Maximizing CO₂ Reduction Efficiency: Surface‐Regulated Highly Porous Ag‐Cu Alloy Aerogel Inserted With Multi‐Wall Carbon Nanotube Achieving Nearly Complete CO Selectivity

Abstract

The electrochemical reduction of CO2 (eCO2RR) holds promise in mitigating atmospheric greenhouse gas levels but is hindered by low reaction kinetics, high energy barriers, and poor selectivity. To address these challenges, we developed a novel series of cost‐effective AgCu‐containing metal‐aerogel catalysts with high electrochemical surface areas (ECSA) using a top‐down reduction approach. The Ag85Cu15 aerogel, with an ECSA of 27.41 cm², achieved a Faraday efficiency (FE%) of 89.3% for CO production at ‐0.9 V vs. RHE. Increasing the Cu content to over 50% in the aerogel matrix produced small amounts of C2H4, with a maximum FE% of 12.9% at ‐1.0 V vs. RHE. To further enhance CO2 reduction efficiency, multi‐walled carbon nanotubes (CNT) were incorporated into the Ag85Cu15 alloy aerogel via a hydrothermal treatment. The highly dispersed CNTs within the aerogel matrix increased the ECSA to 57.00 cm² by forming a well‐defined porous structure through van‐der Waals interactions, improving CO selectivity, and achieving a FE% of 98.6% at ‐0.7 V vs. RHE and a partial current density of 9.6 mA/cm² in an H‐cell. 86% of the initial FECO% was maintained during an 18 h test with continuous electrolysis.