Corn stalk-derived carbon quantum dots-modified g-C3N4/Ni(OH)2 composite for enhanced photocatalytic CO2 reduction

In the context of the “dual carbon” goals, the development of sustainable photocatalytic systems for carbon dioxide (CO 2 ) reduction is critical for alleviating energy scarcity while mitigating carbon emissions. Utilizing agricultural waste biomass in photocatalytic systems supports the recycling of biomass resources and mitigates the environmental issues caused by stalk burning. In this study, carbon quantum dots (CQDs) with nitrogen and phosphorus doping (NP-CQDs) were prepared by a hydrothermal approach using corn stalks as the carbon source. The NP-CQDs were then incorporated into a composite with graphitic carbon nitride (g-C 3 N 4 ) and nickel hydroxide (Ni(OH) 2 ), successfully obtaining the ternary catalyst of CN/Ni/NP-CQDs. The optimal ratio composite material of CN/Ni/NP-CQDs-4 demonstrates excellent CO 2 reduction performance, exhibiting the CO and CH 4 production rates of 14.24 and 0.73 μmol g −1  h −1 , which are 10.02 and 2.28 times that of pure g-C 3 N 4 . The CN/Ni/NP-CQDs-4 has a relatively large specific surface area, which can provide more active sites and improve the CO 2 reduction efficiency. EPR results show that the Z-scheme heterojunction formed by g-C 3 N 4 and Ni(OH) 2 can effectively suppress the recombination of photogenerated carriers. NP-CQDs serve as an electron mediator, thereby enhancing photogenerated charge transfer capability. This study successfully combines biomass corn stalk derivatives with traditional photocatalytic materials, thereby addressing the challenge of utilizing agricultural waste valorization while reducing the cost of the photocatalytic system. This study provides new insights for constructing a green and sustainable CO 2 reduction photocatalytic system.