Electrodeposition of Fe-Group Mutual Alloys for Efficient Electrochemical Water Oxidation

In this work, galvanostatic electrodeposition from an electrolyte without buffers was performed to generate thin films consisting of Ni, Fe and Co on various substrates. The self-limiting behavior was proven by electroplating at different durations, showing that the thickness was unchanged. The growth was self-limiting due to the pH increase, resulting in an outer layer composed of a compact hydroxide/oxyhydroxide. XPS depth profiles confirm the formation of the surface hydroxide/oxyhydroxide. Studies of nucleation dynamics show that these films nucleate slower if the alloy films include more elements. Ni-Co-Fe films deposited on Au were further investigated as electrochemical catalysts in 1M KOH solution for oxygen evolution. All the films exhibit reduced Tafel slopes (34.7 to 38.4 mV/dec) and small onset potentials (0.314 to 0.320 VRHE), implying an enhanced water oxidation kinetics. The optimum deposition time was found to be 1s in terms of the electrochemical catalytic properties, due to a lower thickness of the surface hydroxide/oxyhydroxide layer.