RESUMEN
Harvesting solar energy directly to boost the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on an air cathode is a promising approach. Herein, we synthesize a step-scheme (S-scheme) titanium dioxide-indium selenide (TiO2-In2Se3) heterojunction catalyst. The onset potential in ORR under light illumination reaches 1.28 V and the onset potential decreases to 0.48 V in OER. When an S-scheme TiO2-In2Se3 heterojunction is exposed to light, photogenerated electrons at the conduction band (CB) of TiO2 migrate to the valence band (VB) of In2Se3 due to the built-in electric field. The photogenerated electrons with strong reduction capability on the CB of In2Se3 and the holes with strong oxidation capability on the VB of TiO2 boost the cathode reaction kinetics (ORR/OER). The excellent outcome reveals tremendous commercial potential of photo-enhanced Zn-air batteries.
RESUMEN
The excellent photoresponse of semiconductors enables them to be promising photocatalysts for CO2 reduction, but practical application is hampered by fast recombination of photogenerated carriers, low CO2 capture capacity and poor stability. Herein, mesoporous hollow nanospheres of a dual S-scheme titanium dioxide@indium selenide@silver phosphate (TiO2@In2Se3@Ag3PO4) heterojunction with a large specific surface area are designed and synthesized. The products of photocatalytic CO2 reduction are CH4, CH3OH and CO with yields of 3.98, 4.32 and 8.2 µmol g-1 h-1, respectively, and the photocatalysts exhibit excellent cycle performance. The excellent photocatalytic performance is attributed to the large specific surface area of the samples and the construction of dual S-scheme heterojunctions. The large specific surface area can provide sufficient active sites for photocatalytic activity. Simultaneously, the built-in electric field (IEF) in the dual S-scheme exposed to light can facilitate the migration of photogenerated electrons from the CB of the oxidation photocatalyst (OP) to the VB of the reduction semiconductor (RP), where they recombine with the photogenerated holes on the VB of the RP, leaving behind photogenerated carriers with high redox ability for photocatalytic activity. This work provides new insights into the mechanism and design of highly efficient heterojunction photocatalysts for CO2 reduction.