Facet Sensitivity of Capping Ligand‐Free Ag Crystals in CO₂ Electrochemical Reduction to CO

Abstract

Silver‐based electrocatalysts are active in catalyzing electrochemical reduction of CO2 to CO. We herein report synthesis of capping ligand‐free Ag cubes and octahedra by morphology‐preserved CO reduction from corresponding Ag2O counterparts and their performance in electrochemical reduction of CO2. Ag cubes are much more active than Ag octahedra and exhibit a stable CO formation rate as high as 142.4 mmolCO gcat−1 h−1 at −0.95 V (vs. RHE). Ag films transiently formed on Ag2O crystals during CO2 electroreduction were observed more active than Ag crystals, revealing a promoting effect of Ag2O substrate on electrocatalytic activity of Ag film. These results clearly identify a facet sensitivity of silver electrocatalysts and highlight the importance of surface cleanness of Ag colloids as efficient electrocatalysts.

A Disquisition on the Active Sites of Heterogeneous Catalysts for Electrochemical Reduction of CO2 to Value‐Added Chemicals and Fuel

“…To be more specific, Ag (110) is demonstrated to exhibit a j CO which is five times larger than that of Ag(111) and Ag(100) at an applied potential of −1.44 V . Similar findings were also reported with capped ligand‐free Ag crystals (c‐Ag), where c‐Ag catalyst with exposed (110) facet demonstrated a much lower charge transfer resistance compared to other control catalysts that were exposing only (111) facets, respectively . In addition to Ag(110) facets, it was also discovered that optimal edge‐to‐corner ratio can improve the catalytic selectivity of CO 2 RR to CO as the edge sites can lower the energy barrier for the rate determining *COOH radicals, as indicated by DFT calculations .…”

Rational Design of Ag‐Based Catalysts for the Electrochemical CO2 Reduction to CO: A Review

“…It was also reported that structure, morphology, size, and composition of the catalyst can lead to adsorption and decoupling site preferences of different adsorbates of C bound on the surface and further result in the breaking of the linear scaling relationships and tuning of the adsorption strength, eventually exerting a dramatic influence on the ECR performance . Indeed, in addition to polycrystalline and single‐crystalline Ag, some new A types have been developed and characterized recently, such as nanostructured Ag with different sizes, supported Ag catalysts with different substrates including C, TiO 2 , Al 2 O 3 , dopant‐aided Ag, oxide‐derived Ag, and surface‐modified Ag …”

“…Clearly, tuning of nanocrystalline Ag electrocatalysts in terms of their geometrical parameters such as size and shape plays a significant role in the improvement of catalytic performance for selective ECR to CO. Indeed, the impact of both particle size and nanomorphology of Ag electrocatalysts has been widely reported for selective ECR to CO in literature …”

“…In another report, Ag cubes were also found to exhibit a high CO formation rate of 142.4 mmol CO g cat .−1 h −1 at −0.95 V vs. RHE in the ECR to CO, surpassing that of Ag octahedra. The increased catalytic performance was due to the maximal fraction of active Ag(100) facets on the cubic Ag . Ham et al.…”

Strategies for Designing Nanoparticles for Electro‐ and Photocatalytic CO2 Reduction

“…Huang et al. compared cubic and octahedral Ag NPs, representing (100) and (111) surfaces, respectively, and the higher CO current on the cubic NPs confirmed strong facet dependency of Ag …”