Amorphous high-entropy phosphoxides for efficient overall alkaline water/seawater splitting

Designing and synthesizing cost-effective bifunctional catalysts for overall alkaline water/seawater splitting is still a huge challenge for hydrogen production. Herein, Co/Ni/Fe/Mn based-amorphous high-entropy phosphoxide self-standing electrode (CNFMPO) is synthesized by the facile and fast electrodeposition method. CNFMPO exhibits excellent bifunctional electrocatalytic performances on alkaline water/seawater electrolysis. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of CNFMPO in alkaline water/seawater are as low as 43/73 and 252/282 mV to reach a current density of 10 mA cm−2, respectively. Additionally, two-electrode electrolyzers with CNFMPO||CNFMPO successfully achieve the current density of 10 mA cm−2 at low voltages of 1.54 and 1.56 V for overall alkaline water/seawater splitting, respectively. CNFMPO exhibits satisfactory long-term stability on overall alkaline water/seawater splitting for the surface reconstruction into active metal hydroxide/(oxy)hydroxide, phosphite, and phosphate. Moreover, no hypochlorite is detected during seawater electrolysis for the beneficial chlorite oxidation inhibition of the reconstructed phosphite and phosphate. The excellent catalytic performances of CNFMPO are due to the unique amorphous structure, multi-component synergistic effect, beneficial electronic structure modulation, and surface reconstruction during the catalytic reaction process. Therefore, CNFMPO has shown potential promotion to the development of the water/seawater splitting industry as a promising substituent for noble-metal electrocatalysts. This work provides new insights into the design of efficient bifunctional catalysts for overall water/seawater splitting.