriers (ΔEbar), Important Bond Distances, and Reaction Energies of HCOOH Decomposition Catalyzed by the Pd7 Cluster in Solution reaction pathway

Ebar (eV)

HCOOH* → CO + H2O

1.97

Figure 3. Most stable structures of Pd7−HCOOH in vacuum and solution. HCOOH* → HCOOB* + H → CO + OH + H

cluster distorts slightly and forms a layer-by-layer quasi-planar conformation with 4 atoms on top and 3 atoms below. Under both conditions, formic acid prefers to adsorb onto the Pd7 cluster via a di-σ conformation, i.e., formic acid binds to the top sites with the oxygen atoms of carbonyl and hydroxyl groups pointing to the adsorption surface. This is consistent with the predictions from Bakó et al.45 and Hartnig et al.46 The adsorption energies of the two models are −0.49 and −0.83 eV, respectively, indicating that formic acid can be feasibly adsorbed onto Pd7 cluster in vacuum and solution. The main geometric parameters of the adsorption in two environments are listed in Table S1 (Supporting Information). Various vibration modes and the corresponding frequencies of HCOOH* are listed in Table S2 (Supporting Information). The most evident change in the structure of HCOOH* is the O−H bond length, which is longer than that of an isolated HCOOH. The O−H bond of HCOOH* gets weaker partially due to charge transfer between them and bonding of O to the Pd7 cluster. The stretching vibration frequency of OH is redshifted, indicating that the OH bond is significantly affected when bonding to the Pd7 cluster. 3.2. Catalytic Decomposition Mechanism of Formic Acid on Pd7 Cluster. The reaction barriers, important bond distances, and reaction energies in the following pathways in vacuum and solution are listed in Tables 1 and 2.

HCOOH* → COOH* + H → CO2 + 2H HCOOH* → HCOOB* + H → CO2 + 2H HCOOH* → HCOOB* + H → HCOOM* + H → CO2 + 2H

TS1

0.06

TS2

3.01

TS1

0.27

TS2

0.46

TS1

0.06

TS2

0.61

TS1

0.06

TS2 TS3

0.68 0.04

d (Å) C1− H1 C1− O2 O2− H1 O2− H2 C1− H1 C1− O1 C1− H1 O2− H2 O2− H2 C1− H1 O2− H2 C1− H1

1.234

ΔE (eV) 0.27

2.634 1.440 1.329

−0.29

1.329 1.575 1.375

−2.25

1.428 1.329

−1.76

1.575 1.329

−2.01

1.600

3.2.1. Direct Decomposition Pathway Forming CO2 by Simultaneous C−H and C−O Activation. The structures of reactant, transition state, and product in vacuum are shown in Figure 4. In the direct pathway, the C−H and O−H bonds break concurrently and generate a CO2 and two H atoms. It is difficult to activate the C−H bond since it points away from the Pd surface. In order to dissociate this bond, the CH group must be bent out of the HCOOH plane,47 making the H1 atom 11747



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Figure 4. Structures of reactant, transition state, and product in the pathway of directly generating CO2.

the other H atom through bending the C−H bond out of the CO2 plane or transforming into the monodentate HCOOM*. In the former channel (Figure 6), HCOOB* can react directly to form CO2. In vacuum, the reaction is endothermic by 0.37 eV, and the reaction barrier is 1.00 eV. In solution, the reaction is endothermic by 0.03 eV, and the reaction barrier is 0.61 eV. The distance of the C1−H stretches to 1.784 and 1.575 Å in the transition state from 1.100 Å for the two models, respectively. In the latter channel (Figure 7), HCOOB* can rearrange to form a monodentate HCOOM*, which needs to break one Pd−O bond of HCOOB*. The adsorption energy of HCOOM* is −0.18 eV in vacuum and −1.27 eV in solution. The adsorption energy of HCOOB* is −0.80 and −1.79 eV under these two conditions, respectively. Thus, HCOOM* is less stable than HCOOB*. In vacuum, the reaction barrier of this process is 0.65 eV, and the reaction is endothermic with absorbing 0.62 eV energy. In solution, this process is endothermic by 0.52 eV, with a reaction barrier of 0.68 eV. HCOOM* subsequently breaks the O−H bond to form CO2. This process is exothermic by −0.92 and −0.74 eV in vacuum and solution, respectively. The corresponding reaction barrier is 0.29 and 0.04 eV. The distance of the C1−H1 bond of the two models elongates to 1.600 and 1.526 Å, respectively. 3.2.4. Indirect Decomposition Pathway Generating CO. In a nondirect pathway, the C−H and C−O (hydroxyl oxygen) bonds of formic acid break simultaneously, taking off a water and generating a CO, which is then oxidized to CO2 (Figure 8). The dehydrogenation reaction barrier in vacuum is 3.37 eV. The bond length of C1−O2 elongates from 1.339 to 1.844 Å, and the C1−H1 bond stretches from 1.093 to 1.188 Å in the transition state. In solution, the reaction barrier is 1.97 eV. The bond distance of C1−H1 elongates to 1.234 Å, and the H1−O2 distance shortens to 1.440 Å in the transition state. This reaction pathway in vacuum and solution are exothermic by −1.60 eV and endothermic by 0.27 eV, respectively. The lower reaction barrier in solution possibly comes from the fact that formic acid is feasible to be solvated and also the contribution of the polarization effect. Solvent reduces the dehydrogenation barrier of formic acid but is still not enough to promote the formation of CO. In solution, there may be another pathway through which the HCOOB* intermediate forms CO (Figure 9).49 In this process, the C−H and C−O (carbonyl O) of HCOOB* break synchronously to generate CO and hydroxyl intermediate.

point to the adsorbing surface of the cluster, which requires 0.74 and 0.29 eV in vacuum and solution, respectively; thus, solvation contributes to the decomposition of formic acid. In vacuum, the direct pathway has a relatively high reaction barrier of 1.93 eV and is an endothermic reaction (0.21 eV). The distance of the C1−H1 bond elongates from the initial value of 1.093 to 1.307 Å, while the distance of the O2−H2 extends from 1.029 to 1.808 Å. It is noteworthy that this decomposition pathway is not located in solution. No matter what the initial structure is adopted, the H atom on the hydroxyl would take off first in solution. 3.2.2. Direct Decomposition Pathway by the Formation of a Carbonyl Hydroxyl Intermediate. If the C−H bond of formic acid is activated, COOH* forms (Figure 5). Like the direct pathway forming CO2 by simultaneous C−H and C−O activation, the CH group must be bent out of the HCOOH plane. The reaction barrier of the C−H bond breaking is 1.02 eV in vacuum and 0.27 eV in solution. The C1−H1 bond stretches from 1.093 to 1.359 Å in vacuum, while to 1.375 Å in solution. The reaction barrier of breaking the O−H bond is 1.33 and 0.46 eV in the two models, respectively. In this process, the initial O2−H2 bond length is 0.982 Å in vacuum and 0.985 Å in solution. The elongation of the O2−H2 bond in the two models is 0.424 and 0.443 Å, respectively, in the transition state. In vacuum, the reaction energies of the two steps are 0.16 and 0.36 eV, while in solution, these two reaction energies are −0.26 and −1.16 eV, respectively. Accordingly, formic acid may generate the COOH* intermediate on Pd7 cluster in solution. 3.2.3. Direct Decomposition Pathway by the Formation of Formate Intermediate. The formate pathway is initiated by O−H bond breaking followed by formation of a bidentate conformation of HCOOB* as shown in Figure 6. In vacuum, this process is exothermic with reaction energy of −0.31 eV and an activation barrier of 0.41 eV. The O2−H2 bond length stretches from 1.029 to 1.419 Å in the transition state. In solution, the O−H bond activation barrier is 0.06 eV, and the reaction is exothermic by −0.96 eV. The bond distance of O2− H2 becomes 1.329 Å in the transition state. The HCOOB* bridges over the Pd cluster surface via its two oxygen atoms,48,49 where the bond length of O1−Pd6 is 2.103 Å and that of O2−Pd7 is 2.207 Å in vacuum, and 2.179 and 2.152 Å in solution, respectively. As a result, the HCOOB* can draw off 11748



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Figure 5. Structures of reactant, transition state, and product in the pathway of formation of the carbonyl hydroxyl intermediate in (a) vacuum and (b) solution.

Figure 6. Structures of reactant, transition state, and product in the direct pathway of formation of the formate intermediate in (a) vacuum and (b) solution.

The process is endothermic by 1.50 eV, with a high reaction barrier of 3.01 eV. The bond distance of C1−H1 becomes longer from 1.100 to 1.338 Å, and the C1−O1 bond stretches to 1.435 Å from 1.292 Å. 3.3. Summary of Reaction Mechanisms. The reaction mechanism of HCOOH catalyzed by a Pd7 cluster in vacuum and solution are shown in Figure 10. Figure 11 is the potential energy curve of the decomposition pathway under these two conditions. 3.3.1. Mechanism in Vacuum. The reaction barrier (in Figure 11a) of the indirect pathway to form CO is the highest

of 3.37 eV. So in vacuum, it is energetically unfavorable for formic acid to take off a molecule of H2O and directly generate CO on the Pd7 cluster, although this process is exothermic. The reaction barrier of the direct pathway for generating CO2 by concurrently taking off two H atoms is so high (1.93 eV). The two reaction barriers of forming the COOH* intermediate are 1.02 and 1.33 eV, respectively, which are lower than those in the first two reaction pathways. However, it is generally believed that a reaction is not energetically feasible if the reaction barrier is higher than 1.3 eV. The minimum energy pathway corresponds to the monodentate formate HCOOM* 11749



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Figure 8. Structures of reactant, transition state, and product in the pathway of indirect oxidation generating CO by dehydrogenation in (a) vacuum and (b) solution.

Figure 9. Structures of reactant, transition state, and product in the pathway of indirect oxidation generating CO by the HCOOB* intermediate.

Figure 7. Structures of reactant, transition state, and product in the direct pathway of generating the HCOOM* intermediate in (a) vacuum and (b) solution.

pathway in the vacuum model. The three reaction barriers in this process are very low (0.41, 0.65, and 0.29 eV), and this process is exothermic. That is, the adsorbed formic acid on Pd7 cluster prefers to be oxidized to CO2 by forming the formate intermediate in vacuum. 3.3.2. Mechanism in Solution. The process of taking off the H atom from the hydroxyl group has a very low reaction barrier in solution (0.06 eV in Figure 11b). Hence, in solution, the species absorbed on the Pd7 cluster should be HCOOB* and H atom. The reaction barrier of direct forming CO is 1.97 eV, indicating that this reaction is not feasible at room temperature in solution. The generation of CO from HCOOB* has a reaction barrier of 3.01 eV, which is much higher than the direct dehydration pathway, thus does not feasibly occur. This

Figure 10. Reaction mechanism of HCOOH catalyzed by the Pd7 cluster in vacuum and solution (reaction energy is denoted in bold and reaction barrier is denoted in italics).

is in agreement with the previous formic acid decomposition on Pt surface predicted by DFT method.22,23 The reaction barriers of forming the COOH* intermediate are 0.27 and 0.46 eV, 11750



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Figure 11. Potential energy curves of HCOOH decomposition catalyzed by the Pd7 cluster in (a) vacuum and (b) solution.

respectively. Taking off the H atom from HCOOB* requires 0.61 eV energy; nevertheless, the reaction barrier for the conversion of this structure to HCOOM* is 0.68 eV. In summary, HCOOB* intermediate could form in the decomposition of HCOOH in solution due to the feasibly activated O−H bond, as well as the large reaction energy and low activation barrier in the path of HCOOH* → HCOOB* + H → CO2 + 2H. Therefore, the MEP corresponds to the bidentate formate (HCOOB*) pathway in solution, and it is exothermic. The transformation energy from HCOOB* to HCOOM* is very small, but the reaction barrier in the HCOOM* path is higher than that of the HCOOB* path; thus, the HCOOM* path should be the secondary MEP. Another competing reaction channel is the COOH* path, though this reaction is overall exothermic, and the energy released in the first adsorption step (HCOOH → HCOOH*) is not enough to overcome the other two activation barriers. Taking into account the moderate activation barriers in this path, COOH* intermediate could form with low priority, which is consistent with the experimental observation of almost no COOH intermediate found on Pd surface.37,38

4. CONCLUSIONS The structure of Pd7 cluster and the formic acid decomposition mechanism catalyzed by Pd7 cluster in vacuum and solution have been investigated within density functional theory. For Pd7 cluster, it has a triplet ground state in vacuum with pentagonal bipyramidal as the most stable minimum, while its most stable structure in solution has a singlet state with a capped square bipyramidal conformation. Upon the adsorption of HCOOH in vacuum and solution, Pd7 cluster changes to a quasi-planar layered conformation with 4 atoms on top and 3 atoms below. The effect of solution on the reaction pathway, reaction barrier, and energy is significant. Formic acid prefers to decompose through dehydrogenation rather than dehydration, and CO2 would be the main product. The toxic species of CO generated on Pt surface by the nondirect way does not appear in the decomposition of formic acid on Pd7 cluster. The Pd7 cluster model rationalizes experimental observations, and the predictions are in good agreement with the ones based on the surface model and thus might be extendable to similar systems and catalytic reactions. 11751



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ASSOCIATED CONTENT

S Supporting Information *

Geometric parameters of free HCOOH and HCOOH* in vacuum and solution; various vibration modes and corresponding frequencies of the free HCOOH and HCOOH*. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel: 86-451-86403305. Fax: 86-451-86403305. E-mail: [email protected] (X.Z.), [email protected] (W.Q.T.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is supported by Open Project of State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (No. QA201116). W.Q.T. thanks financial support from the State Key Lab of Urban Water Resource and Environment (Harbin Institute of Technology) (2012DX02), National Key Laboratory of Materials Behaviors & Evaluation Technology in Space Environments (HIT), and the Open Project of State Key Laboratory of Supramolecular Structure and Materials (JLU) (SKLSSM201206).

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Theoretical Investigations on Decomposition of HCOOH Catalyzed by

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