Radical Interacting Mechanisms of Photocatalytic CO2 Reduction Combined with CH3OH Reforming
The increasing concentration of atmospheric CO2 due to human activities has become a major global concern, contributing significantly to climate change. While photocatalytic reduction of CO2 offers a promising strategy for converting this greenhouse gas into valueadded chemicals using renewable solar energy, significant challenges remain in terms of efficiency and selectivity. The competition from photocatalytic H2 evolution and the low efficiency of oxidative counter reactions are key limitations that need to be addressed.
Our work presents a novel approach to selective C2 production through concurrent photocatalytic reactions of reductive CO2 conversion and oxidative CH3OH reforming. The key points of our work are summarized below:
(1) Strategic System Design: We demonstrate an active potassium poly(heptazine imide) (K-PHI) photocatalyst decorated with Pt as a co-catalyst in an alkaline aqueous system, enabling effective interaction between CO2 and CH3OH as electron acceptor and donor respectively.
(2) Exceptional Selectivity Achievement: Our system achieved a remarkable 95% selectivity for acetate (CH3COO⁻) production in the liquid phase when the CH3OH:CO2 feedstock ratio was close to 2:1, with acetate exclusively produced from the combination of CH3OH and CO2. When the CH3OH:CO2 ratio became higher (at a fixed CO2 feed), the CO2 conversion increased and the contribution of CH3COO− production from CO2 coupling also increased.
(3) Mechanistic Insights: Through comprehensive analysis of intermediates and radical species, we unraveled the complete reaction mechanism and pathways involved in this photocatalysis system, demonstrating how charge accumulation control in the photocatalyst can effectively modulate product selectivity.
This work provides valuable insights into achieving selective C2 production through photocatalytic CO2 reduction and CH3OH reforming, offering an advantageous pathway toward net-zero emission goals.