Alkylamine‐Functionalized Carbon Supports to Enhance the Silver Nanoparticles Electrocatalytic Reduction of CO2 to CO

Hydrophobicity and selectivity: The contact angle images (left) show the possibility to tune the hydrophobicity of carbon by changing the chain length of alkylamine functional groups. The CO₂RR selectivity (right), produced by Ag nanoparticles (background) on carbon materials, was influenced by the functionalization: not only H₂ formation was suppressed, but also CO production was enhanced, with an optimum around 6 carbon atoms.

Abstract

Silver electrocatalysts enable the conversion of CO₂ to CO, thereby facilitating the transition to a carbon neutral society. To lower the cost of the expensive metal, silver nanostructures are often supported on carbon. This substrate offers great electrical conductivity, but it enhances the selectivity towards the competing hydrogen evolution reaction. In this work, carbon supports were functionalized with linear alkylamines of different chain lengths, to understand its effect on electrochemical performance. Alkylamines interact with the carbon surface and confer hydrophobic properties to the carbon support as well as making the local environment less acidic. These properties led not only to a suppression of the hydrogen evolution, but also to a remarkable enhancement in CO production. Despite the low silver weight loading (0.0016 mg_Ag cm⁻²), hexylamine-functionalized carbon-based catalysts achieved a CO to H₂ ratio of 2.0, while the same material without the alkylamine functionalization only reached a ratio of 0.3, at −1.3 V vs RHE. This demonstrates the potential of hydrophobic functionalization for enhancing the CO selectivity of carbon-supported catalysts.

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