Ordered Ag Nanoneedle Arrays with Enhanced Electrocatalytic CO₂ Reduction via Structure-Induced Inhibition of Hydrogen Evolution

Abstract

Silver is an attractive catalyst for converting CO 2 into CO. However, the high CO 2 activation barrier and the hydrogen evolution side reaction seriously limit its practical application and industrial perspective. Here, an ordered Ag nanoneedle array (Ag-NNAs) was prepared by template-assisted vacuum thermal-evaporation for CO 2 electroreduction into CO. The nanoneedle array structure induces a strong local electric field at the tips, which not only reduces the activation barrier for CO 2 electroreduction but also increases the energy barrier for the hydrogen evolution reaction (HER). Moreover, the array structure endows a high surface hydrophobicity, which can regulate the adsorption of water molecules at the interface and thus dynamically inhibit the competitive HER. As a result, the optimal Ag-NNAs exhibits 91.4% Faradaic efficiency (FE) of CO for over 700 min at −1.0 V vs RHE. This work provides a new concept for the application of nanoneedle array structures in electrocatalytic CO 2 reduction reactions.

Solar driven CO2reduction: from materials to devices

“…Catalysts that convert CO 2 into C1 products with FE close to 100% were reported in recent years. 88–92 In another study, a FE of 85% for CH 4 was also achieved on a single-atom Zn catalyst. 93 Huang et al reported copper nanowires with rich surface steps which converted CO 2 into C 2 H 4 with a FE of more than 70% over 200 h. 94 Recently, long-chain C3 to C6 hydrocarbons were produced with a sustained FE of up to 6.5% using polarized nickel catalysts.…”

“…95 The well-designed CO 2 reduction electrocatalysts promote the rapid development of catalysts for solar driven CO 2 reduction. Metal-based catalysts (including mono-metals, 96 bimetals, 89,97 classied metal catalysts into four different groups based on their main product selectivity in electrochemical CO 2 reduction: 102 (i) H 2 selective metals, such as Ti, Fe, Ni, Pt, Pd and Ga, (ii) CO selective metals, including Au, Ag and Zn, 90 (iii) formate selective metals, such as Cd, Hg, In and Sn, (iv) Cu, a unique mono-metal which can reduce CO 2 into hydrocarbons, alcohols and C2+ products. 103,104 Metals with high selectivity to certain CO 2 reduction products are also attractive when utilized as catalysts in solar driven CO 2 reduction systems.…”

Electric Double Layer Structure in Electrocatalytic Carbon Dioxide Reduction

“…In addition, they prepared ordered Ag nanoneedle arrays with different tip curvatures by vacuum thermal evaporation. [ 67 ] The results show that the higher the curvature, the stronger the aggregation effect of the tip, which leads to a higher C 2 product activity. This series of studies shows that the catalyst surface shape greatly affects the distribution of cations in the electrolyte, which in turn affects the CO 2 RR reaction.…”

Cu–Ni alloy decorating N-doped carbon nanosheets toward high-performance electrocatalysis of mildly acidic CO2 reduction

“…17,18 The electrocatalytic performance of catalysts is largely affected by their structure, crystal surface, and number of active sites. [19][20][21] Earlier, a variety of nano-structured Ag, Au, and Pd-based electrocatalysts have been studied due to their high selectivity and relatively low overpotential for CO 2 to CO in aqueous solutions. [22][23][24][25] But the scarcity of noble metals always limits their practical use.…”