Electrochemical Reactive Carbon Capture: What Has Been Achieved and What Remains to Be Explored

Abstract

Electrochemical reactive carbon capture (RCC) integrates CO2 separation and conversion within a single process, offering a potential reduction in energy and process complexity compared to the conventional sequential CO2 reduction reaction (CO2RR). Here, we provided a comprehensive analysis of RCC spanning energetics, mechanistic understanding, electrochemical benchmarking, and unanswered key questions for advancement. While in principle RCC can reduce energy consumption by up to ~40% relative to sequential CO2RR by bypassing desorption and compression, experimental systems currently deliver smaller gains due to higher cell voltages and lower partial current densities. Benchmarking over one hundred studies revealed that in similar voltage ranges, RCC typically achieves partial current densities of ~200 mA/cm2, well below >1,000 mA/cm2 in gas-fed sequential electrolyzers. Among capture media, (bi)carbonate-based systems outperform carbamate systems in both partial current density and cell voltage in ambient temperature and pressure, likely due to their easier release of in situ CO2 (i-CO2) upon protonation and absence of large ammonium cations increasing the electrical double layer thickness. Techno-economic analyses confirmed that RCC is near cost parity with sequential systems for CO and ethylene (C2H4), whereas liquid products remain unfeasible due to the energy-intensive downstream liquid-phase product separation. To advance RCC, we identified three research domains that remain to be explored. First, RCC studies have largely overlooked the system-level (i.e., holistic) perspective, with alkalinity regeneration often neglected while most efforts focused narrowly on CO2RR metrics. We demonstrated that this concept heavily depends on CO2RR product type and the single-pass conversion ratio, which has been a central metric in sequential CO2RR research. Second, achieving high partial current densities remains challenging due to (i) limited i-CO2 transport to catalyst interface and (ii) exhaustion of the already limited i-CO2 by the generated hydroxides from CO2RR and parasitic hydrogen evolution. To resolve these two issues, we proposed control of microenvironment, e.g. optimizing the hierarchial porosity or utilizing redox-active neucleophile coatings, guided by multi-scale modeling as the key research priority. Finally, long-term stability, across catalyst and device scales, has not been comprehensively studied. We highlighted the necessity of descriptors for catalyst stability and prolonged experiments for improvement of device stability.