Supplementary Information files for: Electronic coupling strategy to boost water oxidation efficiency based on the modelling of Trimetallic Hydroxides Ni1-x-yFexCry(OH)2: from theory to experiment

Supplementary Information files for: Electronic coupling strategy to boost water oxidation efficiency based on the modelling of Trimetallic Hydroxides Ni1-x-yFexCry(OH)2: from theory to experiment. Developing low-cost yet highly efficient earth-abundant electrocatalysts for oxygen evolution reaction (OER) is of great significance for industrial scale water splitting for clean hydrogen production, as well as for rechargeable metal-air batteries. In searching for advanced catalysts, it is equally important to fundamentally understand working mechanism and be able to rationally design and manipulate catalytic sites. Starting from density functional theory (DFT) calculations as a guidance, our theoretical model revealed that chromium substitution in nickel-iron hydroxides (Ni1-xFex(OH)2) not only accelerated the charge transfer but also regulated the adsorption energy of OER intermediates such to achieve optimal binding strength. Experimentally, chromium was doped into the laminate of Ni1- xFex(OH)2, resulting in enhanced catalytic performance for oxygen evolution reaction, which confirmed the predictions from the theoretical data. The porous and ultra-thin ternary Ni1-xyFexCry(OH)2 electrocatalysts were grown directly on a nickel foam (NF) substrate, with an optimum composition Ni0.66Fe0.27Cr0.07(OH)2/NF identified, which exhibited a superior OER performance, i.e., achieving a significant current density of 10 mA cm-2 at a low overpotential of 231 mV, a small Tafel slope (31 mV dec-1) and an excellent stability at a highly oxidative potential of 1.68 V vs RHE in alkaline electrolyte. The comprehensive study involving both theoretical and experimental results in this work provides an insightful guidance in designing efficient OER catalysts for chemical and electrical energy conversion and storage.