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, H-2 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.