Photocatalytic overall water splitting without noble-metal: Decorating CoP on Al-doped SrTiO₃

CoP, a noble-metal-free cocatalyst, was first introduced onto the surface of Al-doped SrTiO₃ (Al:STO) via an in situ photodeposition-phosphorization method for photocatalytic overall water splitting (POWS) into stoichiometric H₂ and O₂. Compared with pure Al:STO, the POWS activity was enhanced by a factor of ~ 421 over 1.0%CoP/Al:STO, with the highest evolution rates of 2106 and 1002 μmol h^-1 g^-1 for H₂ and O₂, respectively. The mechanism for the remarkably boosted POWS activity was systematically analyzed based on the comprehensive characterization. On the one hand, benefiting from the in situ photodeposition process, CoP with metallic character were intimately decorated onto the surface of Al:STO and accelerated the separation and migration of photoinduced charge carriers. On the other hand, CoP, serving as reactive sites for H₂ evolution reaction, lowered the overpotential and facilitated the surface reduction reaction, thereby enhancing the POWS activity. Furthermore, Cr₂O₃ was photodeposited on the surface of 1.0%CoP/Al:STO composite to suppress the undesired reverse reaction and the POWS activity was further enhanced up to 3558 and 1722 μmol h^-1 g^-1 for H₂ and O₂, respectively, with apparent quantum yield of 7.1% at 350 ± 10 nm. This work presents a new avenue for designing POWS system without noble-metal cocatalyst.