Ha Mai-Anh, Alia Shaun M, Norman Andrew G, Miller Elisa M
Computational Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States.
Chemistry and Nanoscience Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States.
ACS Catal. 2024 Nov 11;14(23):17347-17359. doi: 10.1021/acscatal.4c04489. eCollection 2024 Dec 6.
Ni-based catalysts with Co or Fe can potentially replace precious Ir-based catalysts for the rate-limiting oxygen evolution reaction (OER) in anion-exchange membrane (AEM) electrolyzers. In this study, density functional theory (DFT) calculations provide atomic- and electronic-level resolution on how the inclusion of Co or Fe can overcome the inactivity of NiO catalysts and even enable them to surpass IrO in activating key steps to the OER. Namely, NiO resists binding the key OH* intermediate and presents a high energetic barrier to forming the O*. Co- and Fe-substitution of Ni active sites allows for the stronger binding of OH* and preferentially activates O*/O* formation, with Fe-substitution increasing the OER activity substantially as compared to Co-substitution. Whereas IrO requires an activation energy of 0.34-0.49 eV to form O, this step is spontaneous on Fe-NiO. Electrodeposition of polycrystalline electrodes and synthesized nanoparticles exploit the Co or Fe presence, with Fe particularly exhibiting greater activity: Tafel slopes indicate a significant change in the mechanism as compared to pure NiO, validating the theoretical predictions of OER activation at different steps. High-performing synthesized nanoparticles of 25% Fe-Ni exhibited a 4.6 times improvement over IrO and a 34% improvement over RuO, showcasing that non-platinum group metal catalysts can outperform platinum group metals. High-resolution transmission electron microscopy further highlights the advantages of Fe-Ni oxide synthesized nanoparticles over commercial catalysts: small, randomly oriented nanoparticles expose greater edge sites than large nanoparticles typical of commercially available materials.
含钴或铁的镍基催化剂有潜力替代珍贵的铱基催化剂，用于阴离子交换膜（AEM）电解槽中限速析氧反应（OER）。在本研究中，密度泛函理论（DFT）计算从原子和电子层面解析了钴或铁的加入如何克服NiO催化剂的惰性，甚至使其在OER关键步骤的活化方面超越IrO。具体而言，NiO难以结合关键的OH中间体，形成O存在高能垒。镍活性位点的钴和铁取代使得OH的结合更强，并优先活化O/O*的形成，与钴取代相比，铁取代使OER活性大幅提高。IrO形成O需要0.34 - 0.49 eV的活化能，而在Fe - NiO上这一步是自发的。多晶电极和合成纳米颗粒的电沉积利用了钴或铁的存在，铁尤其表现出更高的活性：塔菲尔斜率表明与纯NiO相比机理有显著变化，验证了不同步骤OER活化的理论预测。25% Fe - Ni的高性能合成纳米颗粒比IrO性能提高了4.6倍，比RuO提高了34%，表明非铂族金属催化剂可以超越铂族金属。高分辨率透射电子显微镜进一步突出了合成的Fe - Ni氧化物纳米颗粒相对于商业催化剂的优势：小的、随机取向的纳米颗粒比市售材料典型的大纳米颗粒暴露更多的边缘位点。
