Electrochemical reduction of carbon dioxide to acetic acid on a Cu–Au modified boron-doped diamond electrode with a flow-cell system
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-01-01 |
| Journal | RSC Advances |
| Authors | Millati H. Saprudin, Prastika Krisma Jiwanti, Deden Saprudin, Afiten R. Sanjaya, Yulia Mariana Tesa Ayudia Putri |
| Institutions | Keio University, Airlangga University |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research details the optimization and performance of a bimetallic catalyst system for the electrochemical reduction of carbon dioxide (CO2RR) to valuable organic acids (formic acid and acetic acid) using a flow-cell reactor.
- Core Technology: Boron-Doped Diamond (BDD) electrodes modified with copper and gold nanoparticles (CuAu-BDD) via electrodeposition were used as the working electrode.
- System Advantage: The flow-cell system significantly accelerated the production rate of acetic acid and reduced the optimal CO2 reduction potential from -1.5 V (for Cu-BDD) to -1.0 V (for CuAu-BDD).
- Optimal Performance: Maximum Faradaic Efficiency (FE) for formic acid (HCOOH) was 40.31% achieved at -1.0 V (vs. Ag/AgCl) using the CuAu-BDD electrode.
- Productivity: The highest formic acid production rate was 4.88 mol m-2 s-1, yielding a concentration of 15.93 ppm. Acetic acid (CH3COOH) was produced at 0.11 mol m-2 s-1 (3.63% FE).
- Stability Improvement: The bimetallic CuAu modification provided superior stability for the deposited metal particles on the BDD surface compared to electrodes modified with single metals (Cu-BDD or Au-BDD), as confirmed by SEM-EDS analysis post-electrolysis.
- Electrode Composition: Optimal deposition times were 300 s for Cu and 100 s for Au, resulting in a CuAu-BDD surface composition of 0.12% Cu and 1.48% Au (w/w).
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimum Applied Potential | -1.0 | V (vs. Ag/AgCl) | CuAu-BDD, Flow Cell |
| Optimum Electrolyte Flow Rate | 50 | mL min-1 | CO2 Electroreduction |
| Formic Acid Production Rate (Max) | 4.88 | mol m-2 s-1 | CuAu-BDD at -1.0 V |
| Acetic Acid Production Rate (Max) | 0.11 | mol m-2 s-1 | CuAu-BDD at -1.0 V |
| Formic Acid Concentration (Max) | 15.93 | ppm | CuAu-BDD at -1.0 V |
| Acetic Acid Faradaic Efficiency (Max) | 3.63 | % | CuAu-BDD at -1.0 V |
| Formic Acid Faradaic Efficiency (Max) | 40.31 | % | CuAu-BDD at -1.0 V |
| CuAu-BDD Cu Content (w/w) | 0.12 | % | Post-modification elemental analysis |
| CuAu-BDD Au Content (w/w) | 1.48 | % | Post-modification elemental analysis |
| Cu-BDD Optimal Deposition Time | 300 | s | For maximum HCOOH production |
| Au-BDD Optimal Deposition Time | 100 | s | For maximum HCOOH production |
| Electrolyte Composition | 0.5 M | KCl | Standard CO2RR solution |
| CO2 Aeration Time (Optimum) | 15 | min | To achieve maximum dissolved CO2 |
Key Methodologies
Section titled “Key Methodologies”The experimental process involved BDD electrode preparation, bimetallic modification, flow-cell setup, and product analysis:
- BDD Pre-treatment: BDD films were pre-treated by applying a potential of -2.0 V (vs. Ag/AgCl) for 15 min, followed by drying with N2 gas.
- Electrodeposition Solution: The modification solution was 0.1 M H2SO4 containing 1 mM CuSO4 and 1 mM HAuCl4.
- Bimetallic Modification (CuAu-BDD): Copper and gold particles were simultaneously deposited using a constant potential of -0.6 V (vs. Ag/AgCl) for an optimized time of 300 s.
- Electrolyte Preparation: The 0.5 M KCl electrolyte was purged with N2 for 15 min, followed by CO2 aeration for 15 min to ensure high CO2 dissolution.
- Electrolysis System: A flow-cell system was employed, utilizing the modified BDD as the working electrode, a Pt wire counter electrode, and an Ag/AgCl reference electrode.
- Flow Rate Optimization: The electrolyte flow rate was optimized at 50 mL min-1, balancing mass transport increase against technical stability issues (vibration) at higher rates.
- Product Analysis: Products (formic acid and acetic acid) were quantified using High-Performance Liquid Chromatography (HPLC) with a UV detector (210 nm).
- Characterization: Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to confirm metal deposition and assess particle stability before and after electrolysis.
Commercial Applications
Section titled “Commercial Applications”This technology, leveraging the stability of BDD and the catalytic activity of bimetallic Cu-Au, is highly relevant to several industrial sectors:
- Carbon Capture and Utilization (CCU): Provides a pathway for converting waste CO2 streams directly into valuable liquid chemical feedstocks (formic acid, acetic acid) at ambient temperature and pressure.
- Sustainable Chemical Manufacturing: Enables the green synthesis of commodity chemicals, reducing reliance on fossil fuel-derived processes for formic acid (used in preservation, leather tanning) and acetic acid (used in polymers, solvents).
- Electrochemical Reactor Design: The successful implementation of the flow-cell system demonstrates a scalable, continuous reactor design suitable for industrial electrochemical synthesis, offering advantages over traditional batch processes.
- High-Stability Electrode Technology: BDD’s intrinsic chemical and physical stability, combined with enhanced metal particle adhesion, makes these electrodes ideal for long-term operation in corrosive or demanding electrochemical environments.
- Energy Storage/Fuel Cells: Formic acid is a potential hydrogen carrier; efficient production via CO2RR supports the development of direct formic acid fuel cells.
View Original Abstract
Boron-doped diamond (BDD) was modified with copper and gold particles by using an electrodeposition technique to improve its catalytic effect on CO 2 reduction in a flow system.