Maintaining local alkalinity of CO-electroreduction full cell by silica-confined electrocatalysts in membrane electrode assembly

Jing, Shuangxi 1 ; Wang, Gongwei1 ; Li, Zhe 2 ; Xiao, Wei 1 ; Zhuang, Lin 1

Published Nov 14, 2025 on Dryad. https://doi.org/10.5061/dryad.rv15dv4mp

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Abstract

CO electroreduction in alkaline membrane electrode assembly represents an effective approach to achieve carbon neutrality. However, its performance is currently limited by the insufficient modulation of local alkalinity at a full cell level. In this work, we reveal that confining the in-situ generated OH⁻ at cathode and enriching the bulk OH⁻ to anode are the key factors for an efficient CO-electroreduction full cell. We thereby propose a silica-confined strategy for electrocatalyst design to maintain high local alkalinity at both cathode and anode by the strong Lewis acid-base interaction between highly electrophilic Si atom and OH⁻. The developed Cu/SiO₂ cathode and Co/SiO₂ anode successfully promote cathodic multi-carbon formation and anodic oxygen evolution, thereby improving the full cell energy efficiency. Even under high-rate electrolysis at 900 mA cm ⁻², the selectivity and energy efficiency of multi-carbon products remains above 80% and 30%. This achievement highlights the significance of modulating the dynamic OH⁻ transport at full cell in enhancing CO electroreduction performance.

Dataset DOI: 10.5061/dryad.rv15dv4mp

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All data generated or analyzed during this study are included in the paper and the Supplementary Materials.

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Fig. 1C Measurement on anolyte OH⁻ transport across AEM under open circuit voltage (OCV).

Fig. 1D In-situ OH⁻ adsorption curves recorded on Cu electrode before and after CORR at −100 mA cm⁻² in 1 M KCl.

Fig. 1E CORR performances on Cu cathodes modified with CEI (i.e. Nafion) or AEI (i.e. QAPPT).

Fig. 1G In-situ OH⁻ adsorption curves recorded on Cu electrode after CORR or hydrogen evolution reaction (HER) at different current densities in 1 M KCl.

Fig. 2D Cu K-edge XANES spectra of Cu, Cu/SiO₂ and the reference materials.

Fig. 2E Fourier-transformed Cu K-edge EXAFS spectra of Cu, Cu/SiO₂ and the reference materials.

Fig. 2F Wavelet transformation plots of Cu K-edge EXAFS spectra of Cu, Cu/SiO₂ and the reference materials.

Fig. 3A Adsorption energy (E_ad) of *OH on different Si and Cu sites of Cu/SiO₂.

Fig. 3B OH⁻ adsorption curves recorded on Cu/SiO₂ and Cu electrodes in 1 M KOH.

Fig. 3C ECSA normalized K⁺ adsorption on Cu/SiO₂ and Cu electrodes.

Fig. 3D left In-situ Raman spectra during CORR recorded on Cu/SiO₂ and Cu electrodes.

Fig. 3D right In-situ Raman spectra during CORR recorded on Cu/SiO₂ and Cu electrodes.

Fig. 3E FE of all products during CORR on Cu/SiO₂.

Fig. 3F FE of C₂₊ products on Cu/SiO₂ and Cu.

Fig. 3G Current densities of C₂₊ products and cell voltages by using Cu/SiO₂ and Cu.

Fig. 3H Free energy diagrams for 2*CO coupling to *OCCO on Cu and Cu/SiO₂.

Fig. 4A Cell voltages recorded in 0.5 M K₂SO₄ or 1 M KOH at 100 mA cm⁻² with Cu cathode and IrO₂ anode.

Fig. 4D In-situ Raman spectra during OER recorded on Co/SiO₂ and Co electrodes.

Fig. 4E LSV curves for OER recorded on Co/SiO2, Co and IrO2 electrodes at 5 mV s−1 in 1 M KOH.

Fig. 4F EIS results recorded at 1.53 V vs. RHE on Co/SiO₂, Co and IrO₂ electrodes from 100 kHz to 0.1 Hz with 5 mV amplitude.

Fig. 4G Comparation on the R_ct of Co/SiO₂ and IrO₂ electrodes at different applied potentials.

Fig. 4H LSV curves for MOR recorded on Co/SiO₂ and IrO₂ electrodes at 5 mV s⁻¹ in 1 M KOH with 1 M methanol.

Fig. 4I Potential change from OER to MOR on Co/SiO₂ and IrO₂ electrodes at 100 mA cm⁻².

Fig. 4J OER durability test on Co/SiO₂ electrode in 1 M KOH at 100 mA cm⁻².

Fig. 5A FE of all products during CORR with Cu/SiO₂ cathode, Co/SiO₂ anode and 1 M KOH anolyte.

Fig. 5B Comparation on cell voltage with different cathode and anode configurations.

Fig. 5C Comparation on EE of C₂₊ products with different cathode and anode configurations.

Fig. 5D Comparation on current density of C₂₊ products with different cathode and anode configurations.

Fig. S1B XRD pattern of Cu nanoparticles.

Fig. S1C XPS spectra of Cu 2p of Cu nanoparticles.

Fig. S1D XPS spectra of Cu LMM of Cu nanoparticles.

Fig. S2 CORR performances of Cu electrode in flow cell and MEA with different electrolytes.

Fig. S4B LSV curves for OER recorded on IrO₂ electrode modified with AEI (i.e. QAPPT) and CEI (i.e. Nafion) at 5 mV s⁻¹ in 1 M KOH.

Fig. S4C left Bode plots recorded at different potentials. From 100 kHz to 0.1 Hz with 5 mV amplitude.

Fig. S4C right Bode plots recorded at different potentials. From 100 kHz to 0.1 Hz with 5 mV amplitude.

Fig. S7A XRD patterns of Cu silicate and Cu/SiO₂.

Fig. S7B XPS spectra of Cu 2p of Cu silicate and Cu/SiO₂.

Fig. S7C XPS spectra of Cu LMM of Cu silicate and Cu/SiO₂.

Fig. S7D XPS spectra of Si 2p of Cu silicate and Cu/SiO₂.

Fig. S8A Pb stripping curves recorded on Cu electrode.

Fig. S8B Pb stripping curves recorded on Cu/SiO₂ electrode.

Fig. S9 Energy and temperature evolutions of Si₆O₁₃ cluster on Cu (111) surface by machine learning force field ab initio molecular dynamics at 1000 K.

Fig. S11A NH₃ TPD-MS test of Cu/SiO₂ and Cu. TCD signals.

Fig. S11B NH₃ TPD-MS test of Cu/SiO₂ and Cu. MS signals.

Fig. S12A EIS results recorded at a cell voltage of 2.0 V with Cu/SiO₂ and Cu cathodes. From 100 kHz to 0.1 Hz with 5 mV amplitude.

Fig. S12B TOF of C₂₊ products on Cu/SiO₂ and Cu cathodes. The calculation is based on Cu site.

Fig. S12C SPCE on Cu/SiO₂ and Cu cathodes. The gas flow rate is 5 mL/min and the CO content is 95%.

Fig. S13A E_ad of 2*CO and *OCCO on Cu/SiO₂ and Cu.

Fig. S13B Density of states of Cu/SiO₂ and Cu with adsorbed *OCCO.

Fig. S14A FE of all products during CORR on Cu.

Fig. S14C Free energy diagrams for *OCCOH to *HOCCOH or *CCO on Cu.

Fig. S14D Free energy diagrams for *OCCOH to *HOCCOH or *CCO on Cu/SiO₂.

Fig. S15 CORR performances on Cu and Cu/SiO₂ cathodes modified with different fractions of CEI (i.e. Nafion).

Fig. S18A XRD patterns of Co silicate and Co/SiO₂.

Fig. S18B XPS spectra of Co 2p of Co silicate and Co/SiO₂.

Fig. S18C XPS spectra of Si 2p of Co silicate and Co/SiO₂.

Fig. S19 E_ad of *OH on Si sites and Co sites.

Fig. S22A Free energy diagram for *OH migration from Si to Co.

Fig. S22B Free energy change for *OH migration from Si to Co and the rate-determining step (RDS, *O to *OOH) of OER on Co.

Fig. S23 Free energy diagrams for OER on Co with different *OH coverages.

Fig. S24A NH₃ TPD-MS test of Co/SiO₂ and Co. TCD signals.

Fig. S24B NH₃ TPD-MS test of Co/SiO₂ and Co. MS signals.

Fig. S25B XRD pattern of Co nanoparticles.

Fig. S25C XPS spectra of Co 2p of Co nanoparticles.

Fig. S26A CV curves recorded on Co/SiO₂ and Co electrodes in 0.1 M KOH.

Fig. S26B Redox potentials of Co/SiO₂ and Co electrodes.

Fig. S27A LSV curves for MOR and OER recorded on Co/SiO₂ electrode.

Fig. S27B LSV curves for MOR and OER recorded on IrO₂ electrode.

Fig. S28A LSV curves for OER recorded on Co/SiO₂ electrode at 5 mV s⁻¹ in 1 M KOH before and after adding 0.1 M thiourea.

Fig. S28B Current density variation at 1.68 V vs. RHE before and after adding thiourea.

Fig. S29 Full cell CO electrolysis durability.