Interface and M³⁺/M²⁺ Valence Dual-Engineering on Nickel Cobalt Sulfoselenide/Black Phosphorus Heterostructure for Efficient Water Splitting Electrocatalysis

The catalyst innovation that aims at noble-metal-free substitutes is one key aspect for future sustainable hydrogen energy deployment. In this paper, a nickel cobalt sulfoselenide/black phosphorus heterostructure (NiCoSe|S/BP) was fabricated to realize the highly active and durable water electrolysis through interface and valence dual-engineering. The NiCoSe|S/BP nanostructure was constructed by in-situ growing NiCo hydroxide nanosheet arrays on few-layer BP and subsequently one-step sulfoselenization by SeS₂. Besides the conductive merit of BP substrate, holes in p-type BP are capable of oxidizing the Co²⁺ to high-valence and electron-accepting Co³⁺, benefiting the oxygen evolution reaction (OER). Meanwhile, Ni³⁺/Ni²⁺ ratio in the heterostructure is reduced to maintain the electrical neutrality, which corresponds to the increased electron-donating character for boosting hydrogen evolution reaction (HER). As for HER and OER, the heterostructured NiCoSe|S/BP electrocatalyst exhibits small overpotentials of 172 and 285 mV at 10 mA cm⁻² (η₁₀) in alkaline media, respectively. And overall water splitting has been achieved at a low cell potential of 1.67 V at η₁₀ with high stability. Molecular sensing and density functional theory (DFT) calculations are further proposed for understanding the rate-determine steps and enhanced catalytic mechanism. The investigation presents a deep-seated perception for the electrocatalytic performance enhancement of BP-based heterostructure.