Mutual promotion of CoP/CNT/Ni2P by heterojunction structural design and intrinsic activity coupling for water splitting

The design of highly stable and active bifunctional catalysts for electrolytic water remains a significant challenge. In this study, self-supported CoP/CNT/Ni2P bifunctional catalysts with three-phase heterojunction nano- structures were constructed by a multi-step electrodeposition and phosphorylation strategy. X-ray diffraction analysis and transmission electron microscope showed that CoP/CNT/Ni2P was a three-phase heterojunction nanostructure, and scanning electron microscope results of CoP/CNT/Ni2P suggested the successful introduction of carbon nanotube (CNT). The X-ray photoelectron spectroscopy results indicate a shift in the elemental binding energy in CoP/CNT/Ni2P, which is believed to contribute to the electrocatalytic reaction. The incorporation of CNT enhances charge transfer within the multiphase catalyst and maximizes the exposure of catalytically active sites, achieving an increase in catalyst performance. As anticipated, the CoP/CNT/Ni2P catalyst displays high catalytic activity for both the hydrogen evolution reaction (61 mV at 10 mA cm_ 2 ) and the oxygen evolution reaction (342 mV at 100 mA cm_ 2 ), in addition to exhibiting long-term stability at a current density of 10 mA cm_ 2 over 40 h. The electrolyzer comprising CoP/CNT/Ni2P(+,_) necessitates a modest operating voltage of 1.52 V to attain 10 mA cm_ 2 during alkaline water splitting, thereby outperforming the commercial catalyst Pt/C|| IrO2 and earlier reports. This study provides guidance for the development of ultra-high activity and durability catalysts for water splitting.