Efficient NiFe-based oxygen evolution electrocatalysts and origin of their distinct activity

Efficient oxygen evolution reaction (OER) electrocatalyst is essential for water electrolysis. Herein, high-performance NiFe-based layered double hydroxides (LDH), phosphide and sulfide OER pre-catalysts were fabricated and their distinct activity was unveiled. The as-prepared Ni x Fe 1−x S exhibits ultralow OER overpotential of 122 mV at 10 mA cm −2 in 1 M KOH. The alkali-electrolyzer using Ni x Fe 1−x S electrodes achieve superior performance exhibiting a voltage of 1.46 V at 10 mA cm −2 . Experimental analysis reveals that, during OER, Fe dissolution into electrolyte occurs for NiFe LDH and Ni x Fe 1−x P, which were both converted into NiOOH, well explaining their similar activity. Interestingly, Fe dissolution is significantly mitigated in Ni x Fe 1−x S, forming partially oxidized Fe 2 O 3 /FeOOH species. Theoretical calculations confirmed that Fe 2 O 3 /FeOOH is responsible for the enhanced OER energetics of Ni x Fe 1−x S. These observations provide new insights on the distinct activity of NiFe-based electrocatalysts, guiding their rational design as well.