Multifunctional diamond‐based catalysts - Promising candidates for energy conversions in extreme environments—A mini‐review
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2024-07-01 |
| Journal | Electron |
| Authors | Ziwei Zhao, Xiaowu Gao, Hansong Zhang, Keran Jiao, Pengfei Song |
| Institutions | Harbin Institute of Technology, University of Manchester |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Multifunctional Diamond-Based Catalysts for Extreme Environments
Section titled “Technical Documentation & Analysis: Multifunctional Diamond-Based Catalysts for Extreme Environments”Executive Summary
Section titled “Executive Summary”This review highlights the critical role of diamond-based materials in developing robust catalysts for energy conversion (specifically CO$_{2}$RR and photocatalysis) in extreme environments, such as Mars and deep space.
- Extreme Environment Suitability: Diamond’s inherent ultra-wide bandgap (5.5 eV), exceptional thermal conductivity (up to 2200 W/m K), and resistance to high radiation and corrosion make it superior to conventional narrow-bandgap semiconductors and metal catalysts for harsh conditions.
- Electrocatalytic Versatility: Microwave Plasma Chemical Vapor Deposition (MPCVD) diamond, primarily Boron-Doped Diamond (BDD), serves as a highly tunable electrode platform for CO$_{2}$RR.
- Selectivity Control (C$_{1}$): Researchers successfully tuned B doping levels and surface termination (H- vs. O-terminated) to achieve high Faradaic Efficiencies (FE) for C$_{1}$ products, including Formic Acid (HCOOH) (up to 93%) and Carbon Monoxide (CO).
- C$_{2}$+ Production: High-value multi-carbon products (C$_{2}$+), such as Ethanol (FE up to 93.2%) and Acetate, were selectively produced by introducing Nitrogen-Doping (NDD) and synergistic metal co-catalysts (Cu, Pd, Ag).
- Novel Photocatalysis: H-terminated diamond exhibits Negative Electron Affinity (NEA), enabling a unique solvation electron effect for direct reduction of N${2}$ and CO${2}$ without molecular adsorption, overcoming key limitations in traditional photocatalysis.
- Stability Demonstrated: Long-term stability was confirmed, with Cu-NP/NDD electrodes maintaining performance for up to 120 hours of bulk electrolysis, essential for practical space applications.
Technical Specifications
Section titled “Technical Specifications”The following table summarizes key material properties and catalytic performance metrics extracted from the review, demonstrating diamond’s competitive advantage.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Bandgap (Eg) | 5.5 | eV | Ultra-wide bandgap, crucial for radiation resistance. |
| Thermal Conductivity | 2200 | W/m K | Highest among semiconductors, critical for high-power devices. |
| Breakdown Field Strength | 10 | MV/cm | Superior electrical performance. |
| JFOM (Johnson Figure of Merit) | 3064 | 1023 ΩW/s2 | Measures suitability for high-frequency/high-power transistors. |
| BFOM (Baliga Figure of Merit) | 23,017 | (Si = 1) | Measures ability to reduce conduction losses in power devices. |
| HCOOH FE (Maximum) | 93 | % | Achieved using BDD electrode in CsCl electrolyte. |
| CO FE (Maximum) | 82.5 | % | Achieved using Cu-SnOx/BDD composite at -1.6 V vs Ag/AgCl. |
| Ethanol FE (Maximum) | 93.2 | % | Achieved using BNDD (2.5 at.% B, 4.9 at.% N) at -1.0 V vs RHE. |
| C$_{2}$+ Total FE (Maximum) | 89 | % | Achieved using Cu-NP/NDD composite at -0.5 V vs RHE. |
| Long-Term Stability | 120 | hours | Demonstrated stability of Cu-NP/NDD composite during bulk electrolysis. |
Key Methodologies
Section titled “Key Methodologies”The research relies on advanced MPCVD synthesis and post-deposition modification techniques to tailor diamond properties for specific catalytic outcomes.
- Doping Control: Precise control over dopant concentration (Boron and Nitrogen) is used to tune the electronic structure, conductivity, and surface activity of the diamond film, directly impacting product selectivity (C${1}$ vs. C${2}$+).
- Surface Functionalization: Wet chemical, thermal, electrochemical, or plasma treatments are employed to control surface termination (e.g., Hydrogen-terminated for NEA/hydrophobic properties; Oxygen/Carbonyl-terminated for oxidizing/hydrophilic properties).
- Composite Formation via Electrodeposition/Sputtering: Metal nanoparticles (Ag, Pd, Cu) or metal oxides (IrO${2}$, CeO${2}$) are deposited onto the BDD/NDD surface using techniques like cyclic voltammetry (CV) electrodeposition or sputtering to create synergistic catalytic interfaces.
- Polarity Reversal: Electrochemical oxidation/reduction cycles are used to continuously reverse the polarity of BDD electrodes, ensuring long-term stability and recovery of Faradaic Efficiency (FE) for HCOOH production.
- Flow Cell Design: Utilizing flow cell reactors instead of conventional H-type cells to improve mass transport of dissolved CO$_{2}$ to the electrode surface, significantly enhancing production rates (e.g., HCOOH production rate increased to 94.7% FE).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and customization services required to replicate, scale, and extend the research presented in this review for extreme environment applications.
Applicable Materials
Section titled “Applicable Materials”To achieve the high performance and stability demonstrated in the CO$_{2}$RR and photocatalysis studies, 6CCVD recommends the following materials:
- Boron-Doped Diamond (BDD): Essential for high-efficiency C$_{1}$ production (HCOOH, CO) and serving as the foundational conductive electrode material. 6CCVD offers BDD films with precisely controlled doping levels necessary to optimize potential window and suppress competitive Hydrogen Evolution Reaction (HER).
- Custom N-Doped Diamond (NDD/BNDD): Crucial for selective C$_{2}$+ production (Ethanol, Acetate). 6CCVD’s advanced MPCVD capabilities allow for the custom synthesis of Nitrogen-Doped Diamond (NDD) and Boron/Nitrogen Co-Doped Diamond (BNDD) films, enabling the defect-induced active sites required for C-C coupling.
- Optical Grade SCD: For photocatalytic applications leveraging the unique Negative Electron Affinity (NEA) effect, high-purity Single Crystal Diamond (SCD) substrates are available, ensuring maximum optical transparency and structural integrity under high-energy radiation.
Customization Potential
Section titled “Customization Potential”The complexity of diamond-based catalysts requires precise engineering of dimensions, thickness, and surface modification—all core competencies of 6CCVD.
| Research Requirement | 6CCVD Capability | Engineering Advantage |
|---|---|---|
| Large-Area Electrodes | Plates/wafers up to 125mm (PCD) | Enables scaling up from lab-scale H-cells to high-throughput flow cell reactors, addressing the current density limitations noted in the review. |
| Custom Thickness | SCD/PCD films from 0.1µm to 500µm | Allows researchers to optimize film thickness for specific electrochemical or photoelectrochemical device architectures. |
| Metal Co-Catalyst Integration | In-house metalization (Au, Pt, Pd, Ti, W, Cu) | Directly supports the synthesis of high-stability metal/diamond composites (e.g., Pd-NPs/BDD, Cu-NP/NDD) via controlled sputtering or deposition, overcoming stability issues associated with physical trapping. |
| Surface Quality | Polishing to Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD) | Provides the ultra-smooth, controlled surfaces necessary for precise surface functionalization (H- or O-termination) and minimizing sp2 carbon content, which is critical for tuning CO$_{2}$RR selectivity. |
| Substrate Robustness | Substrates up to 10mm thick | Provides robust mechanical and thermal support for catalytic systems operating under the drastic temperature changes and strong impacts of extraterrestrial environments. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in MPCVD growth parameters and material characterization. We offer expert consultation to assist researchers in selecting the optimal diamond material specifications (doping concentration, surface termination, and metalization stack) required for similar CO${2}$ Reduction Reaction (CO${2}$RR) and Photocatalysis in Extreme Environments projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract In order to properly utilize the abundant CO 2 and water resources, various catalytic materials have been developed to convert them into valuable chemicals as renewable fuels electrochemically or photochemically. Currently, most studies are conducted under mild laboratory conditions, but for some extreme environments, such as Mars and space stations, there is an urgent need to develop new catalysts satisfying such special requirements. Conventional catalytic materials mainly focus on metals and narrow bandgap semiconductor materials, while the research on wide and ultrawide bandgap materials that can inherently withstand extreme conditions has not received enough attention. Given the robust stability and excellent physico‐chemical properties of diamond, it can be expected to perform in harsh environments for electrocatalysis or photocatalysis that has not been investigated thoroughly. Here, this review summarizes the catalytic functionality of diamond‐based electrodes with various but tunable product selectivity to obtain the varied C 1 or C 2+ products, and discusses some important factors playing a key role in manipulating the catalytic activity. Moreover, the unique solvation electron effect of diamond gives it a significant advantage in photocatalytic conversions which is also summarized in this mini‐review. In the end, prospects are made for the application of diamond‐based catalysts under various extreme conditions. The challenges that may be faced in practical applications are also summarized and future breakthrough directions are proposed at the end.