Synergistic Activity of Co and Fe in Amorphous Cox–Fe–B Catalyst for Efficient Oxygen Evolution Reaction

with a decreased overpotential of 42 mV compared to that of Co-B. The Co2-Fe-B catalyst also exhibits a small Tafel slope of 62.6 mV/dec and good stability. The enhanced performance could be attributed to the synergistic effect of the increased population of high-oxidation-state metal-OOH species and the promoted conductivity of the catalyst. A solar-to-hydrogen energy conversion efficiency of 4.2% and a Faradaic efficiency of 97.2% can be achieved by connecting the HER and as-prepared OER electrodes to a crystalline silicon solar cell.