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

Abstract

The selective electrochemical CO2 reduction (ECR) to CO in aqueous electrolytes has gained significant interest in recent years due to its capability to mitigate the environmental issues associated with CO2 emission and to convert renewable energy such as wind and solar power into chemical energy as well as its potential to realize the commercial use of CO2. In view of the thermodynamic stability and kinetic inertness of CO2 molecules, the exploitation of active, selective, and stable catalysts for the ECR to CO is crucial to promote the reaction efficiency. Indeed, plenty of electrocatalysts for the selective ECR to CO have been explored, of which Ag is known as the most promising electrocatalyst for large‐scale ECR to CO due to several competitive advantages including high catalytic performance, low price, and rich reserves compared with other metal counterparts. To provide useful guidelines for the further development of efficient catalysts for the ECR to CO, a comprehensive summary of the recent progress of Ag‐based electrocatalysts is presented in this Review. Different modification strategies of Ag‐based electrocatalysts are highlighted, including exposure of crystal facets, tuning of morphology and size, introduction of support materials, alloying with other metals, and surface modification with functional groups. The reaction mechanisms involved in these different modification strategies of Ag‐based electrocatalysts are also discussed. Finally, the prospects for the development of next‐generation Ag‐based electrocatalysts are proposed in an effort to facilitate the industrialization of ECR to CO.

Roles of Oxygen Functional Groups in Carbon Nanotubes‐Supported Ag Catalysts for Electrochemical Conversion of CO2 to CO

“…Among the reported metal electrocatalysts, Au and Ag are proved to have higher activity and selectivity for CO 2 reduction to CO, which is of industrial significance as its application in syngas . Since Ag is much cheaper and more abundant than Au, it is considered as the more promising electrocatalyst for large‐scale production of CO . Therefore, tremendous efforts have been devoted to developing and improving the performance of Ag‐based catalysts for CO 2 ER, such as tuning the size and shape, alloying with other metals, and surface modification with functional polymers .…”

Metallic Porous Electrodes Enable Efficient Bicarbonate Electrolysis

“…34,35 Additionally, The high length-to-diameter ratio afforded by nanowire decoration, provided excess pores and channels for the transport of CO 2 and electrolyte that would result in a faster reaction rate. 36 The three different silver foam electrodes were tested in a flow cell under constant applied current densities of 100, 200 and 300 mA cm -2 . Control experiments were performed with a CeTech ® woven carbon cloth support containing a layer of silver nanoparticles (denoted as " GDE/control ").…”

Nanostructured Cobalt‐Based Electrocatalysts for CO2Reduction: Recent Progress, Challenges, and Perspectives

“…Although CO 2 RR has many reaction pathways leading to different reduction products, the reaction pathway is dependent on the metal catalyst. Au, Ag, and Zn prefer the production of CO, [ 10a,63 ] while Sn, Bi, In, Pb, and Sb catalysts can primarily produce HCOOH. [ 17,64 ] Particularly, Cu is the only monometallic catalysts that can produce multiple hydrocarbons as the reduction products from CO 2 RR.…”

“…Precious metals such as Ag, Au, and Pd demonstrate outstanding ECO 2 RR activity for CO production. [ 10 ] The rare‐earth metal materials such as Er, Sc, and Y also show promising catalytic performance toward ECO 2 RR because of the unique electronic properties. Due to the vulnerability of the supply markets, current strategies of CO 2 RR catalyst design for the precious and rare‐earth metal materials mainly focus on the improvement of the metal‐utilization.…”