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

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.