2023 Fiscal Year Annual Research Report
Oxygen reduction reaction (ORR) in fuel cells on carbon-based metal-free electrocatalysts by first-principles multiscale simulations.
| Project/Area Number |
22KJ2131
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| Allocation Type | Multi-year Fund |
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| Research Institution | Osaka University |
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Principal Investigator |
WANG YUELIN 大阪大学, 工学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2023-03-08 – 2024-03-31
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| Keywords | DFT / AIMD / ORR / water/solid interfae / solvation energy |
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| Outline of Annual Research Achievements |
In this work, I use DFT calculations and AIMD simulations to investigate the ORR mechanism on sp-N1GDY/G and Pyri-NGDY/G. I got the following key points:
1. Under both vacuum and water conditions, ORR firstly proceeds on sp-N1GDY/G via the dissociative mechanism because O2 can be chemisorbed on a clean surface and easily dissociated rather than protonated to OOH*. However, OH* is strongly adsorbed on the sp-N1GDY/G surface, resulting in the weakening of the second O2 adsorption, and ORR takes place via the ET-OHP associative mechanism. Pyri-NGDY/G also prefers the ET-OHP associative mechanism.
2. From AIMD simulation, the H bond networks at the contact region of water and NGDY are mainly composed of six-membered rings H bond networks. H bond with water stabilizes each ORR intermediate and the free energy diagram with solvation effect agrees well with experimental data. Moreover, we found that using the ice-like bilayer model to construct the H bond networks can also give a reasonable estimation of ΔSol. Therefore, the ΔSol of these surfaces is independent of the water model, which arises from similar H bonds between adsorbates and water in the ice-like bilayer and AIMD H bond networks.
3. The sp-N1GDY/G with OH* pre-adsorbed surface has the highest ORR electrocatalytic activity and the neighboring C site of -COH-N moiety is the active site for ORR. Incorporation of solvation effect is of importance because η with solvation effect (0.46 V) is much closer to the experimental one (0.36 V).
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