Morphology‐Engineered ZnIn ₂ S ₄ Nanoflowers on GaN Photoanodes for Efficient Solar‐Driven CO ₂ ‐to‐Syngas Conversion

Solar‐driven photocatalytic CO ₂ conversion is a promising method for tackling the energy crisis and reducing CO ₂ emissions. In this work, a GaN/ZnIn ₂ S ₄ (ZIS) heterojunction photoanode is constructed to elucidate how the ZIS morphology and the concentration used during spin‐coating influence photocatalytic CO ₂ reduction performance. The results show that the nanoflower‐like ZIS (ZIS‐NF) significantly enhances light‐harvesting capability and charge‐separation efficiency due to its high specific surface area of 218.401 m ² g ^{− 1} and its mesoporous structure. As a result, the GaN/ZIS‐NF heterojunction delivers a photocurrent density of 0.32 mA cm ^{− 2} , while the CO and H ₂ production rates increase by 2.6‐fold and 3.25‐fold, respectively, compared with bare GaN. Further optimization of the ZIS‐NF spin‐coating concentration reveals that a 1:10 ratio yields the highest photocurrent density of 0.37 mA cm ^{− 2} , with CO and H ₂ production enhanced by 5.28‐fold and 4.62‐fold, respectively, over bare GaN. This study provides meaningful guidance for designing high‐performance GaN‐based photoanodes to improve photocatalytic CO ₂ reduction efficiency.