Interconnected nanoconfining pore networks enhance catalyst CO2 interaction in electrified reactive capture

Abstract

Abstract Systems that sequentially capture and upgrade CO2 from air to fuels/fuel-intermediates, such as syngas and ethylene, rely on an energy-intensive CO2 release process. Electrified reactive capture systems transform CO2 obtained directly from carbonate capture liquid into products. Previous reactive capture systems show a decline in Faradaic efficiencies (FE) at current densities above 200 mA/cm2. Here we show the chemical origins of this problem, finding that prior electrocatalyst designs failed to arrest, activate, and reduce in situ-generated CO2 (i-CO2) before it traversed the catalyst layer and entered the tailgas stream. We develop a templated synthesis to define pore structures and the sites of Ni single atoms, and find that carbon-nitrogen-based nanopores are effective in accumulating i-CO2 via short-range, non-electrostatic interactions between CO2 molecules and the nanochannel walls. These interactions confine and enrich i-CO2 within the pores, enhancing its binding and activation. We report as a result carbonate electrolysis at 300 mA/cm2 with FE to CO of 50% ± 3%, and with <1% CO2 in the tailgas outlet stream. This corresponds to a projected energy efficiency (EE) to 2:1 syngas of 46% at 300 mA/cm2 when H2 is added using a water electrolyzer.