Overall water splitting on surface-polarized Sn3O4 through weakening the trap of Sn(II) to holes

As an ideal candidate for photocatalytic overall water splitting, Sn3O4 only be active with the help of hole sacrificial agent. In this work, we reveal the corresponding mechanism and provide a feasible strategy based on surface polarization. The results show that the Sn(II) in Sn3O4 would trap the holes and then be oxidized during water splitting, leading to photocorrosion and weak oxygen evolution activity. The phosphoric acid modification could enhance the activity of Sn3O4 for oxygen evolution, and overall water splitting is achieved accordingly. The hydrogen and oxygen evolution rates can reach up to 9.6 and 4.5 nmol g(-1) h(-1), respectively. It is mainly due to the modified phosphate groups could make Sn3O4 carry more negative charges by ionization in water. The generated surface electric field could weaken the trapping effect, thus the holes can arrive at the surface effectively, along with improved stability and charge carrier separation.