Integration of LaCo(OH)_x Photo-Electrocatalyst and Plasmonic Gold Nanoparticles with Sb-Doped TiO₂ Nanorods for Photoelectrochemical Water Oxidation

This work demonstrates a strategic nanoengineering design of a TiO2 nanorod (NR)-based photoanode. Here, the doping of Sb in TiO2 NRs along with co-integration of plasmonic gold nanoparticles and an amorphous lanthanum-cobalt double hydroxide (LaCo(OH)x) oxygen evolution catalyst (OEC) is found to improve visible-light absorption, rapid electron–hole pair separation, fast electron transportation, and the surface photocatalytic reaction of the photoanode, resulting in the ameliorated water oxidation performance. The Sb-doped TiO2 NRs exhibit a reduced band gap, improved photoconductivity, and an excellent photocurrent density (1.03 mA·cm–2 at 1.23 V vs reversible hydrogen electrode (RHE)). The anchoring of Au nanoparticles on Sb-TiO2 NRs significantly improves visible-light absorption and the photocurrent density because of the localized surface plasmon resonance effect. Herein, LaCo(OH)x is demonstrated as a photo-electrocatalyst and incorporated with a TiO2 NR-based photoanode for the first time. Integration of a suitable amount of the LaCo(OH)x OEC with Au/Sb-TiO2 NRs significantly improves photocarrier separation, photogenerated charge transportation, and the surface photo-electrocatalytic reaction and reduces the charge transfer resistance, delivering above 10 mA/cm2 photocurrent density at 2.06 V vs RHE and resulting in the enhanced photoelectrochemical (PEC) activity and photostability for water oxidation. The LaCo(OH)x-electrodeposited Au/Sb-TiO2 NR sample exhibits a hydrogen production rate of 21.4 μmol·cm–2·h–1 at the counter electrode under illumination. This work demonstrates a strategic design of a TiO2-based photoanode integrating doping with plasmonic nanostructures and cocatalysts for solar fuel production through water splitting.