2D Hexagonal Boron Nitride (2D‐hBN) Explored as a Potential Electrocatalyst for the Oxygen Reduction Reaction
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2016-09-28 |
| Journal | Electroanalysis |
| Authors | Aamar F. Khan, Edward P. Randviir, Dale A. C. Brownson, Xiaobo Ji, Graham C. Smith |
| Institutions | Central South University, University of Chester |
| Citations | 55 |
| Analysis | Full AI Review Included |
Technical Analysis and Material Sourcing Documentation: 2D-hBN Electrocatalysis for ORR
Section titled “Technical Analysis and Material Sourcing Documentation: 2D-hBN Electrocatalysis for ORR”Executive Summary
Section titled “Executive Summary”The attached research explores Crystalline 2D Hexagonal Boron Nitride (2D-hBN) as a potential metal-free electrocatalyst for the Oxygen Reduction Reaction (ORR) in acidic media (0.1 M H₂SO₄). The findings highlight critical dependencies on substrate morphology and material loading, validating the need for precise substrate engineering in 2D nanomaterial integration.
- ORR Performance: 2D-hBN successfully improved ORR performance only when immobilized on rough carbon substrates (Screen-Printed Graphite Electrodes, SPEs).
- Peak Potential Reduction: The optimal configuration (324 ng 2D-hBN/SPE) achieved a significant reduction in the ORR activation potential of ca. 0.28 V compared to bare SPEs.
- Substrate Dependency: The electrocatalytic benefit was lost or reversed on smooth substrates, including Glassy Carbon (GC) and Boron-Doped Diamond (BDD), confirming that 2D-hBN requires ridged surfaces to expose active edge sites.
- Mechanistic Limitation: Tafel analysis confirmed the ORR proceeds primarily via an unfavorable 2-electron pathway (n=1.90-2.45), generating hydrogen peroxide (H₂O₂) rather than the desired 4-electron pathway necessary for high-efficiency PEM fuel cells.
- Key Material Insight: This work demonstrates that surface roughness (measured by Root Mean Squared, SQ) is a dominant, often overlooked, parameter governing the successful “electrical wiring” of 2D nanomaterials.
- 6CCVD Relevance: While 2D-hBN showed no catalytic benefit on BDD in this study, the requirement for precisely controlled surface morphology confirms 6CCVD’s expertise in providing highly characterized and customizable SCD and BDD substrates for next-generation electrochemistry research.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research paper regarding material properties and electrochemical performance metrics:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal ORR Potential Shift | 0.28 | V | 324 ng 2D-hBN on SPE vs. bare SPE (100 mVs-1) |
| Best ORR Potential (2D-hBN/SPE) | -0.81 | V | 324 ng 2D-hBN on SPE (100 mVs-1 vs. SCE) |
| ORR Electron Transfer (n) Range | 1.90 - 2.45 | N/A | Calculated for 108-324 ng 2D-hBN on SPEs (2-electron mechanism) |
| 2D-hBN Lateral Particle Size (Avg) | ca. 200 | nm | Commercially sourced pristine flakes |
| 2D-hBN Flake Thickness | 2 - 4 | Layers | Estimated layers immobilized on silicon wafer |
| Electrolyte | 0.1 M | H₂SO₄ | ORR testing medium (acidic) |
| Assumed Oxygen Concentration | 0.9 | mM | Used for H₂O₂ yield calculations |
| Roughness Factor (RF) (Bare SPE) | 1.0 | N/A | Calculated via double layer capacitance |
| Roughness Factor (RF) (324 ng hBN/SPE) | 49.9 | N/A | Significant increase due to 2D-hBN adherence |
| Surface Roughness (SQ) (Unpolished SPE) | 1338.8 | nm | Root Mean Squared value before modification |
| Surface Roughness (SQ) Increase (Unpolished SPE) | 414.1 | nm | Resulting from 108 ng 2D-hBN drop-casting |
| HET Rate Constant (keff) (Bare SPE) | 3.05 x 10-3 | cm s-1 | Unmodified SPE (Ru(NH3)62+/3+ probe) |
| HET Rate Constant (keff) (324 ng hBN/SPE) | 1.09 x 10-3 | cm s-1 | Electron transfer kinetics decreased with hBN mass |
Key Methodologies
Section titled “Key Methodologies”The experimental procedure focused on substrate comparison and precise coverage control of the 2D-hBN nanomaterial:
- Substrate Preparation: Six different working electrodes were utilized, including Screen-Printed Graphite Electrodes (SPEs), Glassy Carbon (GC), Boron-Doped Diamond (BDD), Edge-Plane Pyrolytic Graphite (EPPG), Platinum (Pt), and Gold (Au). Non-SPE electrodes were polished using 1.00 µm and 0.25 µm diamond spray prior to modification.
- 2D-hBN Suspension: Pristine 2D-hBN nanoscale crystals (>99% purity, 5.4 mg L-1) were dispersed in ethanol via liquid exfoliation.
- Immobilization Technique: Measured aliquots of the 2D-hBN suspension (ranging from 10.8 ng to 324 ng) were applied to the working electrodes via drop-casting using a micropipette.
- Drying Process: Electrodes were allowed to dry at ambient temperature for 30 minutes to ensure complete ethanol evaporation.
- Electrochemical Testing: Cyclic Voltammetry (CV) was conducted in a three-electrode system using an external Saturated Calomel Electrode (SCE) as reference and a Platinum (Pt) wire as the counter electrode.
- ORR Conditions: ORR tests were performed in oxygen-saturated 0.1 M H₂SO₄ (Sulfuric Acid). Scan rates ranged from 10 mVs-1 to 400 mVs-1.
- Physical Analysis: SEM and White Light Profilometry were used to measure the change in surface roughness (SQ) and Roughness Factor (RF), establishing that hBN preferentially adhered to ridged (rough) surfaces.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research reinforces a core principle of advanced electrochemistry: material integration and surface morphology are inseparable from device performance. 6CCVD is uniquely positioned to address the stringent substrate requirements needed to replicate and advance this research, particularly involving diamond materials.
Applicable Materials
Section titled “Applicable Materials”The paper critically tested Boron-Doped Diamond (BDD) substrates. While the study found 2D-hBN failed to exhibit an ORR peak on BDD, the diamond substrate remains an ideal inert, high-potential window platform for catalyst testing.
- Boron-Doped Diamond (BDD): 6CCVD provides high-quality MPCVD BDD plates and wafers. BDD is essential for baseline comparisons and systems requiring extremely stable, high-potential substrates, offering superior performance to the GC and SPE substrates utilized.
- Single Crystal Diamond (SCD): For high-precision applications, 6CCVD supplies Optical Grade SCD material (SCD up to 500 µm thickness) which can serve as an exceptionally low-noise, smooth platform (Ra < 1 nm) for studies aiming to test the hBN smoothness dependency explicitly.
Customization Potential: Engineering Surface Morphology
Section titled “Customization Potential: Engineering Surface Morphology”The primary takeaway of the paper is that surface roughness (specifically SQ values > 1300 nm) is key for successful 2D-hBN adherence and activation. 6CCVD can intentionally engineer substrates to meet these specific morphological demands.
| Research Requirement | 6CCVD Engineering Solution | Capability Alignment |
|---|---|---|
| Controlled Roughness | Supply of MPCVD diamond with defined, controlled post-growth surface finishes (unpolished or semi-polished) to maximize ridged/edge sites, essential for 2D-hBN “electrical wiring.” | Custom Polishing (or omission thereof) up to Ra < 1 nm (SCD) or Ra < 5 nm (PCD). |
| Custom Dimensions | Delivery of BDD or SCD wafers up to 125 mm, allowing researchers to rapidly scale up successful lab-bench experiments to commercial-scale testing. | Wafers up to 125 mm (PCD/BDD). |
| Integrated Contacts | The study compared results to Au and Pt electrodes. 6CCVD offers seamless, in-house metalization services for integrating electrical contacts onto the diamond substrate surface (e.g., Ti/Pt/Au contact pads) prior to catalyst application. | Internal Metalization (Au, Pt, Pd, Ti, W, Cu). |
| Custom Thickness/Doping | Provision of BDD layers with customizable boron concentration and thickness (0.1 µm - 500 µm) to study how BDD electronic properties interact with 2D-hBN integration. | SCD/PCD/BDD thickness control (0.1 µm - 500 µm). |
Engineering Support & Logistics
Section titled “Engineering Support & Logistics”6CCVD provides comprehensive technical support to ensure successful project implementation, from material selection to delivery:
- Application Expertise: 6CCVD’s in-house PhD engineering team can assist researchers in material selection, optimization of doping levels, and surface preparation protocols for Fuel Cell Electrocatalysis and ORR projects, leveraging deep knowledge of BDD and SCD capabilities.
- Global Supply Chain: We ensure reliable delivery of custom diamond materials worldwide, simplifying logistics for international collaborators working on advanced energy devices. (DDU default, DDP available).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Crystalline 2D hexagonal Boron Nitride (2D‐hBN) is explored as a potential electrocatalyst towards the oxygen reduction reaction (ORR) when electrically wired via a drop‐casting approach upon a range of carbon based electrode surfaces; namely, glassy carbon (GC), boron‐doped diamond (BDD), and screen‐printed graphitic electrodes (SPEs). We consider the ORR in acidic conditions and critically evaluate the performance of unmodified and 2D‐hBN modified electrodes, implementing coverage studies (commonly neglected in the literature) in order to ascertain the true impact of this novel nanomaterial. The behaviour of 2D‐hBN towards the ORR is shown to be highly dependent upon both the underlying carbon substrate and the coverage/mass utilised. 2D‐hBN modified SPEs are found to exhibit the most beneficial response towards the ORR, reducing the peak potential by ca . 0.28 V when compared to an unmodified/bare SPE. Such improvements at this supporting substrate are inferred due to favourable 2D‐hBN interaction with ridged surfaces exposing a high proportion of edge regions/sites, where conversely, we show that relatively smooth substrate surfaces (such as GC) are less conducive towards successful 2D‐hBN immobilisation. In this paper, we reveal for the first time (in the specific case of using a rough supporting substrate) that 2D‐hBN gives rise to beneficial electrochemical behaviour towards the ORR. Unfortunately, this material is not considered an electrocatalyst for use within fuel cells given that the estimated number of electrons transferred during the ORR ranges between 1.90-2.45 for different coverages, indicating that the ORR at 2D‐hBN predominantly produces hydrogen peroxide. 2D‐hBN does however have potential and should be explored further by those designing, fabricating and consequently electrochemically testing modified electrocatalysts towards the ORR.