Triple-function Mn regulation of NiFe (oxy)hydroxide for oxygen evolution reaction

Transition metal (oxy)hydroxides are potential oxygen evolution reaction (OER) electrocatalysts; however, simultaneously modulating multiple factors to enhance their performance is a grand challenge. Here, we report an incorporating heteroatom strategy via one-step hydrothermal approach to adjust more than one factor of Mn-doped NiFe (oxy)hydroxide (Mn-NiFeOOH/LDH) heterojunction. Mn doping regulates heterojunction morphology (reducing nanoparticles and becoming thinner and denser nanosheets), Ni/Fe ratio and valence states (Ni2+, Ni3+, and Ni3+Δ) of Ni ions. The former could effectively increase surface active sites, and the latter two reduce the content of Fe in the Mnx-NiFeOOH/LDH heterojunction, enabling more Ni2+ convert to Ni3+/3+Δ that have higher intrinsic OER activity. As a result, the first-rank Mn-NiFeOOH/LDH with ultra-low overpotential of 185 mV@20 mA cm−2 and 296 mV@500 mA cm−2, and the improved OER performance are outdo to those of commercial RuO2 catalyst for OER. Moreover, the Mn-NiFeOOH/LDH affords the earliest initial potential (1.392 V vs. RHE), corresponds to a recorded low overpotential (162 mV). Based on the density functional theory (DFT), Mn dopants can alter intermediate adsorption energy and effectively decrease OOH*'s energy barrier. This research exhibits a feasible strategy to design low cost electrocatalysts and provide new possibilities for future industrialization.