Cu-NPs embedded 1D/2D CNTs/pCN heterojunction composite towards enhanced and continuous photocatalytic CO2 reduction to fuels

Abstract

Well-designed 1D/2D composite, consisting of carbon nanotubes modified protonated carbon nitrides (CNTs/pCN) embedded with Cu-NPs were synthesized by a facile sonicated assisted chemical method. The performance of catalysts towards dynamic CO2 reduction to selective fuels was conducted under UV/visible light irradiations in a continuous flow photoreactor. Photo-activity of g-C3N4 for CO production was increased by 2.38 folds after surface charge modification due to faster charge carrier separation. Loading 3 wt% Cu and 0.5 wt% CNTs into pCN gave highest activity for the production of CO, CH4 and CH3OH under visible light. The highest CO yield as the main product over Cu-CNTs/pCN composite was 560 μmole g-cat−1 h−1, a 1.21, 1.36, 3.78 and 9.03 folds higher than using Cu/pCN, CNTs/pCN, pCN and g-C3N4 samples, respectively. This significantly enhanced photo-activity can be attributed to visible light absorption and multi-stage charges separation in the presence of Cu/CNTs. More interestingly, CO obtained under visible light was 4 times higher than using UV-light, while performance for CH4 production was 14 folds higher with visible light than using UV-light under the same operating conditions. Among the different catalyst loadings, 150 mg gave highest productivity, evidently due to limitations in exposed catalyst active surface area. Additionally, Cu-CNTs/pCN photocatalyst prevailed excellent stability in cyclic runs for continuous CO2 reduction. The findings of this work would be attractive for the development of CO2 conversion systems with renewable fuels production under solar energy.