Study of carbon dioxide electrochemical reduction in flow cell system using copper modified boron-doped diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | E3S Web of Conferences |
| Authors | Salsabila Zahran Ilyasa, Prastika Krisma Jiwanti, Munawar Khalil, Yasuaki Einaga, Tribidasari A. Ivandini |
| Institutions | Keio University, Airlangga University |
| Citations | 4 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study investigates the use of copper-modified Boron-Doped Diamond (Cu-BDD) electrodes in a flow cell system for enhanced CO2 electrochemical reduction (CO2R).
- Core Value Proposition: Cu modification significantly improves the catalytic activity of BDD electrodes, specifically enhancing the production of formic acid (HCOOH) from CO2.
- Optimal Electrode Performance: The Cu-BDD 100s electrode (100 seconds Cu deposition) showed the best characteristics, achieving a Cu mass percentage of 0.83% and uniform nanoparticle distribution (~148 nm).
- Key Achievement (HCOOH Production): The Cu-BDD 100s electrode achieved a Faradaic Efficiency (FE) of 33.00% for formic acid production at -1.5 V (vs. Ag/AgCl).
- Performance Comparison: This HCOOH efficiency (33.00%) is more than double the efficiency observed using a bare BDD electrode (14.69%) under identical flow cell conditions.
- Flow Cell Selectivity: The use of a flow cell system, compared to static cells, suppressed the formation of C2/C3 hydrocarbon products, instead favoring C1 products (HCOOH, CO, CH4) and hydrogen evolution.
- Electrode Stability: Post-reduction analysis showed that a significant portion of the deposited Cu particles (97.59% mass decrease) detached from the BDD surface, indicating a potential stability challenge under continuous operation.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Working Electrode Substrate | Boron-Doped Diamond (BDD) | N/A | Prepared on Si(100) wafers via MPCVD. |
| Optimal Cu Deposition Time | 100 | seconds | Used for Cu-BDD 100s electrode variant. |
| Cu Deposition Potential | -0.6 | V | Applied during chronoamperometry (vs. Ag/AgCl). |
| CO2 Reduction Potential | -1.5 | V | Applied during electrolysis (vs. Ag/AgCl). |
| Working Electrode Area | 9.62 | cm2 | Area exposed in the two-compartment flow cell. |
| Catholyte Composition | 0.5 M KCl | 50 mL | Electrolyte used in the cathode chamber. |
| Anolyte Composition | 0.1 M KOH | 50 mL | Electrolyte used in the anode chamber. |
| Gas Flow Rate (CO2/N2) | 200 | sccm | Bubbling rate before and during reduction. |
| HCOOH Faradaic Efficiency (Cu-BDD 100s) | 33.00 | % | Highest efficiency product. |
| HCOOH Concentration (Cu-BDD 100s) | 11.33 | mg/L | Concentration of the main liquid product. |
| Hydrogen (H2) Faradaic Efficiency (Cu-BDD 100s) | 21.25 | % | Competing reaction efficiency. |
| Carbon Monoxide (CO) Faradaic Efficiency | 1.67 | % | Gaseous product efficiency (Cu-BDD 100s). |
| Methane (CH4) Faradaic Efficiency | 0.05 | % | Gaseous hydrocarbon product efficiency. |
| Cu Mass Percentage (Pre-Reduction) | 0.83 | % | Cu-BDD 100s composition (EDX). |
| Cu Mass Decrease (Post-Reduction) | 97.59 | % | Indicates significant Cu particle detachment. |
Key Methodologies
Section titled âKey MethodologiesâThe experimental procedure involved BDD preparation, copper electrodeposition, electrode characterization, and CO2 electrochemical reduction in a flow cell.
- BDD Preparation: Boron-doped diamond films were grown on Si(100) wafers using Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD).
- Copper Electrodeposition:
- Method: Chronoamperometry in a one-compartment cell.
- Electrolyte: 1 mM CuSO4 in 0.1 M H2SO4.
- Conditions: Applied potential of -0.6 V (vs. Ag/AgCl).
- Optimization: Deposition time of 100 seconds (Cu-BDD 100s) was selected based on optimal Cu reduction characteristics observed via Cyclic Voltammetry (CV).
- Electrode Characterization:
- Morphology and Composition: Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX) confirmed uniform Cu particle distribution (~148 nm) on the Cu-BDD 100s surface.
- Chemical State: X-Ray Photoelectron Spectroscopy (XPS) confirmed the presence of Cu0 (metallic copper) via peaks at 933 eV and 952.4 eV.
- Flow Cell Electrolysis Setup:
- Reactor: Two-compartment PTFE flow cell separated by a Nafion membrane.
- Electrodes: Cu-BDD working electrode, Ag/AgCl reference electrode, and Pt plate counter electrode.
- Electrolytes: 0.5 M KCl catholyte and 0.1 M KOH anolyte.
- Gas Management: Catholyte was purged sequentially with N2 (30 min) then CO2 (15 min) at 200 sccm. CO2 flow was maintained during the 1-hour reduction process.
- Reduction and Analysis:
- Reduction: Performed at a constant potential of -1.5 V (vs. Ag/AgCl) for 1 hour.
- Product Quantification: Liquid products (HCOOH) analyzed by High-Performance Liquid Chromatography (HPLC); gaseous products (CO, CH4, H2) analyzed by Gas Chromatography (GC).
Commercial Applications
Section titled âCommercial ApplicationsâThe technology developed, leveraging the stability of BDD and the catalytic activity of copper for CO2 reduction, is relevant to several high-tech and industrial sectors.
- Carbon Capture and Utilization (CCU): Direct electrochemical conversion of industrial CO2 emissions into valuable chemical feedstocks (e.g., formic acid), offering a pathway for carbon recycling.
- Industrial Chemical Synthesis: Production of Formic Acid (HCOOH), a crucial chemical used in agriculture, leather processing, and chemical synthesis, via a low-temperature, low-pressure electrochemical route.
- Electrochemical Reactor Engineering: Design and deployment of robust flow cell reactors for continuous, high-throughput CO2R processes, utilizing BDDâs chemical inertness and wide potential window.
- High-Performance Electrodes: The use of BDD as a stable, conductive substrate for metal nanoparticle catalysts (Cu, Pd, Ir) is essential for developing next-generation electrodes for electrocatalysis and sensing.
- Hydrogen Economy: While the primary goal was HCOOH, the system also produced H2 (21.25% FE), indicating potential for co-production of hydrogen fuel alongside valuable chemicals.
- Wastewater Treatment (Related BDD Application): The BDD substrate itself is widely used in Advanced Oxidation Processes (AOPs) for the degradation of persistent organic pollutants due to its high stability and ability to generate hydroxyl radicals.
View Original Abstract
High concentrations of CO2 in the atmosphere may cause climate and environmental changes. Therefore, various research has been extensively performed to reduce CO 2 by converting CO 2 directly into hydrocarbons. In this research, CO 2 electrochemical reduction was studied using boron-doped diamond (BDD) modified with copper nanoparticles to improve BDD electrodesâ catalytic properties. The deposition was performed by chronoamperometry technique at a potential of -0.6 V (vs. Ag/AgCl) and characterized using SEM, EDS, XPS, and cyclic voltammetry (CV). CO 2 electrochemical reduction on BDD and Cu-BDD was carried out at -1.5 V (vs. Ag/AgCl) for 60 minutes. The products were analyzed using HPLC and GC. The product was mainly formic acid with a concentration of 11.33 mg/L and 33% faradaic efficiency on a Cu-BDD electrode.