Copper-deposited basalt fiber fabric for electrochemical CO2 reduction to ethanol with 98 % selectivity

Electrochemical CO2 reduction reaction (eCO2RR) to multi-carbon (C2+) products, such as ethanol is critical for sustainable energy and carbon neutrality. Traditional copper (Cu) is a promising electrocatalyst for eCO2RR, particularly for multi-carbon product formation, yet it often suffers from limitations in density, mechanical strength, corrosion resistance, and C2+ selectivity and stability. To address these challenges, this study proposes basalt fiber fabric (BFF), derived from volcanic rock, as a novel Cu electrocatalyst support. Leveraging its low density, exceptional mechanical and chemical stability, and corrosion resistance to overcome the drawbacks of Cu catalysts, a facile electroless Cu deposition was utilized to transform insulating BFF into a conductive material, resulting in a uniform Cu deposition with 96.79 wt.% Cu content. The resulting Cu-deposited BFF demonstrated a significantly reduced density of 3.08 ± 0.4 g/cm3 compared to commercial Cu (8.96 g/cm3), improved mechanical performance (breaking forces of 3308 ± 25 N warp and 665 ± 20 N weft), and high electrical conductivity (4.81 × 105 S/m before eCO2RR, decreasing slightly to 4.58 × 105 S/m post-reaction). Electrochemical characterization conducted in CO2-saturated KHCO3 electrolytes (0.1 M–2.0 M) revealed a substantial increase in electrochemical surface area (ECSA), reaching 150 cm2 in 0.1 M KHCO3 and peaking at 4250 cm2 in 1.5 M KHCO3. In 0.1 M KHCO3, the catalyst achieved a current density of 25.93 mA/cm2 with a Faradaic efficiency (FE) of 97.01 % for ethanol at −0.8 V vs reversible hydrogen electrode (RHE) in an H-type cell. Notably, performance significantly improved in 1.5 M KHCO3, yielding a current density of 184.51 mA/cm2 and a FE of 98.02 % for ethanol. Furthermore, the Cu-deposited BFF demonstrated exceptional stability, retaining 98.8 % and 99.6 % of its initial current density after 100 h of continuous operation in 0.1 M and 1.5 M KHCO3, respectively. This study establishes BFF as a novel, multifunctional support enabling robust, high-performance Cu-based eCO2RR, demonstrating exceptional durability and catalytic efficiency for efficient CO2 conversion and climate change mitigation.