FeNi (oxy)hydroxides embedded with high-valence Mo atoms: A efficient and robust water oxidation electrocatalyst.

[Display omitted] • High-valence Mo atoms embedded in FeNi (oxy)hydroxides are realized by boronation. • MoFeNi ultrathin nanoflakes promote mass diffusion and electron transfer for OER. • Mo can modulate electronic structure and optimize intermediates adsorption energy. • AEM electrolyser produce hydrogen continuously for several hours at 500 mA cm−2. The incorporation of high-valence transition metal atoms into FeNi (oxy)hydroxides may be a promising strategy to regulate the intrinsic electronic states, thereby reducing the thermodynamic barrier and accelerating oxygen evolution reaction (OER). Here, a high-valence Mo atoms doping route is proposed by an efficient self-reconstruction strategy to prepare MoFeNi (oxy)hydroxides for efficient alkaline OER. By using borides (MoNiB) as sacrificial template and Mo source, FeNi (oxy)hydroxides nanoflakes embedded with high-valence Mo atoms (MoFeNi) is successfully synthesized, which can modulate the electron coordination to improve the intrinsic catalytic activity. Remarkably, the obtained MoFeNi exhibits extremely low overpotential (η 100 = 252 mV and η 500 = 288 mV) and small Tafel slope (18.35 mV dec-1). The robust catalyst can run stably for hours at 500 mA cm−2. Characterization results and theoretical calculations confirmed that the addition of high-valence Mo effectively modulated the intrinsic electronic structure of metal sites and optimized the adsorption/desorption energy of the intermediates, accelerating OER reactions kinetics. By coupling MoFeNi anode with Pt/C cathode, anion exchange membrane (AEM) electrolyser can operate stably at 500 mA cm−2 with about less than 2.2 V. This research introduces a novel approach to develop ideal electrocatalysts through the incorporation of high-valence molybdenum species. [ABSTRACT FROM AUTHOR]