Description:
This work demonstrates the in-depth mechanism of enhanced photoelectrochemical (PEC) water oxidation of Sb-doped rutile TiO 2 nanorods (NRs) photoanode coupled with oxygen vacancy defect-rich Co-doped CeO x (Co-CeO x ) oxygen evolution reaction (OER) cocatalyst. The defect-rich Co-CeO x cocatalyst modification improves the conductivity, light absorption, charge transfer efficiency, and surface photovoltage generation of the Co-CeO x /Sb-TiO 2 hybrid NRs photoanode. The Co-CeO x cocatalyst also serves as the surface passivating overlayer for the Sb-TiO 2 photoanode, which suppresses the surface states mediated recombination of electron-hole pairs in the NRs. The PEC studies further indicate that Co-CeO x cocatalyst induces remarkably large band bending at the semiconductor/electrolyte interface and shortens the carrier diffusion length and depletion layer width, facilitating the rapid separation and transportation of the photocarrierrs for the surface PEC reactions. The experimental and theoretical studies confirm that the Co-doping in CeO x cocatalyst enhances the surface oxygen vacancy defects, which provides active catalytic sites for OH − adsorption and charge transportation for enhanced OER kinetics. The density functional theory (DFT) calculations demonstrate a higher conductivity of the Co-CeO x cocatalyst, advantageous for rapid charge transfer capability during PEC reactions. The synergy between all these merits helps the optimized Co-CeO x /Sb-TiO 2 photoanode to deliver enhanced photocurrent and an ultra-low turn on potential of 0.1 V RHE under AM 1.5G solar illumination compared to the Sb-TiO 2 NRs (0.96 mA cm −2 at 1.23 V RHE and V on = 0.42 V RHE ). This work demonstrates the design of an efficient defect-rich cocatalyst modified photoanode for solar energy harvesting