Photoelectrochemical performance of a spin coated TiO(2) protected BiVO(4)-Cu(2)O thin film tandem cell for unassisted solar water splitting

A tandem cell consisting of a Mo-BiVO(4)/TiO(2)/FeOOH photoanode–Cu(2)O/TiO(2)/MoS(2) photocathode was prepared for unassisted solar water splitting. The protective TiO(2) layer was prepared by a cost-effective spin coating technique. The individual Mo-BiVO(4)/TiO(2)/FeOOH photoanode and the Cu(2)O/TiO(2)/MoS(2) photocathode yielded a current density of ∼0.81 mA cm(−2) at 1.23 V vs. RHE and ∼−1.88 mA cm(−2) at 0 V vs. RHE, respectively under 100 mW cm(−2) xenon lamp illumination. From the individual photoelectrochemical analysis, we identify the operating points of the tandem cell as 0.66 V vs. RHE and 0.124 mA cm(−2). The positive current density from the operating points proves the possibility of non-zero operation of the tandem cell. Finally, a two-electrode Mo-BiVO(4)/TiO(2)/FeOOH-Cu(2)O/TiO(2)/MoS(2) tandem cell was constructed and analysed for unassisted operation. The obtained unassisted current density of the tandem cell was ∼65.3 μA cm(−2) with better stability compared to the bare BiVO(4)-Cu(2)O tandem cell. The results prove that the spin coated TiO(2) protective layer can be a viable approach to protect the photoelectrodes from photocorrosion with better stability and enhanced photoelectrochemical (PEC) performance.