Free-standing nanoporous high-entropy phosphides as high-performance water splitting catalysts

The fabrication of an efficient oxygen evolution reaction (OER) catalyst is essential for the advancement of renewable energy conversion technologies, including water-splitting and metal-air batteries. In this work, we fabricate a free-standing nanoporous high-entropy sulfide electrode (np-CoNiFeAgP) through the electrochemical dealloying of a multicomponent CoNiFeAgP metallic glass precursor. It is found that the single atom-state Ag doping in the formed NiCoFe-based hydroxides results in the best OER performance, which is even better than the Mo and Cr doping. Due to the amorphous properties of the precursor alloy (without any grain boundaries), even the dealloyed through np-CoNiFeAgP exhibits a good mechanical property. When used as a free-standing electrode for water splitting, it is found that the formation of a thin nanoporous layer of similar to 1 mu m is enough for reaching the highest current density, suggesting that inside surface area of a thicker nanoporous phosphide layer cannot be used for the electrocatalysis probably due to the ultrafine nanoscale pores. Impressively, the np-CoNiFeAgP exhibits an exceptional performance in OER, achieving a current density of 100 mA cm(- 2) with a small overpotential of 283 mV. When used as bifunctional electrodes for overall water splitting, it only requires similar to 1.54 V to reach 10 mA cm(- 2), exceeding that of commercial Pt/C and IrO2 combination.