Amorphous CuSBox Composite-Catalyzed Electrocatalytic Reduction of CO2 to CO: CO2 Demand-Supply-Regulated Performance

Physical Chemistry Energy Chemistry Chemistry Catalysis Materials Science
electrocatalytic reduction CO2 amorphous CuSBox demand-supply relationship gas diffusion electrode

Academic Background

As the issue of global climate change intensifies, reducing carbon dioxide (CO2) emissions and seeking sustainable energy solutions have become major directions in scientific research. Electrocatalytic CO2 reduction (CO2RR) is a green technology that converts CO2 into value-added chemicals and fuels, holding enormous application potential. However, despite significant progress in this field, CO2RR still faces many challenges in practical applications, especially achieving efficient and selective production of target products under high current densities. One main problem is the low solubility of CO2 in the electrolyte, leading to insufficient CO2 supply at the cathode surface and limiting reaction efficiency.

To overcome this issue, researchers have focused on developing novel electrocatalysts and exploring the dynamic relationship between CO2 demand and supply. This study utilizes in-situ synthesis of amorphous copper antimony oxide (CuSbOx) cathodes to systematically investigate the effect of CO2 demand and supply on catalytic performance in CO2RR, revealing the decisive role of CO2 supply capacity in electrocatalytic performance.

Article Source

This paper was collaboratively completed by researchers Huai Qin Fu, Tingting Yu, Jessica White, and others, with the team based at Griffith University (Australia), East China University of Science and Technology, and other institutions. The paper was published on March 13, 2025, in the journal Chem, entitled “Amorphous CuSbOx Composite-Catalyzed Electrocatalytic Reduction of CO2 to CO: CO2 Demand-Supply-Regulated Performance”.

Research Process

1. Preparation of Amorphous CuSbOx Cathode

The researchers adopted an electrochemical conversion method to transform the pre-immobilized CuSbS2 precursor on carbon paper into an amorphous CuSbOx cathode under operando CO2RR conditions. The specific procedure was as follows: - Precursor synthesis: CuSbS2 precursors were synthesized via a solvothermal method, with their structure and morphology characterized by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). - Electrochemical conversion: The CuSbS2-loaded carbon paper was subjected to a cathodic potential of -1.0 V (vs. RHE) in CO2-saturated 0.5 M KHCO3 electrolyte for 1 hour, resulting in the formation of amorphous CuSbOx.

2. Evaluation of Electrocatalytic Performance

The CO2RR performance of the CuSbOx cathode was assessed in a three-electrode electrochemical system, specifically: - Current density and Faradaic efficiency: Under varying cathodic potentials and catalyst loading densities, the total current density (jtotal), CO partial current density (jco), and H2 partial current density (jh2) were measured, and the Faradaic efficiencies for CO and H2 (FEco and FEh2) were calculated. - Stability test: Continuous electrolysis was performed at -1.0 V (vs. RHE) for 27 hours to monitor jco and FEco changes.

3. Investigation of CO2 Demand and Supply Relationship

Through experimental and computational simulations, the researchers systematically examined the impact of CO2 demand and supply on the performance of the CuSbOx cathode: - Experimental study: CO2RR performance at various catalyst loading densities was evaluated in both the H-cell and a gas diffusion electrode (GDE) flow cell. - Computational simulation: A cathode/electrolyte interface model was constructed using the COMSOL Multiphysics finite element method to simulate CO2 concentration distribution and current density.

4. Structural and Chemical State Characterization

The structure and chemical state of the CuSbOx cathode were comprehensively characterized using X-ray absorption spectroscopy (XAS), Raman spectroscopy, and X-ray diffraction (XRD), confirming its stability under CO2RR conditions.

Main Findings

1. Preparation and Characterization of Amorphous CuSbOx Cathode

  • Structural characterization: XRD and Raman spectra showed that the CuSbS2 precursor was completely converted into amorphous CuSbOx, with uniform distribution of Cu, Sb, and O elements.
  • Electrochemical performance: Under -1.0 V (vs. RHE), the CuSbOx cathode achieved a jco of 27.2 mA cm⁻² and FEco of 91.2% in the H-cell, and a jco of 283 mA cm⁻² and FEco of 81.5% in the GDE flow cell.

2. CO2 Demand and Supply Relationship

  • Effect of catalyst loading density: As catalyst loading density increased, jco first rose rapidly and then plateaued, indicating that the CO2 supply reached its maximum capacity.
  • Simulation results: Simulations showed that in the H-cell, the CO2 supply capacity limited the maximal jco; in the GDE flow cell, the CO2 supply capacity was significantly improved but still remained the performance-limiting factor.

3. Structural and Chemical Stability

  • XAS analysis: Cu and Sb K-edge XAS spectra revealed that the CuSbOx cathode maintained stable Cu2O and Sb2O3 structural units under CO2RR conditions.
  • Stability test: Throughout a 27-hour continuous electrolysis, both jco and FEco remained essentially unchanged, demonstrating the excellent electrochemical stability of the CuSbOx cathode.

Conclusions and Significance

This study systematically investigated the effect of CO2 demand and supply on catalytic performance in CO2RR via in-situ synthesis of amorphous CuSbOx cathodes, highlighting the decisive role of CO2 supply capacity in electrocatalytic performance. The findings show that although the CO2 supply capacity in the GDE flow cell is markedly higher than that in the H-cell, its performance remains limited by the CO2 supply capacity. This discovery provides crucial guidance for the design and optimization of electrocatalysts and emphasizes the importance of considering CO2 supply capability when evaluating electrocatalytic performance.

Research Highlights

  1. In-situ synthesis of amorphous CuSbOx cathode: High-stability amorphous CuSbOx cathodes were directly prepared via electrochemical conversion under CO2RR conditions.
  2. Quantitative study of CO2 demand-supply relationship: The impact of CO2 demand and supply on electrocatalytic performance was systematically revealed through both experiments and computational simulations.
  3. High-performance CO2RR catalyst: In the GDE flow cell, the CuSbOx cathode achieved a jco of 283 mA cm⁻², demonstrating its application potential at high current densities.
  4. Structural and chemical stability: Multiple characterization techniques confirmed the stability of the CuSbOx cathode under CO2RR conditions, supporting its practical application prospects.

Other Valuable Information

The study also employed density functional theory (DFT) calculations, revealing the mechanism by which the synergistic effect of Cu2O and Sb2O3 enhances CO2RR activity and selectivity, thereby providing theoretical guidance for further catalyst optimization.

This research not only provides new ideas for the development of CO2RR catalysts but also offers important insights into the relationship between electrocatalytic performance and reaction conditions, possessing significant scientific value and practical application significance.