Electrochemical Upgrading of Formic Acid to Formamide via Coupling Nitrite Co-Reduction.

Formic acid (HCOOH) can be exclusively prepared through CO2 electroreduction at an industrial current density (0.5 A cm-2). However, the global annual demand for formic acid is only ∼1 million tons, far less than the current CO2 emission scale. The exploration of an economical and green approach to upgrading CO2-derived formic acid is significant. Here, we report an electrochemical process to convert formic acid and nitrite into high-valued formamide over a copper catalyst under ambient conditions, which offers the selectivity from formic acid to formamide up to 90.0%. Isotope-labeled in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and quasi in situ electron paramagnetic resonance results reveal the key C-N bond formation through coupling *CHO and *NH2 intermediates. This work offers an electrochemical strategy to upgrade CO2-derived formic acid into high-value formamide.

Electrocatalytic Reduction of CO2 to Ethanol at Close to Theoretical Potential via Engineering Abundant Electron-Donating Cuδ+ Species.

Electrochemical CO2 reduction to liquid multi-carbon alcohols provides a promising way for intermittent renewable energy reservation and greenhouse effect mitigation. Cuδ+ (0<δ<1) species on Cu-based electrocatalysts can produce ethanol, but the in situ formed Cuδ+ is insufficient and easily reduced to Cu0 . Here a Cu2 S1-x catalyst with abundant Cuδ+ (0<δ<1) species is designedly synthesized and exhibited an ultralow overpotential of 0.19 V for ethanol production. The catalyst not only delivers an outstanding ethanol selectivity of 86.9 % and a Faradaic efficiency of 73.3 % but also provides a long-term stability of Cuδ+ , gaining an economic profit based on techno-economic analysis. The calculation and in situ spectroscopic results reveal that the abundant Cuδ+ sites display electron-donating ability, leading to the decrease of the reaction barrier in the potential-determining C-C coupling step and eventually making the applied potential close to the theoretical value.