Internal Electric Field Modulated by Morphological Control of Sulfur-Deficient CuS for Boosted Selective CO₂ Photoreduction

Morphological control is generally applied as a modification strategy to promote photocatalysis via adsorption capacity enhancement. However, the intrinsic relationship between the internal electric field (IEF) intensity and morphological control is rarely researched. In this work, we found that the CO yield rate of CuS nanoflowers was 8.5 times higher than that of CuS nanoballs. The differences in photocatalytic performance were not induced by surface active sites because the surface S defect concentrations of CuS nanoballs and nanoflowers were similar, and the enhanced intrinsic built-in IEF of CuS flowers was explored as the internal cause. The theoretical calculations confirmed that IEF intensity could be efficiently strengthened due to the nanoflower structure of CuS. The improved carrier separation of CuS nanoflowers was primarily induced by the enhanced IEF, and the surface S defects capturing the dissociative electrons further intensified the carrier separation, which were determined by sufficient experiments. Moreover, the mechanism of enhanced selective CO2 photoreduction was explored and confirmed by efficient experimental strategies and theoretical calculations. This work revealed the effect of morphological control on promoting CO2 photoreduction via IEF intensity modulation, which provided a new perspective for photocatalysis.