Exploiting the synergistic catalytic effects of CoPi nanostructures on Zr-doped highly ordered TiO₂ nanotubes for efficient solar water oxidation

Photoelectrochemical (PEC) catalysis offers promising strategies for sustainable development. This study demonstrated the synergistic catalytic behavior of ZrO₂ and a cobalt phosphate on anodized TiO₂ nanotubes (TNTs), which significantly enhanced the PEC performance for visible-light-driven water splitting reactions. The sequential addition of ZrO₂/CoPi-decorated TNTs was performed via electrodeposition and photoassisted electrodeposition. The substitution of Zr⁴⁺ by Ti⁴ can lead to the creation of oxygen vacancies, enabling electron trapping, reducing charge recombination, and thereby enhancing the charge transfer efficiency. Further, in the case of TNTs/ZrO₂/CoPi photoanode, the CoPi WOC functioned as a hole-transfer relay to promote the water-splitting reaction. Specifically, incorporating ZrO₂/CoPi rushes the surface reaction kinetics of TNTs and considerably improves charge transfer efficiency (η_CT = 90%), photocurrent density (0.86 mA/cm² at 1.23 V_RHE) and durability were obtained. Further, the mechanistic examination by impedance measurements showed the enhanced charge transfer, and surface conductivity for prepared materials. The proposed method can be widely used to develop electrodes made of other materials to produce solar fuels.