Iron Active Center Coordination Reconstruction in Iron Carbide Modified on Porous Carbon for Superior Overall Water Splitting
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-04-24 |
| Journal | Advanced Science |
| Authors | Wenxin Guo, Jinlong Li, DongâFeng Chai, Dongxuan Guo, Guozhe Sui |
| Institutions | Qiqihar University, University of Waterloo |
| Citations | 31 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Iron Carbide Electrocatalysts on Carbon Substrates
Section titled âTechnical Documentation & Analysis: Iron Carbide Electrocatalysts on Carbon SubstratesâExecutive Summary
Section titled âExecutive SummaryâThis research details a highly effective strategy for creating non-precious metal electrocatalysts for overall water splitting (OWS) using iron carbide (Fe$_{3}$C) supported on nitrogen-doped porous carbon (NC).
- Novel Synthesis: A liquid nitrogen quenching (LNQ) strategy was engineered to induce active center coordination reconstruction within the Fe$_{3}$C/NC catalyst.
- Superior Performance: The optimized catalyst (Fe$_{3}$C/NC-550) achieved outstanding OWS activity, requiring only 1.57 V to drive 10 mA cm-2 in alkaline media.
- Ultra-Low Overpotentials: The catalyst demonstrated exceptional performance for both half-reactions: 26.3 mV for the Hydrogen Evolution Reaction (HER) and 281.4 mV for the Oxygen Evolution Reaction (OER) at 10 mA cm-2.
- Kinetic Enhancement: LNQ induced phase transformation (Cohenite to Iron Carbide) and created rich carbon vacancies, resulting in the lowest Tafel slopes (83.3 mV dec-1 for HER) among tested samples.
- Mechanism Verified: Density Functional Theory (DFT) calculations confirmed that the coordination reconstruction optimizes the adsorption free energy of reaction intermediates ($\Delta G_{H*}$), enhancing intrinsic electrocatalytic activity.
- Stability: The Fe$_{3}$C/NC-550 catalyst maintained stability for 168 hours during continuous HER operation.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the analysis of the Fe$_{3}$C/NC-550 electrocatalyst performance in 1.0 M KOH.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal Quenching Temperature | 550 | °C | For Fe$_{3}$C/NC-550 catalyst synthesis |
| HER Overpotential ($\eta$) | 26.3 | mV | At -10 mA cm-2 current density |
| OER Overpotential ($\eta$) | 281.4 | mV | At 10 mA cm-2 current density |
| Overall Water Splitting Voltage | 1.57 | V | At 10 mA cm-2 current density |
| HER Tafel Slope | 83.3 | mV dec-1 | Lowest value, indicating fastest HER kinetics |
| OER Tafel Slope | 127.0 | mV dec-1 | Indicating beneficial OER reaction kinetics |
| Specific Surface Area (BET) | 319.9 | m2 g-1 | For Fe$_{3}$C/NC-550 sample |
| Cooling Rate (Ultrahigh) | 246 - 946 | °C s-1 | Generated by liquid nitrogen quenching |
| Optimized $\Delta G_{H*}$ | 0.21 | eV | Near ideal 0 eV for HER activity (DFT) |
| Electrolyte Concentration | 1.0 | M | KOH (Alkaline medium) |
Key Methodologies
Section titled âKey MethodologiesâThe synthesis of the highly active Fe$_{3}$C/NC-550 electrocatalyst relies on a precise thermal treatment followed by rapid quenching.
- Precursor Preparation: Biomass (chrysanthemum tea) was immersed in an aqueous solution containing the iron precursor, C${6}$H${5}$FeO$_{7}$.
- High-Temperature Pyrolysis: The dried precursor was subjected to thermal treatment at 750 °C for 10 minutes in a horizontal tube furnace under a continuous flow of mixed hydrogen and argon gases. This step forms the initial Fe$_{3}$C/NC structure (Cohenite phase).
- Liquid Nitrogen Quenching (LNQ): Immediately after calcination, the Fe$_{3}$C/NC nanosheets, while at a surface high-temperature (optimized at 550 °C), were rapidly quenched in liquid nitrogen (-196 °C).
- Coordination Reconstruction: The ultrahigh cooling rate generated a strong resultant force, inducing a phase transformation from Cohenite (PDF#97-001-6593) to Iron Carbide (PDF#97-016-7667) and creating carbon vacancies.
- Characterization: The resulting materials were analyzed using X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR), and X-ray Absorption Fine Structure (EXAFS) to verify the Fe active center coordination reconstruction and electronic structure changes.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical role of highly conductive, stable carbon supports in achieving high-efficiency electrocatalysis. While the paper utilizes biomass-derived porous carbon, 6CCVD offers superior diamond materials that provide the ultimate platform for scaling up and stabilizing next-generation green energy conversion systems.
Applicable Materials for Electrocatalysis
Section titled âApplicable Materials for ElectrocatalysisâTo replicate or extend this high-performance water splitting research, 6CCVD recommends leveraging the unparalleled stability and conductivity of our MPCVD diamond materials:
- Heavy Boron-Doped Diamond (BDD): BDD is the gold standard for stable electrochemical platforms. It offers a wider potential window and superior corrosion resistance compared to traditional carbon supports (like the porous carbon used in the paper), ensuring long-term stability far exceeding the 168 hours demonstrated.
- Polycrystalline Diamond (PCD) Wafers: For industrial scaling of OWS/HER/OER devices, 6CCVD provides large-area PCD wafers up to 125mm in diameter, offering highly uniform and robust electrode substrates.
- Single Crystal Diamond (SCD) Substrates: For fundamental research requiring precise control over surface termination and defect density, our SCD material provides exceptional purity and structural integrity.
Customization Potential for Advanced Integration
Section titled âCustomization Potential for Advanced IntegrationâThe integration of transition metal carbides (like Fe$_{3}$C) onto a diamond electrode requires specialized material preparation and interface engineering, which 6CCVD provides in-house.
| Capability | Specification | Relevance to Fe$_{3}$C/NC Research |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125mm (PCD). Substrates up to 10mm thick. | Ideal for manufacturing large-scale, high-surface-area electrodes for alkaline electrolyzers. |
| Metalization Services | In-house deposition of Au, Pt, Pd, Ti, W, Cu. | Essential for creating robust ohmic contacts or adhesion layers (e.g., Ti/Pt/Au) necessary to anchor the Fe$_{3}$C nanoparticles onto the diamond substrate. |
| Precision Polishing | Ra < 1nm (SCD), Ra < 5nm (Inch-size PCD). | Crucial for surface-sensitive studies (XPS, EXAFS) to ensure consistent, defect-controlled surfaces for catalyst deposition and analysis. |
| Thickness Control | SCD/PCD layers from 0.1”m to 500”m. | Allows engineers to tailor the diamond layer thickness based on specific electrical resistance and thermal management requirements of the electrolyzer cell. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD material science team specializes in optimizing diamond properties for demanding electrochemical applications. We can assist researchers in selecting the optimal BDD doping level and surface termination to maximize charge transfer efficiency and stability for similar overall water splitting projects, ensuring the highest performance and longevity for your next-generation electrocatalysts.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract In this work, a novel liquid nitrogen quenching strategy is engineered to fulfill iron active center coordination reconstruction within iron carbide (Fe 3 C) modified on biomassâderived nitrogenâdoped porous carbon (NC) for initiating rapid hydrogen and oxygen evolution, where the chrysanthemum tea (elm seeds, corn leaves, and shaddock peel, etc.) is treated as biomass carbon source within Fe 3 C and NC. Moreover, the original thermodynamic stability is changed through the corresponding force generated by liquid nitrogen quenching and the phase transformation is induced with rich carbon vacancies with the increasing instantaneous temperature drop amplitude. Noteworthy, the optimizing intermediate absorption/desorption is achieved by new phases, Fe coordination, and carbon vacancies. The Fe 3 C/NCâ550 (550 refers to quenching temperature) demonstrates outstanding overpotential for hydrogen evolution reaction (26.3 mV at â10 mA cm â2 ) and oxygen evolution reaction (281.4 mV at 10 mA cm â2 ), favorable overall water splitting activity (1.57 V at 10 mA cm â2 ). Density functional theory (DFT) calculations further confirm that liquid nitrogen quenching treatment can enhance the intrinsic electrocatalytic activity efficiently by optimizing the adsorption free energy of reaction intermediates. Overall, the above results authenticate that liquid nitrogen quenching strategy open up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.