Boosting cascade electron transfer in NiFe oxyhydroxide for overall water splitting

Nickel-iron oxyhydroxides are among the most active electrocatalysts, but their sluggish kinetic of oxygen evolution reaction (OER) limits the energy efficiency toward overall water splitting. Here, we present a "cascade electron transfer" strategy through spurring unidirectional electron transfer among different metal sites in Mn-doped FeNiOOH@FeNiP to boost OER and overall water splitting. The Mn doping induces a cascade electron transfer from Ni to Fe and then to Mn via metal-O-metal bridge, thus promoting the oxidation Ni and Fe centers, which in turn help charge transfer by increasing the covalency between metal-O bonds to optimize the bonding strength between metal and adsorbed oxygen species. Consequently, the optimal Mn-FeNiOOH@FeNiP delivers a fast OER kinetics (32.1 mV dec(-1)) along with a low overpotential of 215 mV@10 mA cm(-2). Benefiting from the synergistic effect of high conductivity, large specific surface area, and favorable OER kinetics, the catalyst only requires a low cell voltage of 1.456 V to achieve 20 mA cm(-2) for overall water splitting, superior to that of a commercial RuO2 parallel to Pt/C catalyst.