From CO ₂ to C ₁ 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.