The direct electrochemical conversion of captured CO2, known as reactive capture of CO2 (RCC), remains a formidable challenge in heterogeneous catalysis. Given that amines are one of the most widely used capture agents for CO2, it would be desirable to electrochemically reduce the resultant adducts, such as carbamate, directly in RCC. However, current understanding suggests that the primary species undergoing reduction in RCC with amines is the CO2 dissociated from the sorbent. Herein, we employ ab initio molecular dynamics (AIMD) with DFT to analyze how the nature of alkali metal cations in the electrolyte affects carbamate at the Cu surface, thereby assessing the possibility of promoting RCC by cation effects. The simulations show that the carbamate's orientation with respect to the electrode is governed by the optimal distance between the carbamate and the cation, specifically how this distance aligns with the cation's hydration spheres. Moreover, the slow-growth AIMD results indicate that the CO2 dissociation barrier correlates with the orientation of carbamate at the interface. When the carbamate resides beyond the cation's first hydration sphere, it adopts a flat orientation with respect to the surface that promotes the release of CO2 from the capture agent. In contrast, when the carbamate disrupts the first hydration sphere and exhibits a strong cation-π interaction, it adopts an upright orientation that is less conducive to CO2 release. These findings reveal a nontrivial cation effect in RCC, suggesting that it should be possible to optimize RCC via the choice of the electrolyte.

Experiments and theory are combined to search for catalyst activity and stability descriptors for the direct reactive capture and conversion (RCC) of CO₂ in ammonia capture solutions using Cu, Ag, Au, Sn, and Ti electrodes. Two major phenomena emerge in RCC that are not predominant in the electrochemical CO₂ reduction (CO₂R) reaction, namely, the rapid corrosion and restructuring of the catalyst in the presence of the CO₂-ammonia adducts and the promotion of the competing hydrogen evolution reaction (HER). The prevalence of HER in RCC is correlated to the electrostatic attraction of the protonated amine to the electrode and the repulsion of the captured CO₂, using the potential of zero charge (PZC). The stability of catalysts under RCC conditions is a function of the applied potential and cannot be readily predicted using binding energy descriptors commonly used in the prediction of CO₂R activity. A direct correlation between calculated binding energies of CO₂R intermediates, atomic oxygen, hydrogen, and ammonia and the activity and stability of transition metals for RCC cannot be found, highlighting the need for descriptors beyond those known for CO₂R.

In this work, the electroreduction of carbon dioxide (CO2) to oxalate is enabled by incorporating trace metallic lead (Pb) on carbon-based supports (CBS) with polymer overlayers. These composite materials serve as an efficient electrocatalytic system for the facile conversion and storage of CO2, a pernicious atmospheric pollutant. Results from controlled potential electrolysis experiments indicate that 1) trace metallic Pb on the ppb scale is active toward the reductive coupling of CO2 to oxalate at comparable Faradaic efficiencies to bulk metallic Pb and 2) polymer encapsulation of this trace metallic Pb leads to promotion of CO2 reduction (CO2R) selectively to metal oxalates over other products such as CO. Importantly, metal oxalates are important alternative cementitious materials and precursors for other materials’ synthesis applications. The solid products undergo rigorous spectroscopic characterization, including 13CO2 labeling experiments, to ensure the metal oxalates are in fact produced from CO2R. These findings serve as a model for leveraging microenvironment effects to enhance activity and selectivity for CO2R using trace-metal catalysts for carbon utilization and storage technologies.