One-step preparation of cobalt phosphate at room temperature for effective photocatalytic H₂ evolution

Cobalt phosphate materials were prepared in the present work in one step at room temperature using different raw materials and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N₂ gas adsorption. Cobalt phosphates exhibit 3D flower-like structures, and the assembly of nanosheets (petals of the "flowers") of cobalt phosphate prepared with sodium phosphate and cobalt acetate as raw materials (denoted as Co-P(A)) is more incompact than that of cobalt phosphate prepared with diammonium hydrogen phosphate and cobalt nitrate as raw materials (denoted as Co-P(B)) due to the former's mildly basic environment. The cobalt phosphates show relatively high photocatalytic activity for H₂ evolution reaction (HER) in the presence of Eosin Y as a sensitizer in an aqueous triethanolamine solution. The activity of Co-P(A) (0.40 mmol h^-1 g^-1) exceeds that of Co-P(B) (0.19 mmol h^-1 g^-1), which can be attributed to a more dispersive nanosheet and larger BET-specific surface area of Co-P(A). The mechanisms of photocatalytic HER and the formation of flower-like Co₃(PO₄)₂ were discussed. The present system comprising of only abundant elements contributes toward the development of cost-efficient solar HER to achieve sustainable development.