Interface and valence modulation on scalable phosphorene/phosphide lamellae for efficient water electrolysis

The quest for high-efficiency and earth-abundant electrocatalysts replacing precious metals for water splitting is actively pursued for the future of hydrogen economy to wean us off the dependency on fossil fuel. Herein, a moderate catalyst is constructed via the in-situ formation of well-defined CoP nanodots on electrochemical exfoliated black phosphorus (EEBP) nanosheets for overall water splitting. The electro-exfoliation process ensures a high-yield (~85%) preparation of BP nanosheets from bulk BP, prompting the large-scale chemosynthesis of CoP/EEBP heterostructures. It is demonstrated that the Co³⁺/Co²⁺ and phosphide state ratios can be elegantly tuned in the CoP/EEBP heterostructure to modulate electron donating/accepting characteristics. As for hydrogen and oxygen evolution reaction (HER/OER), CoP/EEBP heterostructure reveals remarkable electrocatalytic capacity with ultralow overpotentials of only 118 mV and 315 mV at 10 mA cm⁻² (η₁₀) in alkaline media, respectively. Coupled with CoP/EEBP heterostructure for both anode and cathode, the overall water splitting is attested stably with voltage of 1.666 V at η₁₀, which is among the best list of BP-based water-splitting electrocatalysts. The basis of the promising electrocatalytic activity is investigated using density functional theory (DFT) calculations. The results indicate that the CoP-BP interface coupling could be able to benefit the electron-transfer and accelerate the adsorption/dissociation of water. The research provides primary comprehension for the electrocatalytic fulfilment of black phosphorus revisited through valence modulation and interface engineering.