Surface Oxidized Ag Nanofilms Towards Highly Effective CO2 Reduction

The electrocatalytic CO2 reduction (converting redundant CO2 into carbon‐neutral fuels) holds a great potential to battle the energy and environmental crisis. The Ag‐based materials stand out from the pool of catalysts because of its high Faradic efficiencies for CO formation. In this work, thin Ag polycrystalline film was synthesized on carbon papers by a simple vacuum evaporation method. After 15 minutes of O3 treatment under ambient temperature, the Ag electrocatalysts can produce CO with a Faradic efficiency of up to 93.3 % at −0.9 V versus reversible hydrogen electrode (vs. RHE), which is higher than that of pristine Ag. In addition, the Ag electrode retained ∼90 % catalytic selectivity for CO after a 10‐hour test. The characterizations show that the surface AgxO layer on Ag was reduced to Ag0, which not only reduces the activation energy barrier of the initial electron transfer but also provides an increased number of active sites for the reduction of CO2 to CO. A 200 nm thick Ag/AgxO film is fabricated on carbon papers by physical vapor deposition method followed by a 15‐min O3 treatment. The as‐prepared Ag electrode with a thin amorphous AgxO surface layer is used as an efficient CO2 reduction catalyst, which shows a high Faradic efficiency of 93.3 % for CO production at −0.9 V vs. RHE, as well as good stability.