Highly Tunable Syngas Product Ratios Enabled by Novel Nanoscale Hybrid Electrolytes Designed for Combined CO₂ Capture and Electrochemical Conversion

Coupling renewable energy with the electrochemical conversion of CO₂ to chemicals and fuels has been proposed as a strategy to achieve a new circular carbon economy and help mitigate the effects of anthropogenic CO₂ emissions. Liquid-like Nanoparticle Organic Hybrid Materials (NOHMs) are composed of polymers tethered to nanoparticles and are previously explored as CO₂ capture materials and electrolyte additives. In this study, two types of aqueous NOHM-based electrolytes are prepared to explore the effect of CO₂ binding energy (i.e., chemisorption versus physisorption) on CO₂ electroreduction over a silver nanoparticle catalyst for syngas production. Poly(ethylenimine) (PEI) and Jeffamine M2070 (HPE) are ionically tethered to SiO₂ nanoparticles to form the amine-containing NOHM-I-PEI and ether-containing NOHM-I-HPE, respectively. At less negative cathode potentials, PEI and NOHM-I-PEI-based electrolytes produce CO at higher rates than 0.1 molal. KHCO₃ due to favorable catalyst-electrolyte interactions. Whereas at more negative potentials, H₂ production is favored because of the carbamate electrochemical inactivity. Conversely, HPE and NOHM-I-HPE-based electrolytes display poor CO₂ reduction performance at less negative potentials. At more negative potentials, their performance approached that of 0.1 molal. KHCO₃, highlighting how the polymer functional groups of NOHMs can be strategically selected to produce value-added products from CO₂ with highly tunable compositions.