Thiocyanate-Modified Silver Nanofoam for Efficient CO₂ Reduction to CO

Abstract

Ag is a promising electrocatalyst for electrochemical reduction of CO 2 to CO due to its relatively low cost and high activity. However, it is challenging to achieve high reaction rates while maintaining good selectivity. Here, we used an H 2 bubbletemplated electrodeposition method in a thiocyanate (SCN)containing aqueous electrolyte to synthesize a hierarchically porous Ag nanofoam (AgNF) with curved Ag surfaces modified by SCN. This AgNF demonstrates excellent performance for CO 2 reduction with a high CO Faradaic efficiency (FE CO ) of 97%. It can maintain over 90% FE CO in a wide potential window (−0.5 to −1.2 V RHE ), enabling the maximum CO selective current density of 33 mA cm −2 and the mass activity of 23.5 A g Ag −1, which are the highest values among recently reported Ag-based electrocatalysts. Mechanism studies reveal that the catalytic performance of the AgNF correlates with the density of surface SCN ligands, which exhibit excellent electrochemical stability under negative potentials. Density functional theory calculations suggest that SCN ligands promote the formation of COOH* intermediates by modifying the local electron density at the active sites. Further, the synthesis method is applicable to different catalyst substrates. For example, the AgNF grown on a carbon-based gas diffusion film exhibits an ultrahigh mass activity of 52.1 A g Ag −1 and maintains its high CO selectivity simultaneously, demonstrating excellent potentials for practical applications.

Boosting CO2 Electrochemical Reduction with Atomically Precise Surface Modification on Gold Nanoclusters

“…In order to obtain a qualitative understanding of the selectivity of the NCs towards CO 2 RR, the difference between the most energetically uphill step (represented by limiting potential “U L ”) for CO 2 RR and HER for the two NCs upon ‐R removal is presented in Table 1 as ΔU L =[U L (CO 2 RR)−U L (HER)] [8b, 26a, 27] . In this case, the formation of *CO and H 2(g) are the thermodynamic limiting steps for CO 2 RR and HER respectively on both NCs.…”

Electrocatalysts by Electrodeposition: Recent Advances, Synthesis Methods, and Applications in Energy Conversion

“…Figure 18 shows the morphological and compositional characterization study of thiocyanate modified porous silver nanofoams (AgNF) using the H 2 bubble templated electrodeposition method for CO 2 reduction to CO. [37] Figure 18a,b shows the TEM images of AgNF at different magnification. The inset of Figure 18a shows the diffraction pattern of Ag ligaments with different diffraction rings, which are assigned to several Ag facets.…”

“…But the geometric activity is often used to measure solar devices' efficacy and so Reproduced with permission. [37] Copyright 2019, ACS.…”

“…e) HAADF-STEM image and its corresponding EDX elemental mapping results. Ag and S signals are overlaid for comparison.Reproduced with permission [37]. Copyright 2019, ACS.…”

Nitrogen and Boron Co‐Doped Carbon Spheres for Carbon Dioxide Electroreduction

“…Moreover, product selectivity is limited by sophisticated CO 2 RR pathways and the competive hydrogen evolution reaction (HER) [7] . Herein, an ideal catalyst for CO 2 RR is expected to deliver large current densities and high Faradaic efficiencies toward desired products at low overpotentials [8–10] …”