Enhanced photoelectrochemical activity of bi-functional photocatalytic fuel cell by a superior heterostructure SnO₂/BiOBr/MoS₂ photoanode

A dual-photoelectrode PFC system was constructed using an excellent SnO₂/BiOBr/MoS₂ as a photoanode and copper oxide/copper as a photocathode for the first time. The appropriate interfacial contact and outstanding photoelectrochemical activity of the photoanode can be attributed to SnO₂ hole-blocking layer. It is not only employed as a conductive scaffold for BiOBr/MoS₂ but also provided less tendency for charge transport loss. In addition, the by-product Bi₂S₃ acts as a sensitizer due to its broad absorption spectrum (∼800 nm) to increase light harvesting. The resulting SnO₂/BiOBr/MoS₂ photoanode yields the highest photocurrent density at all bias voltages and achieves 4.0 mA cm⁻², which is around eight times higher in comparison with bare BiOBr while it is twice as much as that of the BiOBr/MoS₂ photoanode without SnO₂ hole reflection layer. This study demonstrates that recombination is significantly inhibited by adding methylene blue (MB) as the hole scavenger, resulting in a high power output efficiency in the dual-photoelectrode PFC system. An ultrahigh power density of 0.045 mW cm⁻² and improved photodegradation efficiency to reach ∼ 91 % after 180 min. The excellent power density can therefore be assumed that the enriched strong oxidizing photoexcited holes were used to participate in directly decomposing MB.