Interface Engineering of NiMoSx@NiMnFe Prussian Blue Analogue Nanowires to Efficiently Boost Overall Seawater Splitting at High Current Densities

Abstract

Developing high-activity and robust-stability electrocatalysts for hydrogen production at high current densities from seawater remains a big challenge owing to chloride corrosion and electrochemical damage at high potentials. Herein, 3D core–shell nanowires of NiMoS_x@NiMnFe Prussian blue analogue (NiMoS_x@NiMnFe-PBA) are rationally designed and prepared, exhibiting excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities in alkaline seawater with low overpotentials of 260 and 71 mV at 10 mA cm⁻², respectively. Surprisingly, as a bifunctional electrocatalyst for overall seawater splitting, it needs a low cell voltage of 1.513 V at 10 mA cm⁻² with an ultrahigh stability of 2500 h at 500 mA cm⁻², implying potential commercial applications. Both experimental and theoretical results signify its lattice oxygen mechanism pathway for OER, where the Fe and Mn efficiently decrease energy barriers to facilitate the OER kinetics. Moreover, the formed heterostructures via interface engineering create abundant active sites and facilitate rapid kinetics, while the 3D structure provides many active sites. The NiMnFe-PBA as a protective shell prevents the core of NiMoS_x from fast anodic oxidation damage and guarantees high chloride-corrosion resistance by the repelling-chloride characteristic. Accordingly, this work sheds light on developing excellent seawater-splitting electrocatalysts at high current densities.