Siyu Hou,Xiya Peng,Qin Yu,Shufang Gao,Lu Li,Jian Luo
Eutectogels have emerged as versatile materials for wearable electronics, optical sensors, and biomedical applications. This study introduced the first investigation of microenvironmental basicity in poly(vinyl alcohol)/choline chloride (PVA/ChCl) eutectogels using lumichrome as a fluorescent probe. The incorporation of ChCl was demonstrated to enhance the microbasicity of PVA films, as evidenced by the significant promotion of lumichrome deprotonation. In contrast, no deprotonation occurred in deep eutectic solvents ethaline [n(ChCl):n(ethylene glycol) = 1:2], glyceline [n(ChCl):n(glycerol) = 1:2], and ChCl–water mixtures [n(ChCl):n(H2O) = 1:3 and 1:4]. Therefore, the proton acceptor in PVA/ChCl eutectogels was bound water, the same as in PVA films. Differential scanning calorimetry (DSC) experiments determined a decrease of water content in PVA films after ChCl incorporation, supporting the increased proportion of bound water in PVA/ChCl eutectogels. Our findings not only certified the enhanced microbasicity of bound water but also established a simple yet effective strategy to tune PVA films’ acid–base properties through ChCl loading.
Electrochemical CO 2 reduction (CO 2 RR) in acidic media circumvents carbonate crossover and salt precipitation inherent to alkaline and neutral systems, but suffers from low selectivity due to the dominance of hydrogen evolution. While alkali cations suppress proton activity, they inevitably lead to catastrophic (bi)carbonate deposition and electrode flooding. Here, we decouple CO 2 RR from alkali cations by constructing a micro-alkaline catalytic environment using a proton-blocking hydrophobic membrane with tethered cations. We designed a series of quaternized copolymers from dimethylaminoethyl methacrylate and lauryl methacrylate (qDMA-n), where the “cation–hydrophobicity balance” was precisely tuned to optimize the balance between Donnan exclusion and water management. Integrated into a zero-gap membrane electrode assembly electrolyzer, the optimized membrane enabled CO 2 RR on Ag catalysts with a CO faradaic efficiency of 96.9 % and a single-pass conversion efficiency of 92.4 % at 200 mA cm⁻ 2 in pure 0.05 M H 2 SO 4 , maintaining stable operation for over 100 h. Finite element simulations, rotating disk electrode tests and in-situ Raman spectra revealed that the balance between cationic and hydrophobic domains plays a key role in forming a stable micro-alkaline interface despite bulk acidity, leading to effective HER suppression. This work provides a practical and generalizable interface design principle for efficient CO 2 electrolysis in strong acids, offering new opportunities for durable, high-efficiency CO 2 electrolyzers without alkali cations.
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