Constructed Co3O4-Sn3O4 hierarchical nanoflower-tree heterostructure with boosting photoelectrocatalytic efficiency for water decontamination

• The Co 3 O 4 -Sn 3 O 4 hierarchical nanoflower-tree architecture was synthesized. • It exhibited excellent reactive brilliant blue KN-R degradation capabilities. • It showed a decomposition efficiency of 87.5% with stability of 13,000 s. • The mechanisms of the synergistic photoelectrocatalytic effect were explored. Refractory organic pollutants' degradation efficiency strongly depends on the amount of intermediate active species (hydroxyl radical and superoxide radical) in the photoelectrocatalytic (PEC) process. Here, the various amount of Sn 3 O 4 nanosheets is adhered to the surface of Co 3 O 4 nanowires by a simple hydrothermal process to assemble the Co 3 O 4 -Sn 3 O 4 hierarchical nanoflower-tree architecture. The as-obtained Co 3 O 4 -Sn 3 O 4 -2.0 (2 mmol tin salt precursor) photoelectrodes exhibited superior PEC dye degradation efficiency than bare Co 3 O 4 photoelectrode because the Co 3 O 4 -Sn 3 O 4 -2.0 hierarchical architecture has large electrochemical active, fast interfacial carrier transport, low electrochemical resistance, a proper bandgap, high electron-hole separation efficiency, and electron-deficient surface. Especially, Co 3 O 4 -Sn 3 O 4 -2.0 hierarchical architecture can promote the generation of intermediate active species (hydroxyl radical and superoxide radical) as the demonstration from the energy band structures, which play the predominant role in the PEC process. Additionally, the electron-deficient surface enhances the interaction with active species and increases stability during the PEC process. Overall, Co 3 O 4 -Sn 3 O 4 -2.0 architecture demonstrated the best PEC degradation rate (~87.5% in 2 h) and long-term stability (~13,000 s) in 0.1 mol/L Na 2 SO 4 toward the accelerated degradation of reactive brilliant blue KN-R. The present work provides a feasible and straightforward route to obtain highly efficient PEC photoanode through a rational combination of Co 3 O 4 and Sn 3 O 4 with proper energy band tuning, which will guide other heterojunction designs.