Accelerating electron transfer for high-efficiency overall water splitting via built-in electric field in Ni2P/CoP2 heterojunction nanoarray

Constructing an heterostructure electrocatalyst is a promising strategy to enhance overall water splitting performance. A nanoarray-like Ni 2 P/CoP 2 heterostructure electrocatalyst is developed, featuring a built-in electric field directed from Ni 2 P to CoP 2 , driven by the work function difference. The formation of built-in electric field facilitates charge redistribution, leading to the electron-rich and electron-deficient regions to synergistically enhance hydrogen evolution reaction and oxygen evolution reaction. In 1.0 M KOH, the Ni 2 P/CoP 2 heterostructure electrocatalyst requires a low overpotential of 68 mV for HER and 215 mV for OER at a current density of 10 mA cm −2 , outperforming most reported phosphide-based electrocatalysts. An electrolyzer utilizing Ni 2 P/CoP 2 serving as both cathode and anode electrocatalysts delivers a reduced voltage of 1.535 V at 10 mA cm −2 , which is slightly lower than that of the commercial Pt/C||RuO 2 (1.562 V). This study provides valuable insights into the design of robust bifunctional electrocatalysts for alkaline overall water splitting.