From CO2 to C1 Liquid Fuels: Molecular Electrochemical Production of Formic Acid and Methanol.

Transforming carbon dioxide (CO2) into formic acid (HCOOH) and methanol (CH3OH) as C1 liquid fuels is central to advancing circular carbon economies and sustainable energy applications. Both CH3OH and HCOOH possess high energy density and are easily storable and transportable. Beyond their widespread use as solvents and C1 feedstock chemicals, CH3OH can be applied in fuel cells or serve as a hydrogen precursor, making it valuable for transportation and grid-level energy storage. HCOOH similarly functions as a safe hydrogen carrier and as a fuel in formic acid fuel cells. Electrochemical CO2 reduction (eCO2R) to these C1 products represents a pivotal step in closing the anthropogenic carbon loop, enabling sustainable energy storage. Recent years have brought notable advances in catalyst development, mechanistic understanding, and system optimization. Although metal-free catalysts and conductive polymers have advanced at a fast pace, transition-metal-containing systems remain the most effective, offering superior activity, selectivity, stability, and Faradaic efficiency (FE). Particularly promising are dual-function systems that integrate CO2 capture/absorption with electroreduction, offering a promising route toward the direct valorization of industrial CO2 emissions. This minireview critically evaluates recent advances in molecular and polymer-based electrocatalytic systems, design strategies, and emerging directions for next-generation CO2-to-C1 liquid fuel conversion technologies.