Hierarchical electronic coupling engineering of bimetallic sulfide driven by CoFe bimetal MOFs anchored on MXene promotes efficient overall water splitting

Abstract

Rational design cost-effective water-splitting catalysts are essential for current energy storage and conversion. Here, we ingeniously design alloy-phase bimetallic sulfides anchored on the conductive substrate MXene, obtained by a facile topological hydrothermal sulfide method of self-template sacrifice using bimetallic MOFs. Density functional theory calculations (DFT) and related material characterization demonstrate that electron rearrangement at the atomic/orbital level and hierarchical electronic coupling between Schottky heterostructures of MXene boosts charge transfer efficiency, the asymmetric 3d electronic structure of the Co-Fe atoms optimizes the d-band center value εd of the Co8FeS8 MXene/NF. Thus, the efficient composite electrocatalyst of Co8FeS8 MXene/NF with multi-metal active sites exhibits extraordinary electrocatalytic performance with remarkably low overpotentials of 171 mV (OER) and 108 mV (HER) at 10 mA cm−2, respectively. Notably, when used in 1 M KOH electrolytic cell, Co8FeS8 MXene/NF also accelerate overall water splitting at an ultra-low cell voltage of only 1.51 V at 10 mA cm−2, far exceeding that of standard Pt-C/NF//RuO2/NF electrodes (1.59 V). This work gives an effective strategy to construct MOF-derived alloy-phase bimetallic sulfides and improve the intrinsic activity of alloy-phase bimetallic sulfides electrochemical catalysts.