Electrocatalytic urea synthesis via the co-reduction of \({{{\rm{NO}}}}_{3}^{-}\) and CO₂ as a promising option to the conventional Bosch-Meiser remains challenged by regulating desired intermediates to simultaneously achieve a high yield and Faradaic efficiency. Here, we integrate the substrate material (SiO₂) and functionally atomic sites (Cu and Sn) utilizing CeO_x nanoclusters as ‘adhesive’, in which the CeO_x and SiO₂ form the composite carrier (CS) construct Cu and Sn diatomic electrocatalyst (CuSn/CS−1). Spectroscopic techniques and density functional theory calculations reveal that overall charge redistribution in the CeO_x−CuSn modules forms bifunctional active sites with unique electronic properties and abundant oxygen vacancies. The Cu sites mediate the conversion of CO₂ to *CO through a single carbon-coordinated structure with *CO₂⁻, while Sn sites regulate the reduction of \({{{\rm{NO}}}}_{3}^{-}\) to stabilize the formation of *NH₂, broadening the C−N coupling route. Oxygen vacancies provide additional electron storage sites and promote the electron flow during the electrocatalytic process. CuSn/CS−1 achieves a urea yield of 55.81 mmol g⁻¹_cat. h⁻¹ with a Faradaic efficiency of 79.27% in H-cell at −0.7 V versus the reversible hydrogen electrode. This work overcomes the traditional trade-off between urea yield and Faradaic efficiency, providing a feasible and sustainable strategy.

Significance: The mechanisms by which abiotic, long-chain hydrocarbons are produced in natural alkaline hydrothermal systems are unknown, as only short-chain hydrocarbons (<5 carbons) have been experimentally observed to date. Here, we demonstrate how the hydrothermal reduction of bicarbonate into long-chain hydrocarbons (≤24 carbons) occurs through the use of iron and cobalt metals. In contrast to the traditional Fischer–Tropsch synthesis, in which water is the driving force for catalyst deactivation, Co exhibits unique catalytic stability in hydrothermal conditions through bicarbonate-assisted CoO _x reduction, thus promoting the carbon−carbon coupling process with the synergistic effect from the iron hydroxyl group. This finding helps to explain the abiogenic origin of petroleum, life’s emergence, and further contributes to artificial carbon dioxide utilization in the chemical industry.

Converting CO₂, a major component of greenhouse gas in the atmosphere, into value‐added fine chemicals is beneficial from environmental and economic aspects. Except for various methods for CO₂ reduction such as thermal catalysis, photocatalysis, electrocatalysis and biological reduction, hydrothermal reduction of CO₂ to organics is becoming a novel and promising strategy. The hydrogen formed in situ from high‐temperature water could avoid the serious issues of hydrogen storage and transportation. This paper summarizes the recent advances on CO₂ conversion to formic acid with metal‐ and biomass‐based compounds under hydrothermal conditions mainly focusing on the role of high‐temperature water, autocatalysis mechanism of metal reductants, and interfacial catalysis mechanism of metal/metal oxides. The effects of several experimental variables including temperature, reaction time and pH of the solution on formic acid yield are systematically illustrated as well. Finally, future efforts for fundamental researches and industrial applications of hydrothermal CO₂ reduction are discussed.