Silver (Ag) is the state-of-the-art electrocatalyst for selective carbon monoxide (CO) production from waste carbon emissions. Deng et al. (https://doi.org/10.1021/acscatal.2c00960) recently investigated the size-dependent transition between CO₂ reduction reaction and H₂ evolution reaction on silver nanoparticle electrocatalysts. Ag nanoparticles were grown under ultrahigh vacuum (UHV) via metal evaporation onto highly oriented pyrolytic graphite (HOPG) substrate. The results showed that CO₂RR rates increased while HER rates decreased when the particle size increased from 2 to 4nm. 3.7 ± 0.7 nm diameter particles demonstrated the highest combination of CO₂RR activity and selectivity. This is consistent with the computational modelling of 1-10nm Ag particles with maximum CO₂RR activity on 3.7nm Ag particles. Smaller particles favor HER due to a high population of Ag edge sites. CO₂RR activity increases for larger particles as the population of Ag(100) surface sites grow. However, a growing population of electrochemically inaccessible, interior atoms eventually decreased catalyst utilization for particle diameters above ∼4 nm. Years ago, Dioxide Materials showed similar size dependent of Ag particle catalysts on the activity of CO₂RR( https://doi.org/10.1021/jp310509z).

Electrochemical evaluation of CO₂ reduction reaction (CO₂RR) was conducted in CO₂-saturated 0.1M KHCO₃ using an H-cell in Deng’s paper, but in EMIM-BF₄ containing 75ppm of water using three-electrode glass cell. Dioxide Materials have improved the current density of CO₂RR by two orders of magnitude using gas-feed zero-gap cells where unique Sustainion anion exchange membranes were employed as compared to traditional electrochemical cells used in Deng’s paper (2022) and previous Dioxide Materials’ paper (2013).

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