Photocatalytic H₂ production and degradation of aqueous 2-chlorophenol over B/N-graphene-coated Cu⁰/TiO₂

A DFT, experimental and mechanistic investigation

verfasst von

Lucy M. Ombaka, James D. McGettrick, Ekemena O. Oseghe, Osama Al-Madanat, Felix Rieck genannt Best, Titus A.M. Msagati, Matthew L. Davies, Thomas Bredow, Detlef W. Bahnemann

Abstract

Energy and environmental challenges are global concerns that scientists are interested in alleviating. It is on this premise that we prepared boron/nitrogen graphene-coated Cu⁰/TiO₂ (B/N-graphene-coated Cu/TiO₂) photocatalyst of varying B:N ratios with dual functionality of H₂ production and 2-Chlorophenol (2-CP) degradation. In-situ coating of Cu⁰ with B/N-graphene is achieved via solvothermal synthesis and calcination under an inert atmosphere. All B/N-graphene-coated Cu/TiO₂ exhibit higher photonic efficiencies (5.68%–7.06% at 300 < λ < 400 nm) towards H₂ production than bare TiO₂ (0.25% at 300 < λ < 400 nm). Varying the B:N ratio in graphene influences the efficiency of H₂ generation. A B:N ratio of 0.08 yields the most active composite exhibiting a photonic efficiency of 7.06% towards H₂ evolution and a degradation rate of 4.07 × 10⁻² min⁻¹ towards 2-chlorophenol (2-CP). Density functional theory (DFT) investigations determine that B-doping (p-type) enhances graphene stability on Cu⁰ while N-doping (n-type) increases the reduction potential of Cu⁰ relative to H⁺ reduction potential. X-ray photoelectron spectroscopy reveals that increasing the B:N ratio increases p-type BC₂O while decreasing n-type pyridinic-N in graphene thus altering the interlayer electron density. Isotopic labelling experiments determine water reduction as the main mechanism by which H₂ is produced over B/N-graphene-coated Cu/TiO₂. The reactive species involved in the degradation of 2-CP are holes (h⁺), hydroxyl radical (OH^•), and O₂^•-, of which superoxide (O₂^•-) plays the major role. This work displays B/N -graphene-coated Cu/TiO₂ as a potential photocatalyst for large-scale H₂ production and 2-CP degradation.

Organisationseinheit(en)

Institut für Technische Chemie
Institut für Physikalische Chemie und Elektrochemie
Laboratorium für Nano- und Quantenengineering

Externe Organisation(en)

Technical University of Kenya (TU-K)
Swansea University
University of South Africa
University of KwaZulu-Natal
Rheinische Friedrich-Wilhelms-Universität Bonn
Staatliche Universität Sankt Petersburg

Typ

Artikel

Journal

Journal of Environmental Management

Band

311

ISSN

0301-4797

Publikationsdatum

06.2022

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Environmental engineering, Abfallwirtschaft und -entsorgung, Management, Monitoring, Politik und Recht

Ziele für nachhaltige Entwicklung

SDG 7 – Erschwingliche und saubere Energie

Elektronische Version(en)

https://doi.org/10.1016/j.jenvman.2022.114822 (Zugang: Geschlossen)