Capturing Visible Light in Low‐Band‐Gap C<sub>4</sub>N‐Derived Responsive Bifunctional Air Electrodes for Solar Energy Conversion and Storage
Zhengsong Fang, Yuan Li, Jing Li, Chenhao Shu, Linfeng Zhong, Shaolin Lu, Chunshao Mo, Meijia Yang, Dingshan Yu
Abstract
Abstract We report facile synthesis of low‐band‐gap mesoporous C 4 N particles and their use as responsive bifunctional oxygen catalysts for visible‐light‐sensitive (VLS) rechargeable Zn‐air battery (RZAB) and polymer‐air battery (RPAB). Compared to widely studied g‐C 3 N 4 , C 4 N shows a smaller band gap of 1.99 eV, with a larger photocurrent response, and it can function as visible‐light‐harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts, enabling effective photocoupling to tune oxygen catalysis. The C 4 N‐enabled VLS‐RZAB displays a low charge voltage of 1.35 V under visible light, which is below the theoretical RZAB voltage of 1.65 V, corresponding to a high energy efficiency of 97.78 %. Pairing a C 4 N cathode with a polymer anode also endows an VLS‐RPAB with light‐boosted charge performance. It is revealed that the ORR and OER active sites in C 4 N are separate carbon sites near pyrazine‐nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.