Interfacial engineering of Co(OH)2@CN composites: A study of p-n heterojunctions with enhanced xylose/xylan photoreforming and CO2 reduction performance

Abstract

The construction of p-n heterojunction is considered a prominent method for promoting efficient separation/migration of photoinduced carriers, thereby enhancing photocatalytic performance. Herein, a series of nanoflower spherical Co(OH)₂@CN-x p-n heterojunction photocatalysts were fabricated using a simplified one-step hydrothermal strategy. Notably, Co(OH)₂@CN-2 exhibited optimal performance, showcasing a carbon monoxide (CO) evolution rate of 46.2 μmol g⁻¹ h⁻¹ and a xylonic acid yield of 69.9 %. These values are 14.7/3.7 and 2.8/2.4 times higher than those of pristine CN and Co(OH)₂, respectively. Additionally, Co(OH)₂@CN-2 demonstrated excellent recyclability and chemical stability. Comparative experiments, coupled with ¹³CO₂-labelling testing, confirmed the carbon sources of the obtained CO (72.3 % from CO₂ reduction and 27.7 % from xylose oxidation). The charge transfer mechanism in Co(OH)₂@CN-x p-n heterojunctions was systematically elucidated using in-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations. This work presents a practical approach for constructing p-n heterojunction photocatalysts to enhance photocatalytic biomass oxidation coupled with CO₂ reduction.