Abstract
This study introduces a photoreactive system that integrates the capture of dilute CO(2) streams with their catalytic conversion to synthetic natural gas (CH(4)), utilizing a Ru nanoparticle (NP)-doped TiO(2) composite loaded with linear polyethylenimine (L-PEI) and enhanced with plasmonic titanium nitride (TiN). This light-driven approach mitigates challenges that have plagued traditional thermal reactive carbon capture (RCC) methods, such as CO(2) slip and amine degradation. We demonstrate that L-PEI enables stable CO(2) capture and conversion, achieving ∼70% conversion of captured CO(2) to CH(4) across multiple reaction cycles using nonflammable forming gas (∼5% H(2)) as the reductant. In contrast, branched PEI (B-PEI)-loaded composites exhibited significant catalyst deactivation after several RCC cycles. Scanning transmission electron microscopy (STEM) imaging confirms that significant sintering of the Ru NPs occur in the B-PEI sample under RCC conditions, whereas their size remains stable in more rigid L-PEI composites. Technoeconomic analysis (TEA) estimates that CH(4) production using this system could cost less than $5/kg based on current electrocatalytic H(2) prices. These results represent one of the most promising demonstrations of amine-based RCC employing dilute CO(2) sources to date.