Sunlight‐Driven Overall Water Splitting by the Combination of Surface‐Modified La5Ti2Cu0.9Ag0.1S5O7 and BaTaO2N Photoelectrodes

A photoelectrochemical (PEC) cell composed of an Al-doped La5Ti2Cu0.9Ag0.1S5O7 (Al-LTCA) photocathode and a BaTaO2N (BTON) photoanode was employed for overall water splitting. The surface of the Al-LTCA photocathode was modified first with CdS by a chemical bath treatment (CBT) and subsequently with TiO2 and Pt (to form Pt/TiO2/CBT-CdS/Al-LTCA). The modified photocathode Pt/TiO2/CBT-CdS/Al-LTCA showed a significantly enhanced photocurrent for the PEC hydrogen evolution reaction in strongly alkaline aqueous phosphate solutions. This enhancement was attributed to surface stabilization by TiO2 and to the enhanced charge separation caused by the formation of a p–n junction at the CBT-CdS/Al-LTCA interface. The BTON photoanode surface modified with Co and Ir species (Ir/Co/BTON) showed a lower onset potential than that of a Co-loaded BTON photoanode for the PEC oxygen evolution reaction. A PEC cell incorporating the Pt/TiO2/CBT-CdS/Al-LTCA photocathode and the Ir/Co/BTON photoanode exhibited stoichiometric H2 and O2 generation. The solar-to-hydrogen energy conversion efficiency of this PEC cell was found to be 0.14 % following a minute of simulated sunlight irradiation.