Catalytic Electrochemical Water Splitting Using Boron Doped Diamond (BDD) Electrodes as a Promising Energy Resource and Storage Solution

At a Glance

Metadata	Details
Publication Date	2020-10-10
Journal	Energies
Authors	Yousef Al-Abdallat, Inshad Jumah, Rami Jumah, Hanadi Ghanem, Ahmad Telfah
Institutions	Kirchhoff (Germany), German Jordanian University
Citations	8
Analysis	Full AI Review Included

Executive Summary

This study investigates the use of Boron Doped Diamond (BDD) electrodes on Niobium (Nb) mesh substrates for catalytic electrochemical water splitting, focusing on energy efficiency and dissipation reduction using metal oxide nanoparticles (NPs).

Core Technology: A novel electrochemical reactor utilizing BDD/Nb mesh electrodes synthesized via Hot Filament Chemical Vapor Deposition (HFCVD) for efficient water splitting.
Catalyst Performance: Copper Oxide (CuO) NPs demonstrated superior catalytic performance compared to Zinc Oxide (ZnO) NPs and the non-catalyzed buffer system.
Energy Efficiency Gain: The overall energy efficiency was dramatically improved from 25% (non-catalyzed) to 100% (normalized, using CuO NPs), representing the highest magnitude of splitting energy.
Dissipation Reduction: Catalysis significantly reduced thermal energy dissipation. Normalized dissipation was 1.0 (non-catalyzed), reduced to 0.65 (CuO NPs) and 0.48 (ZnO NPs).
Electrode Stability: BDD/Nb electrodes provide high chemical resistance and stability, crucial for long-term operation under high voltage conditions.
Mechanism Insight: Catalyzed systems exhibit stable electrical current and voltage, suggesting facilitated ionic charge transportation and attenuation of solution polarization by the NPs.
Application Potential: The system is proposed for solar-powered hydrogen production, suitable for use in Proton Exchange Membrane Fuel Cells (PEMFCs) and Direct Methanol Fuel Cells (DMFCs).

Technical Specifications

Parameter	Value	Unit	Context
Electrode Substrate	Niobium (Nb) Mesh	N/A	Mesh type C1_METAKEM GmbH
BDD Film Thickness	8	µm	Deposited via HFCVD
BDD Deposition Pressure	7	mbar	HFCVD process condition
BDD Dopant	Trimethyl borate (B(OCH₃)₃)	N/A	Boron source for conductivity
Crystalline BDD Peak	1337	cm^-1	Raman spectroscopy result
Preferred Orientation	(111) facet	N/A	XRD analysis (2θ = 43.9°)
Electrode Surface Area	63	cm²	Geometrical area of mesh electrodes
Electrode Spacing	1	mm	Distance between anode and cathode
Applied Voltage (V_av)	15.60 - 15.62	V	Stable DC input across all systems
Initial Solution pH	6.5	N/A	Water buffer solution
Initial Conductivity (σ)	140 - 160	µS/cm	Initial buffer solution range
Catalyst Concentration	10	mg/L	CuO NPs and ZnO NPs
Non-Catalyzed Efficiency	25	%	Overall efficiency (H₂O buffer)
Normalized Efficiency (ZnO)	82	%	Relative to CuO NPs (100%)
Normalized Dissipation (CuO)	0.65	a.u.	Relative to Non-Catalyzed (1.0)
Normalized Dissipation (ZnO)	0.48	a.u.	Relative to Non-Catalyzed (1.0)

Key Methodologies

The BDD/Nb electrodes were fabricated and tested in a 2 L Plexiglas reactor under controlled conditions to assess electrochemical water splitting performance.

Substrate Preparation: Niobium (Nb) mesh was mechanically pre-treated using particle blasting to enhance surface roughness and adhesion.
Seeding: The treated Nb mesh was ultrasonically cleaned with ethanol, followed by seeding using nano diamond dispersion via an ultrasonic nucleation process.
BDD Coating (HFCVD): BDD film (8 µm thickness) was deposited using Hot Filament Chemical Vapor Deposition (HFCVD) at low pressure (7 mbar) in a CH₄/H₂ atmosphere, activated by a resistively heated tungsten filament.
Boron Doping: Trimethyl borate (B(OCH₃)₃) was incorporated into the gaseous mixture to achieve boron doping, enhancing electrical conductivity.
Electrochemical Setup: Two BDD/Nb mesh electrodes (63 cm² area, 1 mm spacing) were connected to a DC power supply (Gwisntek GPC 30300) providing a stable voltage (~15.6 V).
Catalysis Testing: Experiments were run using three systems: non-catalyzed water buffer (pH 6.5), catalyzed with CuO NPs (10 mg/L), and catalyzed with ZnO NPs (10 mg/L).
Data Monitoring: Electrical current (I), voltage (V), conductivity (σ), acidity (pH), and temperature (T) were monitored simultaneously over time.
Energy Calculation: Input energy (E_input) was calculated by integrating V(t)I(t)dt. Dissipated energy (E_diss) was calculated based on the thermal energy absorbed by the solution, glass beaker, and electrodes. Splitting energy (E_split) was determined by subtracting E_diss and evaporation energy (E_evap) from E_input.

Commercial Applications

The development of highly efficient, stable BDD/Nb electrodes for catalytic water splitting directly supports several high-value energy and environmental sectors.

Hydrogen Economy & Energy Storage:
- Hydrogen Fuel Production: Efficiently generating hydrogen gas (H₂) from water using solar power as the primary energy input.
- Fuel Cells: Supplying H₂ directly to hydrogen internal combustion engines or Proton Exchange Membrane Fuel Cells (PEMFCs).
- Methanol Synthesis: Indirectly producing methanol (via CO₂ hydrogenation) for use in Direct Methanol Fuel Cells (DMFCs).
Electrochemical Processing:
- Wastewater Treatment: Utilizing the BDD anode’s high oxidation potential for simultaneous wastewater treatment and hydrogen production, reducing overall operational costs.
- High-Efficiency Electrolysis: Applicable in industrial electrolyzers requiring stable, high-voltage electrodes with minimal kinetic overpotentials.
Advanced Materials & Catalysis:
- BDD Electrode Manufacturing: Scaling up HFCVD techniques for producing large-area, high-quality BDD films on conductive substrates like Niobium for industrial applications.
- Nanoparticle Integration: Developing stable, high-surface-area metal oxide NP catalysts (like CuO) optimized for integration into electrochemical systems to boost efficiency.

View Original Abstract

The present study developed a new system of electrochemical water splitting using a boron doped diamond (BDD) electrode in the electrochemical reactor. The new method assessed the electrical current, acidity (pH), electrical conductivity, absorbance, dissipation, and splitting energies in addition to the water splitting efficiency of the overall process. Employing CuO NPs and ZnO NPs as catalysts induced a significant impact in reducing the dissipated energy and in increasing the efficiency of splitting water. Specifically, CuO NPs showed a significant enhancement in reducing the dissipated energy and in keeping the electrical current of the reaction stable. Meanwhile, the system catalyzed with ZnO NPs induced a similar impact as that for CuO NPs at a lower rate only. The energy dissipation rates in the system were found to be 48% and 65% by using CuO and ZnO NPs, respectively. However, the dissipation rate for the normalized system without catalysis (water buffer at pH = 6.5) is known to be 100%. The energy efficiency of the system was found to be 25% without catalysis, while it was found to be 82% for the system catalyzed with ZnO NPs compared to that for CuO NPs (normalized to 100%). The energy dissipated in the case of the non-catalyzed system was found to be the highest. Overall, water splitting catalyzed with CuO NPs exhibits the best performance under the applied experimental conditions by using the BDD/Niobium (Nb) electrodes.

Tech Support

Original Source

DOI: https://doi.org/10.3390/en13205265

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