Photo-responsive Fe single-atom dispersed FeNC-C3N4 electrocatalysts with Schottky heterojunction for photo-enhanced zinc-air batteries.

Abstract

Directly integrating solar energy into zinc-air batteries (ZABs) systems represents an eco-friendly, efficient and low-cost strategy, yet the rational design of photo-enhanced ZABs for high-performance solar energy utilization continues to pose a significant scientific challenge. Herein, the FeNC-C₃N₄ photo-electrocatalyst with Schottky heterojunction is fabricated through a facile "ball-milling and spray-coating" approach, which effectively integrates FeNC with graphitic carbon nitride (g-C₃N₄). Among them, g-C₃N₄ functions as a photoactive catalytic material, whereas FeNC serves as an efficient electroactive layer that promotes interfacial electron transfer from g-C₃N₄ under illumination, thereby improving the spatial separation of photogenerated carriers and extending their lifetime. Remarkably, in comparison with FeNC-based ZABs (370.53 mWcm^-2 and 228 h), FeNC-C₃N₄-based ZABs demonstrate a record-high power density of 540.58 mW cm^-2 under illumination, along with stable charge-discharge cycling over 1028 h at 10 mA cm^-2, representing the highest performance reported to date for photo-enhanced ZABs (PZABs). More importantly, when operated at 10 mA cm^-2 under illumination, the g-C₃N₄-modified FeNC-C₃N₄-based PZABs achieve a significantly reduced charging voltage of ∼1.94 V, in stark contrast to the conventional FeNC-based ZABs (∼2.09 V), corresponding to a notable voltage reduction of ∼0.15 V. This work offers a straightforward strategy for developing photo-enhanced ZABs that efficiently harness solar energy to reduce the charging voltage of conventional ZABs.