Solar Water Splitting by TiO2/CdS/Co-Pi Nanowire Array Photoanode Enhanced with Co-Pi as Hole Transfer Relay and CdS as Light Absorber

The cobalt phosphate water oxidation catalyst (Co–Pi WOC) stabilized, CdS sensitized TiO 2 nanowire arrays for nonsacrificial solar water splitting are reported. In this TiO 2 /CdS/Co–Pi photoanode, the Co–Pi WOC acts as hole transfer relay to accelerate the surface water oxidation reaction, CdS serves as light absorber for wider solar spectra harvesting, and TiO 2 matrix provides direct pathway for electron transport. This triple TiO 2 /CdS/Co–Pi hybrid photoanode exhibits much enhanced photocurrent density and negatively shifts in onset potential, resulting in 1.5 and 3.4 times improved photoconversion efficiency compared to the TiO 2 /CdS and TiO 2 photoanode, respectively. More importantly, the TiO 2 /CdS/Co–Pi shows significantly improved photoelectrochemical stability compared to the TiO 2 /CdS electrode, with ≈72% of the initial photocurrent retained after 2 h irradiation. The reason for the promoted performance is discussed in detail based on electrochemical measurements. This work provides a new paradigm for designing 1D nanoframework/light absorber/WOC photoanode to simultaneously enhance light absorption, charge separation, and transport and surface water oxidation reaction for efficient and stable solar fuel production.