Assembling ultrathin Ni(OH)2 nanosheets on poly(triazine imide) crystal hollow tubes for efficient CO2 photoreduction

Abstract

Poly(triazine imide) (PTI), featuring extended conjugation and a crystallized structure, holds considerable promise for photocatalytic CO₂ reduction, yet its performance remains fundamentally constrained by inefficient charge separation and slow CO₂ activation kinetics. Herein, a one-dimensional (1D) PTI hollow tube was successfully decorated in situ with two-dimensional (2D) Ni(OH)₂ nanosheets to construct an S-scheme heterojunction for photocatalytic CO₂ reduction. The results demonstrate that the photocatalytic CO₂ conversion performance of the Ni(OH)₂@PTI composites is significantly enhanced under simulated sunlight irradiation. Specifically, the optimized Ni(OH)₂@PTI-2 sample achieves the highest CO and CH₄ yields of 20.8 and 3.1 µmol g⁻¹ h⁻¹, respectively. These yields are 2.1 and 2.0-fold higher than those of pristine PTI and represent 7.2 and 3.9-fold enhancements compared to pure Ni(OH)₂. Experimental characterization combined with theoretical simulations reveals an S-scheme charge transfer mechanism between PTI and Ni(OH)₂, which not only maintains high redox potentials but also effectively promotes the separation of photogenerated carriers. Furthermore, the well-dispersed 2D Ni(OH)₂ nanosheets on the 1D PTI hollow tubes accelerate reactant mass transfer and provide abundant, stable active sites for CO₂ adsorption and activation. This study offers fresh insights into the design of highly efficient CO₂ reduction photocatalysts.