RESUMO
High-rate production of multicarbon chemicals via the electrochemical CO2 reduction can be achieved by efficient CO2 mass transport. A key challenge for C-C coupling in high-current-density CO2 reduction is how to promote *CO formation and dimerization. Here, we report molecularly enhanced CO2-to-*CO conversion and *CO dimerization for high-rate ethylene production. Nanoconfinement of ascorbic acid by graphene quantum dots enables immobilization and redox reversibility of ascorbic acid in heterogeneous electrocatalysts. Cu nanowire with ascorbic acid nanoconfined by graphene quantum dots (cAA-CuNW) demonstrates high-rate ethylene production with a Faradaic efficiency of 60.7% and a partial current density of 539 mA/cm2, a 2.9-fold improvement over that of pristine CuNW. Furthermore, under low CO2 ratio of 33%, cAA-CuNW still exhibits efficient ethylene production with a Faradaic efficiency of 41.8%. We find that cAA-CuNW increases *CO coverage and optimizes the *CO binding mode ensemble between atop and bridge for efficient C-C coupling. A mechanistic study reveals that ascorbic acid can facilitate *CO formation and dimerization by favorable electron and proton transfer with strong hydrogen bonding.
RESUMO
The electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) is considered a promising technology for converting atmospheric CO2 into value-added compounds by utilizing renewable energy. The CO2RR has developed in various ways over the past few decades, including product selectivity, current density, and catalytic stability. However, its commercialization is still unsuitable in terms of economic feasibility. One of the major challenges in its commercialization is the low single-pass conversion efficiency (SPCE) of CO2, which is primarily caused by the formation of carbonate (CO32-) in neutral and alkaline electrolytes. Notably, the majority of CO2RRs take place in such media, necessitating significant energy input for CO2 regeneration. Therefore, performing the CO2RR under conditions that minimize CO32- formation to suppress reactant and electrolyte ion loss is regarded an optimal strategy for practical applications. Here, we introduce the recent progress and perspectives in the electrochemical CO2RR in acidic electrolytes, which receives great attention because of the inhibition of CO32- formation. This includes the categories of nanoscale catalytic design, microscale microenvironmental effects, and bulk scale applications in electrolyzers for zero carbon loss reactions. Additionally, we offer insights into the issue of limited catalytic durability, a notable drawback under acidic conditions and propose guidelines for further development of the acidic CO2RR.
