Synergistic Activity–Stability Breakthrough in Overall Water Splitting by MXene-Supported High-Entropy Phosphide Architectures

Abstract

The development of highly efficient and stable bifunctional non-precious metal electrocatalysts is of critical importance for reducing the costs associated with hydrogen production through water electrolysis. In this work, a self-supporting electrode material is designed through an interfacial and high-entropy synergistic strategy. First, this involves loading MXene onto nickel foam to achieve interfacial modification, followed by the in situ growth of a quintuple high-entropy phosphide, resulting in the composite MX@CoNiZnFeMnP/NF. This design enables multiscale synergistic enhancement: at the atomic scale, the introduction of Mn, in synergy with high-entropy effects, optimizes the electronic structures of active sites; at the nanoscale, a highly conductive MXene network facilitates rapid charge transfer; at the micrometer scale, multi-level flower-like hierarchical architectures are developed, significantly enlarging the active surface area and improving mass transport. In 1.0 M KOH, the as-prepared catalyst exhibits excellent bifunctional performance, achieving overpotentials of just 73 mV at 10 mA cm–2 for the hydrogen evolution reaction and 210 mV at 50 mA cm–2 for the oxygen evolution reaction, along with Tafel slopes of 88 and 22 mV dec–1, respectively. When applied to overall water splitting, it reaches 10 mA cm–2 at a cell voltage of only 1.43 V and demonstrates remarkable durability over 70 h of continuous operation. This work offers new insights into the design of high-performance non-noble-metal water-splitting catalysts through multiscale synergistic engineering.