Continuous Production of Ethylene and Hydrogen Peroxide from Paired Electrochemical Carbon Dioxide Reduction and Water Oxidation
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-03-14 |
| Journal | Advanced Energy Materials |
| Authors | Sotirios Mavrikis, Matthian Nieuwoudt, Maximilian Göltz, Sophie Ehles, Andreas Körner |
| Institutions | University of Southampton, Schaeffler (Germany) |
| Citations | 17 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Paired Electrosynthesis using MPCVD Diamond
Section titled âTechnical Documentation & Analysis: Paired Electrosynthesis using MPCVD DiamondâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the successful demonstration of a highly efficient, paired electrochemical flow reactor for the simultaneous production of high-value chemicals: Ethylene ($\text{C}_2\text{H}_4$) and Hydrogen Peroxide ($\text{H}_2\text{O}_2$). The system leverages tailored Boron-Doped Diamond (BDD) anodes, a core specialization of 6CCVD.
- Core Achievement: First-ever coupling of 12e- $\text{CO}_2\text{RR}$ (Carbon Dioxide Reduction Reaction) to $\text{C}_2\text{H}_4$ at the cathode with 2e- $\text{WOR}$ (Water Oxidation Reaction) to $\text{H}_2\text{O}_2$ at the anode in an integrated flow cell.
- BDD Anode Performance: Tailored BDD (BDD-a, 12600 ppm B-doping) achieved an unprecedented $\approx 1% \text{ w/w}$ accumulation of $\text{H}_2\text{O}_2$ in $4 \text{ M K}_2\text{CO}_3$ and maintained a stable Faradaic Efficiency (FE) of 60% for 350 hours under single-pass flow conditions at $300 \text{ mA cm}^{-2}$.
- System Efficiency: The paired reactor achieved a combined FE of 120% and a combined Energy Efficiency (EE) of 69% over 50 hours of continuous operation at $200 \text{ mA cm}^{-2}$.
- Economic Impact: The paired system resulted in a 50% decrease in overall Electrical Energy Consumption (EEC) compared to individual electrosynthesis processes, demonstrating significant cost savings and maximized atom economy.
- Material Requirement: The success hinges on the use of highly stable, customized polycrystalline BDD coatings on Niobium substrates, confirming BDD as the most durable anode material for 2e- $\text{WOR}$.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Cathode Material | Mixed Cu Nanowire/Nanoparticle | - | Loaded on Vulcan GDE |
| Anode Material | Boron-Doped Diamond (BDD-a) | - | Deposited on 1 mm Niobium (Nb) plate |
| BDD Doping Level (BDD-a) | 12,600 | ppm | Optimized for 2e- WOR |
| BDD Thickness (BDD-a/b) | 1.6 | ”m | Microcrystalline morphology |
| BDD Facet Size (BDD-a) | 0.47 | nm | Average crystal size |
| Paired Cell Current Density | 200 | $\text{mA cm}^{-2}$ | Continuous operation |
| Paired Cell Voltage | $\approx 5$ | V | Stable over 50 hours |
| $\text{C}_2\text{H}_4$ Faradaic Efficiency (FE) | 60 | % | Cathode performance |
| $\text{H}_2\text{O}_2$ Faradaic Efficiency (FE) | 60 | % | Anode performance |
| Combined FE ($\text{C}_2\text{H}_4 + \text{H}_2\text{O}_2$) | 120 | % | Paired system efficiency |
| Combined Energy Efficiency (EE) | 69 | % | Paired system efficiency |
| Electrical Energy Consumption (EEC) | 11.77 | $\text{kWh kg}^{-1}$ Products | 50% reduction vs. individual processes |
| $\text{H}_2\text{O}_2$ Accumulation (Peak) | $\approx 1$ | % w/w | In $4 \text{ M K}_2\text{CO}_3$ with $8 \text{ g L}^{-1} \text{ Na}_2\text{SiO}_3$ |
| $\text{H}_2\text{O}_2$ Production Rate (Initial) | 135 | $\text{”mol cm}^{-2} \text{ min}^{-1}$ | In $4 \text{ M K}_2\text{CO}_3$ at 9 V |
| $\text{C}_2\text{H}_4$ Stability Test Duration | 370 | hours | Single pass flow |
| $\text{H}_2\text{O}_2$ Stability Test Duration | 350 | hours | Single pass flow |
Key Methodologies
Section titled âKey MethodologiesâThe successful paired electrosynthesis relied on the precise fabrication and optimization of both the cathode and, critically for 6CCVD, the BDD anode.
- BDD Anode Synthesis: Three variants of Boron-Doped Diamond (BDD-a, BDD-b, BDD-c) were synthesized via a custom-built Hot Filament Chemical Vapor Deposition (HF-CVD) apparatus.
- Substrate Preparation: BDD films were deposited onto 1 mm thick Niobium (Nb) plates, chosen for their high conductivity and stability in the flow reactor environment.
- Doping Control: Boron doping levels were precisely adjusted, quantified by Glow Discharge Optical Emission Spectroscopy (GDOES), targeting 12,600 ppm (BDD-a) and $\approx 20,000 \text{ ppm}$ (BDD-b/c).
- Morphological Characterization: SEM, EBSD, and XRD confirmed the BDD films exhibited a microcrystalline, polycrystalline morphology with a predominant occurrence of {111} and {101} facets, essential for high $\text{HO}^{\bullet}$ radical generation.
- Electrolyte Optimization (Anode): The 2e- $\text{WOR}$ was optimized using carbonate-based aqueous electrolytes, with $4 \text{ M K}_2\text{CO}_3$ proving optimal, sometimes supplemented with $\text{Na}_2\text{SiO}_3$ as a peroxy-species stabilizer to hinder $\text{H}_2\text{O}_2$ disproportionation.
- Flow Reactor Operation: The paired system utilized a customized three-compartment flow cell (10 $\text{cm}^2$ active area) operated under single-pass, galvanostatic continuous flow conditions at $200 \text{ mA cm}^{-2}$ total current density.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical role of highly stable, customized Boron-Doped Diamond (BDD) electrodes in enabling high-efficiency paired electrosynthesis. 6CCVD is uniquely positioned to supply and enhance the BDD materials required for replicating and scaling this breakthrough technology.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the high-performance 2e- $\text{WOR}$ achieved in this paper, 6CCVD recommends the following materials:
- Heavy Boron-Doped PCD (Polycrystalline Diamond): The paper utilized BDD with doping levels up to 22,000 ppm. 6CCVD specializes in heavy BDD coatings, ideal for maximizing the $\text{sp}^3/\text{sp}^2$ carbon ratio and promoting the $\text{HO}^{\bullet}$ radical generation pathway necessary for high $\text{H}_2\text{O}_2$ Faradaic Efficiency.
- Custom Substrate Integration: The paper used 1 mm thick Niobium (Nb) plates. 6CCVD routinely deposits BDD films onto various conductive substrates, including Niobium (Nb), Titanium (Ti), and Tungsten (W), with substrate thicknesses up to 10 mm.
- Microcrystalline Morphology Control: The optimal BDD-a exhibited a microcrystalline structure (facet size $\approx 0.47 \text{ nm}$) and specific crystallographic orientation ({111} and {101}). 6CCVD offers precise control over MPCVD growth parameters to tailor BDD morphology, roughness ($\text{R}_a$ < 5nm for inch-size PCD), and crystallite size distribution to match or exceed the performance of BDD-a.
Customization Potential
Section titled âCustomization PotentialâThe success of this flow reactor depends on precise electrode dimensions and integration. 6CCVD offers comprehensive customization services:
| Requirement in Paper | 6CCVD Customization Capability | Value Proposition |
|---|---|---|
| Electrode Area: $10 \text{ cm}^2$ active area (Flow Cell) | Custom Plates/Wafers up to 125 mm (PCD) | Enables rapid scale-up from lab-scale $10 \text{ cm}^2$ to industrial dimensions. |
| BDD Thickness: $1.6 \text{ ”m}$ to $3.1 \text{ ”m}$ | SCD/PCD Thickness range: $0.1 \text{ ”m}$ to $500 \text{ ”m}$ | Precise thickness control for optimizing conductivity and minimizing material cost. |
| Substrate: 1 mm Niobium (Nb) Plate | Custom Substrates (Nb, Ti, W) up to 10 mm thick | Ensures mechanical and chemical compatibility for harsh electrochemical environments. |
| Counter Electrode: Platinized Titanium ($\text{Pt/Ti}$) | Custom Metalization (Au, Pt, Pd, Ti, W, Cu) | 6CCVD can supply the $\text{Pt/Ti}$ counter electrodes or apply custom metal contacts to BDD for enhanced current collection. |
Engineering Support
Section titled âEngineering SupportâThe optimization of BDD doping (12,600 ppm) and morphology for maximizing $\text{HO}^{\bullet}$ radical generation is a complex material science challenge.
6CCVDâs in-house PhD team specializes in the relationship between MPCVD growth parameters, boron incorporation, and electrochemical performance. We can assist researchers and engineers with material selection and optimization for similar Electrochemical $\text{CO}_2$ Reduction (E- $\text{CO}_2\text{RR}$) and Water Oxidation projects, ensuring the BDD material is perfectly matched to the required current density and electrolyte chemistry.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Paired electrolysis offers an auspicious strategy for the generation of highâvalue chemicals, at both the anode and cathode, in an integrated electrochemical reactor. Through efficient electron utilization, routine product misuse at overlooked electrodes can be prevented. Here, an original paired electrosynthetic system is reported that can convert CO 2 to ethylene (C 2 H 4 ) at the cathode, and water to hydrogen peroxide (H 2 O 2 ) at the anode under a single pass of electric charge. Amongst various investigated copper (Cu) nanomorphologies, the bespoke mixed Cu nanowire/nanoparticle catalyst recorded a peak C 2 H 4 Faraday efficiency ( FE ) of 60% following 370 h of electrolysis at 200 mA cm â2 , while the tailored boronâdoped diamond (BDD) anode accumulated an unprecedented â1% w/w of H 2 O 2 in 4 m K 2 CO 3 upon applying 300 mA cm â2 for 10 h. When paired, the dual C 2 H 4 âH 2 O 2 electrochemical cell attains a combined FE of 120% for 50 h at 200 mA cm â2 , a combined energy efficiency (EE) of 69%, and a 50% decrease in the overall electrical energy consumption (EEC) compared to the individual electrosynthesis of C 2 H 4 and H 2 O 2 .