化学
电子转移
电化学
氧化还原
反作用坐标
密度泛函理论
从头算
计算化学
配体(生物化学)
物理化学
热力学
过渡金属
化学物理
催化作用
无机化学
电极
有机化学
物理
受体
生物化学
作者
Phillips Hutchison,Peter Rice,Robert E. Warburton,Simone Raugei,Sharon Hammes‐Schiffer
摘要
The systematic improvement of Fe-N-C materials for fuel cell applications has proven challenging, due in part to an incomplete atomistic understanding of the oxygen reduction reaction (ORR) under electrochemical conditions. Herein, a multilevel computational approach, which combines ab initio molecular dynamics simulations and constant potential density functional theory calculations, is used to assess proton-coupled electron transfer (PCET) processes and adsorption thermodynamics of key ORR intermediates. These calculations indicate that the potential-limiting step for ORR on Fe-N-C materials is the formation of the FeIII-OOH intermediate. They also show that an active site model with a water molecule axially ligated to the iron center throughout the catalytic cycle produces results that are consistent with the experimental measurements. In particular, reliable prediction of the ORR onset potential and the Fe(III/II) redox potential associated with the conversion of FeIII-OH to FeII and desorbed H2O requires an axial H2O co-adsorbed to the iron center. The observation of a five-coordinate rather than four-coordinate active site has significant implications for the thermodynamics and mechanism of ORR. These findings highlight the importance of solvent-substrate interactions and surface charge effects for understanding the PCET reaction mechanisms and transition-metal redox couples under realistic electrochemical conditions.
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