Photoactive g-C3N4/CuZIF-67 bifunctional electrocatalyst with staggered p-n heterojunction for rechargeable Zn-air batteries

Energy level matching and structural stabilization of semiconductor electrode materials are critical for improving the efficiency and durability of bifunctional catalysts for photo-enhanced rechargeable Zn-air batteries. We developed a photoactive bifunctional air-electrocatalyst comprising n-type g-C3N4 and p-type copper-doped ZIF-67 (CuZIF-67) composite. g-C3N4/CuZIF-67 exhibits wide-range solar spectrum absorption and enhanced electron–hole pairs separation efficiency owing to synergistic effects of a suitable bandgap width, staggered p-n heterojunction band gap structure, and built-in electric field at its p-n heterojunction, leading to higher oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activities compared with single p- and n-type catalysts. It has photo-enhanced charge/discharge abilities, has a voltage gap of 0.81 V under 1-sun-illumination, and maintains stable cycling with 60% round-trip efficiency under illumination over 1000 cycles for 336 h at 2 mA cm−2. In conclusion, staggered p-n heterojunction and pyrrolic nitrogen-rich groups are important for efficient and durable photo-enhanced Zn air batteries. A photoactive bifunctional g-C3N4/CuZIF-67 electrocatalyst exhibits wide-range solar spectrum absorption, enhanced electron-hole pairs separation efficiency, and stable long-cycle-life battery-performance, owing to synergistic effects of a suitable bandgap width, staggered p-n heterojunction band gap structure, built-in electric field at its p-n heterojunction, and pyrrolic nitrogen-rich groups, leading to high and durable ORR/OER activities for photo-enhanced rechargeable Zn-air batteries. [Display omitted] •Robust photo-active bifunctional g-C3N4/CuZIF-67 electrocatalyst for ORR and OER.•Broad light absorption of cathode improves efficiency of photo-enhanced air battery.•Staggered p-n heterojunction promotes ORR and OER by preventing e-/h+ recombination.•Intact ZIF-structure with rich pyrrolic N groups ensures durability of the catalyst.