Porous BiVO4/Boron-Doped Diamond Heterojunction Photoanode with Enhanced Photoelectrochemical Activity

At a Glance

Metadata	Details
Publication Date	2022-08-16
Journal	Molecules
Authors	Jiangtao Huang, Aiyun Meng, Zongyan Zhang, Guanjie Ma, Yuhao Long
Institutions	Shenzhen University, Shenzhen Technology University
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Porous BiVO4/Boron-Doped Diamond Heterojunction Photoanode

6CCVD Internal Document Reference: PEC-BDD-BiVO4-2022

Executive Summary

This research successfully demonstrates a high-performance photoelectrochemical (PEC) photoanode utilizing a novel porous n-type Bismuth Vanadate (BiVO$_{4}$) film grown on a p-type Boron-Doped Diamond (BDD) substrate. The BDD material supplied the necessary robustness and electrical properties for the heterojunction.

Core Achievement: Fabrication of a porous BiVO$_{4}$/BDD p-n heterojunction, leveraging BDD’s chemical robustness and high conductivity for enhanced PEC activity.
Optimal Performance: The optimized photoanode (M30, 30 min BiVO${4}$ deposition) achieved a peak current density of 1.8 mA/cm² at 1.23 V${RHE}$ under AM 1.5 irradiation.
Environmental Application: Demonstrated high efficiency in organic pollutant degradation, achieving a 45.1% removal of tetracycline hydrochloride (TCH) in 10 minutes.
Mechanism of Enhancement: The superior PEC performance is attributed to the formation of masses of ultra-micro p-n heterojunction electrodes and porous BiVO$_{4}$ structures, which significantly boost charge transport efficiency and reduce carrier recombination.
Material Synthesis: BDD films were prepared via Hot Filament Chemical Vapor Deposition (HFCVD) on conductive silicon (Si) substrates, followed by BiVO$_{4}$ deposition via Magnetron Sputtering (MS).
Material Role: The p-type BDD acts as a stable, hole-rich electrode, driving the migration of photogenerated electrons from the n-type BiVO$_{4}$ and facilitating the oxidation reaction.

Technical Specifications

The following hard data points were extracted from the analysis of the optimized M30 BiVO$_{4}$/BDD photoanode:

Parameter	Value	Unit	Context
Peak Current Density (J)	1.8	mA/cm²	M30 sample, at 1.23 V_RHE, AM 1.5
TCH Degradation Rate (k)	0.057	min^-1	Highest first-order kinetic rate constant
TCH Removal Efficiency	45.1	%	M30 sample, 10 minutes
BiVO$_{4}$ Band Gap (E_g)	2.5 ± 0.1	eV	Determined via Tauc plot
*BiVO${4}$ Carrier Density (N${D}$)*	10¹⁸	cm^-3	Calculated from Mott-Schottky plots
BDD Carrier Density (N$_{A}$)	10¹⁸	cm^-3	Calculated from Mott-Schottky plots
BDD Raman Shift	1331	cm^-1	Characteristic peak of crystalline diamond
*Optimized BiVO${4}$ Deposition Time (T${d}$)*	30	min	Parameter for M30 sample
Annealing Temperature	500	°C	Post-sputtering thermal treatment

Key Methodologies

The fabrication of the porous BiVO$_{4}$/BDD heterojunction photoanodes involved precise control over the deposition and post-treatment processes:

BDD Substrate Preparation: Conductive silicon (Si) substrates were seeded with diamond nanoparticles to facilitate subsequent growth.
BDD Film Growth (HFCVD): p-type BDD films were deposited using Hot Filament Chemical Vapor Deposition (HFCVD) in a gas mixture of Methane (CH${4}$), Hydrogen (H${2}$), and Trimethyl Borane (TMB).
V-BiVO$_{4}$ Deposition (MS): An amorphous V-rich BiVO${4}$ film was deposited on the BDD surface using a Magnetron Sputtering (MS) system. The targets were Vanadium (V) and BiVO${4}$, sputtered in an O$_{2}$/Ar gas mixture.
Thickness Control: The thickness of the V-BiVO${4}$ film, which dictates the ultra-micro electrode formation, was controlled by tuning the sputtering duration (T${d}$), ranging from 15 min (M15) to 75 min (M75).
Vanadium Solution Treatment: A vanadium (V) solution (vanadyl acetylacetonate in DMSO) was dropwise added to the V-BiVO$_{4}$/BDD composite films.
Crystallization Annealing: The films were annealed at 500 °C for 120 minutes under atmospheric conditions to crystallize the BiVO$_{4}$ phase.
Porous Structure Formation: Excess V${2}$O${5}$ was removed using a 1 M NaOH solution, successfully synthesizing the final porous BiVO$_{4}$/BDD heterojunction photoanodes.

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality, highly conductive Boron-Doped Diamond (BDD) substrates in advanced photoelectrochemical systems. 6CCVD is uniquely positioned to supply the necessary diamond materials and customization services to replicate, scale, and advance this research.

Applicable Materials

The successful replication and optimization of this BiVO$_{4}$/BDD photoanode require highly uniform, conductive p-type diamond.

Material Recommendation: Heavy Boron-Doped PCD (Polycrystalline Diamond).
- Justification: The paper requires a p-type BDD film with a high carrier density (10$^{18}$ cm^-3) to act as the hole-rich ultra-micro electrode. 6CCVD specializes in producing highly conductive BDD via advanced MPCVD, offering superior purity, uniformity, and robustness compared to the HFCVD method used in the study.
Substrate Options: 6CCVD can supply BDD films grown on various substrates, including conductive Si (as used in the paper) or large-area intrinsic PCD for maximum thermal and chemical stability.

Customization Potential

The optimization process relied heavily on precise control over the BDD film properties and subsequent interface engineering. 6CCVD’s capabilities directly address these needs:

Research Requirement	6CCVD Customization Capability
Precise Thickness Control	We offer BDD films with thickness control from 0.1 µm up to 500 µm (PCD), allowing researchers to fine-tune the p-n junction depth and optimize charge transport efficiency, mirroring the critical T$_{d}$ optimization in the M30 sample.
Scalability & Large Area	6CCVD provides custom plates and wafers up to 125 mm (PCD). This is essential for transitioning PEC photoanodes from lab-scale Si substrates to practical, industrial-scale energy and environmental applications.
Surface Quality for Deposition	Our advanced polishing achieves surface roughness (Ra) of < 5 nm for inch-size PCD. This ultra-smooth, low-defect surface is ideal for subsequent thin-film deposition techniques like Magnetron Sputtering (MS) used for the BiVO$_{4}$ layer.
Electrode Integration	The device requires robust electrical contacts (Ag contacts were shown). 6CCVD offers in-house metalization services, including Au, Pt, Pd, Ti, W, and Cu, to ensure reliable ohmic contacts and seamless integration into electrochemical cells.
Global Logistics	We provide reliable Global Shipping (DDU default, DDP available) to ensure rapid delivery of custom diamond materials worldwide.

Engineering Support

The successful development of novel heterojunction photoanodes, particularly for complex applications like PEC water splitting and organic pollutant degradation (TCH), requires deep material expertise.

6CCVD’s in-house PhD team offers comprehensive engineering support for projects involving:

Material selection and doping optimization for specific p-n heterojunction requirements.
Interface engineering and surface termination strategies to maximize charge separation efficiency.
Custom dimensions and metalization schemes for PEC and EC device integration.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Constructing heterojunction is an attractive strategy for promoting photoelectrochemical (PEC) performance in water splitting and organic pollutant degradation. Herein, a novel porous BiVO4/Boron-doped Diamond (BiVO4/BDD) heterojunction photoanode containing masses of ultra-micro electrodes was successfully fabricated with an n-type BiVO4 film coated on a p-type BDD substrate by magnetron sputtering (MS). The surface structures of BiVO4 could be adjusted by changing the duration of deposition (Td). The morphologies, phase structures, electronic structures, and chemical compositions of the photoanodes were systematically characterized and analyzed. The best PEC activity with the highest current density of 1.8 mA/cm2 at 1.23 VRHE was achieved when Td was 30 min, and the sample showed the highest degradation efficiency towards tetracycline hydrochloride degradation (TCH) as well. The enhanced PEC performance was ascribed to the excellent charge transport efficiency as well as a lower carrier recombination rate, which benefited from the formation of BiVO4/BDD ultra-micro p-n heterojunction photoelectrodes and the porous structures of BiVO4. These novel photoanodes were expected to be employed in the practical PEC applications of energy regeneration and environmental management in the future.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules27165218

References

2022 - Heterojunction photoanode of SnO2 and Mo-Doped BiVO4 for boosting photoelectrochemical performance and tetracycline hydrochloride degradation [Crossref]
2021 - Stable unbiased photo-electrochemical overall water splitting exceeding 3% efficiency via covalent triazine framework/metal oxide hybrid photoelectrodes [Crossref]
2014 - Semiconductor heterojunction photocatalysts: Design, construction, and photocatalytic performances [Crossref]
2020 - Tunable photo-electrochemistry of patterned TiO2/BDD heterojunctions [Crossref]
2016 - Charge separation in TiO2/BDD heterojunction thin film for enhanced photoelectrochemical performance [Crossref]
2019 - Use of boron-doped diamond electrodes in electro-organic synthesis [Crossref]
2019 - Conductive diamond: Synthesis, properties, and electrochemical applications [Crossref]
2021 - Photoelectrocatalytic degradation of glyphosate on titanium dioxide synthesized by sol-gel/spin-coating on boron doped diamond (TiO2/BDD) as a photoanode [Crossref]
2022 - Enhanced visible-light-driven photoelectrochemical activity in nitrogen-doped TiO2/boron-doped diamond heterojunction electrodes [Crossref]