Hydrophobic modification regulates the water microenvironment at the interface of Cu-based materials to promote E-CO 2 RR

Key numbers

• 45.2% Faradaic efficiency for ethylene

Electrocatalytic CO2 reduction (E-CO2RR) powered by renewable energy is vital for carbon cycling and carbon neutrality. Cu-based catalysts uniquely produce multi-carbon (C2+) products, yet the interfacial water microenvironment and reaction kinetics remain poorly understood. This work fabricates hydrophobic HY-Cu2O (100) catalysts by self-assembling octadecanethiol on cubic (100)-faced Cu2O nanoparticles to tune interfacial water. Integrated characterizations, electrochemistry, and in situ Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) reveal how hydrophobicity regulates E-CO2RR performance. Hydrophilic/hydrophobic contact-angle measurements reveal that the surface wetting angle changes from 46.1° (hydrophilic) to 133.5° (hydrophobic). X-ray diffraction (XRD) confirms that the crystal structure remains unchanged. X-ray photoelectron spectroscopy (XPS) results demonstrate that the Cu-S coordination environment of the material is modified. Further inference suggests that the formation of Cu-S bonds verifies the successful functional grafting of octadecyl chains onto the Cu2O (100) surface, which alters the surface hydrophilicity/hydrophobicity without inducing any variation in the crystal structure. In 1 M KOH flow cells, HY-Cu2O delivers 45.2% Faradaic efficiency for ethylene at -250 mA∙cm-2 and suppresses parasitic Hydrogen Evolution Reaction (HER), far exceeding bare Cu2O. In situ spectra and theory verify that hydrophobic interfaces accumulate K+-bound free water, disrupt interfacial hydrogen bonds, accelerate *CO protonation, and boost C-C coupling for C2+ intermediates. Higher surface CO coverage further kinetically favors C2+ formation. This work establishes an effective hydrophobic modification approach, clarifies the central role of interfacial water in ethylene selectivity, and offers guidance for the design of advanced CO2RR catalysts.

K. Li, Yanxin Chen, Hao-Yan Shi, Hai-Long Wang, Yi-Hong Wu, Xiao-Wei Wu, Songling Wang, Yang Ding, Ai-Zhong Jia, Paolo Fornasiero, Can-Zhong Lu

Leverage2 / 5

Reusable within one subfield (a technique, dataset, or protocol a few groups will adopt).

16% of this desk’s rubric

Magnitude3 / 5

Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.

20% of this desk’s rubric

Evidence3 / 5

Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.

20% of this desk’s rubric

Novelty2 / 5

A new combination of known ideas.

10% of this desk’s rubric

Trajectory2 / 5

Some room to improve with obvious engineering.

14% of this desk’s rubric

Stakes3 / 5

Meaningful benefit to many people within a few years.

20% of this desk’s rubric

• Citations0 (reference 15, via openalex, Oct 31, 2026, 07:20 UTC)

• Reviewed by heuristic-v10 on Oct 31, 2026, 07:20 UTC. Paper type: empirical.
• Categories: CO2 Reduction Techniques and Catalysts, Electrocatalysts for Energy Conversion, Advanced Photocatalysis Techniques, Renewable Energy, Sustainability and the Environment, Energy
• BRIEF, No.5 in the Climate & Energy edition of October 31, 2026.