Electrochemically treated AlCoCrFeNi high entropy alloy as a self-supporting electrode for overall water splitting

The research into affordable and highly efficient overall water splitting electrocatalytic electrodes represents a crucial strategy for decentralised power generation. This study employed a two-step electrochemical method consisting of dealloying and anodic oxidation to construct microwave sintered AlCoCrFeNi high entropy alloy self-supporting efficient overall water splitting electrode. The AlCoCrFeNi high entropy alloy is mainly composed of BCC and FCC phases. After electrochemical treatment, a porous structure is formed on the surface of the AlCoCrFeNi high entropy alloy with in situ growth of ice-crystalline and lamellar structures predominantly composed of M-OOH. These structures enhance the surface wettability of the electrode and accelerate the bubble desorption during the water splitting process. After electrochemical dealloying and anodic oxidation, the overpotential of AlCoCrFeNi electrode for OER (HER) at 100 mA cm−2 significantly decreases from 366 (238) mV to 279 (173) mV, and the Tafel slope is considerably reduced to 39.73 (97) mV dec−1. Ultimately only a potential of 1.74 V is required to achieve overall water splitting at 100 mA cm−2. Excellent electrocatalytic performance of the electrode is attributed to abundant porous structure and the abundance of active sites provided by the M-OOH. Both of chronopotentiometry and continuous CV results show that the electrode has excellent electrocatalytic stability of OER, HER, and overall water splitting. This suggests that structural adjustments and surface modifications of bulk electrodes through multistep electrochemical treatment offer a new avenue for the development of overall water splitting electrodes.