Oxygen evolution reaction: Bifunctional mechanism breaking the linear scaling relationship

The bifunctional mechanism for the oxygen evolution reaction (OER) involving two distinct reaction sites is studied through the computational hydrogen electrode method for a set of catalyst materials including rutile TiO2(110), anatase TiO2(101), SnO2(110), RuO2(110), IrO2(110), Ni2P(0001), and BiVO4(001). The calculations are performed both at the semilocal level and at the hybrid functional level. Moreover, anodic conditions are modeled and their effect on the OER free energy steps is evaluated. The free energies of the reaction steps indicate that for specific combinations of catalysts, the limitations due to the linear scaling relationship can be overcome, leading to smaller overpotentials for the overall OER. At the same time, a detailed analysis of the results reveals a strong dependence on the adopted functional. For both functionals, it is shown that the energy level of the highest occupied electronic state can serve as a descriptor to guide the search for the optimal catalyst acting as a hydrogen acceptor. These results support the bifunctional mechanism as a means to break the linear scaling relationship and to further reduce the overpotential of the OER.

针对一系列催化剂材料（包括金红石TiO2(110)、锐钛矿TiO2(101)、SnO2(110)、RuO2(110)、IrO2(110)、Ni2P(0001)及BiVO4(001)），本研究采用计算氢电极法（computational hydrogen electrode method），对涉及两种不同反应位点的析氧反应（oxygen evolution reaction, OER）双功能机理展开研究。计算分别在半局域近似层面与杂化泛函层面完成。此外，本研究对阳极条件进行建模，并评估其对析氧反应自由能步骤的影响。反应步骤的自由能结果表明，针对特定的催化剂组合，线性标度关系带来的限制可被突破，从而降低整体析氧反应的过电势。与此同时，对结果的详细分析显示，其与所采用的泛函存在极强的依赖性。针对两类泛函，研究均表明，最高占据电子态的能级可作为描述符，用于指导作为氢受体的最优催化剂的筛选。上述结果证实，双功能机理可用于打破线性标度关系，并进一步降低析氧反应的过电势。