| 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 |
- Core Value Proposition: Diamond-based catalysts (Boron-Doped Diamond, BDD; Nitrogen-Doped Diamond, NDD) are promising candidates for energy conversion (CO2 reduction, H2 production) in extreme environments (e.g., Mars, space stations) due to their robust stability, high thermal conductivity (up to 2200 W/mK), and resistance to strong radiation and corrosion.
- Electrocatalytic Tunability: The selectivity of CO2 reduction reaction (CO2RR) products is highly tunable by controlling doping (B, N content), carbon hybridization (sp2/sp3 ratio), and surface termination (H- or O-groups).
- C2+ Product Achievement: B/N co-doped nanodiamonds (BNDDs) demonstrated exceptional C-C coupling capability, achieving a maximum Faradaic Efficiency (FE) of 93.2% for ethanol (C2+ product) at -1.0 V vs. RHE, significantly surpassing conventional BDD performance.
- Mass Transport Optimization: Utilizing flow cells and intermittent electrolyte flow dramatically improved mass transport, enabling stable and highly efficient production of formic acid (HCOOH), reaching up to 94.7% FE.
- Photocatalytic Mechanism: H-terminated diamond exhibits a unique Negative Electron Affinity (NEA), allowing direct emission of solvated electrons into the reaction solution. This mechanism provides high reduction power (redox potential of -1.9 V vs. SHE) without requiring molecular adsorption, overcoming limitations in reactions like N2 reduction.
- Enhanced Stability: Metal nanoparticle composites (e.g., Cu-NP/NDD) showed synergistic effects, stabilizing the metal phase and preventing particle aggregation, resulting in long-term durability (120 h bulk electrolysis with only 19% activity decline).
| Parameter | Value | Unit | Context |
|---|
| Bandgap (Diamond) | 5.5 | eV | Intrinsic property (Ultra-wide bandgap) |
| Thermal Conductivity (Diamond) | 2200 | W/mK | Intrinsic property (Highest among competitors) |
| Breakdown Field Strength (Diamond) | 10 | MV/cm | Intrinsic property |
| Ethanol FE (BNDD) | 93.2 | % | CO2RR at -1.0 V vs. RHE (C2+ selectivity) |
| HCOOH FE (Flow Cell, BDD) | 94.7 | % | Optimized mass transport conditions |
| HCOOH FE (BDD, CsCl electrolyte) | 93 | % | Alkali metal cation effect (Cs+ suppresses HER) |
| CO FE (Cu-SnOx/BDD) | 82.5 | % | CO2RR at -1.6 V vs. Ag/AgCl |
| CO FE (Ag-NPs/BDD) | 68 | % | CO2RR at -1.8 V vs. Ag/AgCl |
| NDD Onset Potential (CO2 reduction) | -0.36 | V | vs. RHE |
| Solvated Electron Redox Potential | -1.9 | V | vs. SHE |
| BDD/Cu-NP Stability | 120 | h | Bulk electrolysis duration |
| Activity Decline (BDD/Cu-NP) | 19 | % | Decline over 120 h electrolysis |
| Martian Atmospheric CO2 Content | 95.32 | % | Primary resource for ISRU |
| Lunar Solar Energy Intensity | >6 | Times Earth’s | Energy source for photocatalysis |
- Diamond Synthesis and Doping: Diamond materials (BDD, NDD, BNDD) are synthesized artificially, often using Microwave Plasma Chemical Vapor Deposition (MPCVD), allowing precise control over B and N doping concentrations and the resulting electronic structure.
- Surface Termination Control: Surface properties are modified using wet chemical, thermal, electrochemical, or plasma treatments to control termination (e.g., hydrogen-terminated for Negative Electron Affinity, NEA; oxygen-terminated for Positive Electron Affinity, PEA).
- Composite Catalyst Fabrication: Metal nanoparticles (Cu, Ag, Pd) or metal oxides (IrO2, CeO2) are loaded onto BDD/NDD substrates via electrodeposition or immersion in colloidal solutions to create synergistic catalytic interfaces and enhance activity/selectivity.
- Electrochemical Reactor Design: Standard H-type electrolytic cells are used for conventional testing, while advanced flow cells are employed to improve mass transport of dissolved CO2, leading to higher current densities and production rates.
- Electrolyte and Flow Optimization: Catalytic performance is optimized by varying electrolyte composition (cation type, anion type, concentration) and controlling the flow rate, including the use of intermittent flow systems to maximize intermediate adsorption time.
- In Situ Characterization: Techniques like Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy are used in situ to monitor the adsorption and reaction pathways of CO2 intermediates on the diamond electrode surface.
- Photocatalytic Activation: H-terminated diamond is irradiated with UV light (e.g., 213 nm) to leverage the NEA effect, resulting in the direct emission of highly reductive solvated electrons into the aqueous solution for reactions like N2 or CO2 reduction.
- In-Situ Resource Utilization (ISRU) for Space Exploration: Direct application for converting abundant Martian CO2 and water ice into methane (CH4), oxygen (O2), and water (H2O) using Sabatier/electrolysis reactions driven by solar energy or electricity.
- High-Stability Chemical Manufacturing: Use of diamond electrodes in industrial electrochemical reactors requiring extreme stability against highly corrosive (acid/alkali) or high-temperature environments where conventional metal catalysts rapidly deactivate.
- Sustainable Fuel and Chemical Production: Highly selective electrocatalytic conversion of CO2 into valuable C1 products (HCOOH, CO) and C2+ liquid fuels (ethanol, acetate), supporting carbon-neutral energy cycles.
- Advanced Water Treatment: Leveraging the wide potential window and anti-fouling properties of BDD electrodes for robust electrochemical degradation of persistent organic pollutants in industrial wastewater.
- Radiation-Hardened Power Electronics: Utilizing the superior electronic properties (high breakdown field, high mobility) and radiation resistance of diamond for high-power, high-frequency transistors and devices operating in harsh radiation fields.
- Hydrogen Energy Systems: Application of nanodiamond composites in photocatalytic water splitting for efficient, solar-driven hydrogen (H2) production, a key component of renewable energy infrastructure.
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.