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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-In2Se3heterojunction is exposed to light, photogenerated electrons at the conduction band (CB) of TiO2migrate to the valence band (VB) of In2Se3due to the built-in electric field. The photogenerated electrons with strong reduction capability on the CB of In2Se3and the holes with strong oxidation capability on the VB of TiO2boost the cathode reaction kinetics (ORR/OER). The excellent outcome reveals tremendous commercial potential of photo-enhanced Zn-air batteries.

Abstract: Photocatalytic degradation has received considerable emphasis since it shows significant possibilities in environmental pollution. In this work, ternary Z-scheme heterojunction g-C3N4/TiO2/Ti3C2photocatalysts are designed and fabricated. The Z-scheme heterojunctions formed on the surfaces of g-C3N4and TiO2dramatically modify the photocatalytic performances of the compound under illumination. Meanwhile, in this process, multilayer Ti3C2, as the transport medium of Z-scheme heterojunction, is tightly bonded to TiO2generated by hydrothermal oxidation and g-C3N4with large specific surface area, which effectively facilitates the space charge separation and depresses the charge recombination. When the addition amount of TiO2/Ti3C2is 80 mg and calcined at 450 ℃ for 4 h, g-C3N4/TiO2/Ti3C2has the greatest photocatalytic performance, and the kinetic constant for degradation methyl orange (MO) was about 3.62 times that of g-C3N4and 14.55 times that of Ti3C2, respectively. This work illustrates that g-C3N4/TiO2/Ti3C2has outstanding potential and offers novel insights for designing and synthesizing new ternary heterojunction materials. Graphical Abstract: