Triggering heteroatomic interdiffusion in one-pot-oxidation synthesized NiO/CuFeO 2 heterojunction photocathodes for efficient solar hydrogen production from water splitting

Delafossite CuFeO 2 is a promising photocathode material for cost-efficiently photoelectrochemical (PEC) water splitting, but the unfavorable conductivity and fast recombination dynamics of photogenerated carriers limit its PEC activity for water reduction. Here, we developed a heterostructure photocathode consisting of the Cu-doped NiO (Cu:NiO) hole selective layer (HSL) and Ni-doped CuFeO 2 (Ni:CuFeO 2 ) active layer by simply annealing a homogeneous Cu–Fe oxalate layer grown on the Ni film deposited on the fluorine doped tin oxide (FTO) substrate. The obtained heterostructure of Cu:NiO/Ni:CuFeO 2 with enhanced charge carrier transportability and high-quality interface greatly promotes the separation of photogenerated carriers. Accordingly, the Cu:NiO/Ni:CuFeO 2 photocathode exhibits a high photocurrent density of ~ 0.9 mA·cm −2 at 0.2 V (vs. reversible hydrogen electrode, RHE), outperforming most of the reported bare CuFeO 2 photocathodes in the literature. And the photocurrent density can be further improved to 1.2 mA·cm −2 after decorating NiS x cocatalyst. Graphical abstract