Effects of Fe on electrocatalytic oxygen evolution reaction activity for CoFe layered double hydroxide nanosheets

Develop efficient earth-abundant electrocatalysts for water oxidation is of great importance to construct sustainable hydrogen energy system. The dual metal CoFe layered double hydroxides (LDHs) have been regarded as one kind of most promising oxygen evolution reaction (OER) catalysts due to their excellent catalytic performance. However, fundamental understanding of the effect of Fe on OER performance of CoFe-LDHs is still unclear. In this work, we report a series of CoxFey-LDHs nanosheets with different doping amount of Fe ranging from 5% to 20% (molar ratio). We systematically characterize structure and morphology of obtained CoxFey-LDHs nanosheets. Electrochemical results demonstrate that the introduction of Fe can significantly improve catalytic activity of these CoxFey-LDHs for OER with a negative shift of> 70 mV compared to pure Co(OH)2. Furthermore, optimized Co0.85Fe0.15-LDHs exhibits high intrinsic activity compared to other CoFe-LDHs nanosheets. The formation of CoIV=O species is the rate-determining step of OER for Co0.85Fe0.15-LDHs. Theoretical and experimental results indicate that CoxFey-LDHs exhibits enhanced conductivity and charge transfer compared to pure Co(OH)2. This work provides a better understanding of the effect of Fe on the OER performance of CoxFey-LDHs nanosheets.