Cationic carbon nanotube modulates surface fields for general acidic CO<sub>2</sub> reduction with aqueous organic cations.

Zhang, Qiang; Kwon, Soonho; Guo, Yan; Feng, Tanglue; Su, Jianjun; Song, Yun; Guo, Weihua; Xin, Yinger et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

The (bi)carbonate formation in neutral or alkaline media severely limits the carbon and energy efficiency of electrochemical CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR). Alkali metal cations and polymer coatings employed to inhibit hydrogen evolution reaction (HER) during acidic CO<sub>2</sub>RR often exacerbate salt precipitation or increase cell resistivity. Here we report cationic carbon nanotubes (CCNTs) as universal additives enabling efficient CO<sub>2</sub>RR in strong acids. Using bismuth, silver, and copper oxide catalysts, we attain Faradaic efficiency (FE) of 95%, 100%, and 67% for HCOOH, CO, and C<sub>2</sub>H<sub>4</sub> in pH≤1 electrolyte. Notably, while organic cations typically suffer from poor proton shielding and inferior selectivity, CCNT additives enable their use as electrolytes for selective acidic CO<sub>2</sub>RR. Their higher solubility permits elevated concentrations, improving stability and energy efficiency. Quantum Mechanics reveals that CCNTs physically mixed with metal catalysts alter the distribution of electric field at the electrolyte/electrode interfaces, impeding HER by suppressing hydronium ions migration while promoting CO<sub>2</sub>RR. These findings highlight CCNTs as versatile and effective additives for advancing acidic CO<sub>2</sub>RR with improved selectivity, carbon efficiency, energy efficiency, and stability.