No abstract

Aqueous electrocatalytic reduction of CO 2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multi-carbon products (C 2 /C 3), however competing proton reduction to hydrogen is an ever-present drain on selectivity. Herein, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained 56% Faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO 2 at the electrode|solution interface and consequently increase CO 2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO 2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts.

It is generally believed that CO2 electroreduction to multicarbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu-N-C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN4 coordination environment, atomically dispersed in a nitrogen-doped conductive carbon matrix. This material achieves aqueous CO2 electroreduction to ethanol at a Faradaic yield of 55% under optimized conditions (electrolyte: 0.1 M CsHCO3 , potential:-1.2V vs. RHE and gas-phase recycling set up), as well as CO electroreduction to C2-products (ethanol and ethylene) with a Faradaic yield of 80%. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis.