December 1 - 6, 2024
Boston, Massachusetts

Event Supporters

2024 MRS Fall Meeting & Exhibit
EN01.02.04

Boron (B)-Doped Carbon Nitride (gC3N4) Materials for Photocatalytic Applications

When and Where

Dec 2, 2024
2:30pm - 2:45pm
Hynes, Level 3, Room 300

Presenter(s)

Co-Author(s)

Ioanna Itskou1,Andreas Kafizas1,Sharminaz Sageer2,Daniel M. Dawson2,Irena Nevjestic1,Catriona M. McGilvery1,Gwilherm Kerherve1,Sandrine Heutz1,Sharon Ashbrook2,Camille Petit1

Imperial College London1,University of St Andrews2

Abstract

Ioanna Itskou1,Andreas Kafizas1,Sharminaz Sageer2,Daniel M. Dawson2,Irena Nevjestic1,Catriona M. McGilvery1,Gwilherm Kerherve1,Sandrine Heutz1,Sharon Ashbrook2,Camille Petit1

Imperial College London1,University of St Andrews2
Graphitic carbon nitride (gC<sub>3</sub>N<sub>4</sub>) has been deployed in various applications, including photocatalysis. Among photocatalytic reactions studied, H<sub>2</sub>O splitting for the production of H<sub>2</sub> is the most common one, and carbon nitride can serve as pure catalyst, cocatalyst, catalyst support, or part of a heterojunction. Photocatalytic CO<sub>2</sub> reduction is another reaction of interest, combining utilisation of CO<sub>2</sub> emissions and production of sustainable fuels and chemicals. Research on the use of carbon nitride for this purpose is less extensive, and almost always includes the use of dopant materials or heterojunctions. For instance, the role of boron (B) as dopant for gC<sub>3</sub>N<sub>4</sub> has started to be explored but mostly for application in zinc batteries, photodegradation of organics, and photocatalytic H<sub>2</sub>O splitting/H<sub>2</sub> production. Only a couple of studies have investigated the role of B-doping on CO<sub>2</sub> photoreduction and B-gC<sub>3</sub>N<sub>4</sub> seems superior to the pristine material, for all reactions studied. Yet, the relationship between the structure/chemistry of B-doped gC<sub>3</sub>N<sub>4</sub> on its chemical, sorptive and optoelectronic properties, as well as CO<sub>2</sub> photoreducing activity remains largely unknown. If understood, a greater control of and more efficient B-doped gC<sub>3</sub>N<sub>4</sub> could be reached.<br/><br/>In our study, we aim to bridge this knowledge gap in (photo)chemistry of B-gC<sub>3</sub>N<sub>4</sub>. We produced two sets of B-doped gC<sub>3</sub>N<sub>4</sub> samples through calcination of melamine mixture with varying amount of either amorphous boron, or boric acid. Once synthesised, we characterized our samples using: XPS, solid-state NMR, XRD, (S)TEM, EELS, N<sub>2</sub> sorption (77 K), CO<sub>2</sub> sorption (288, 298, 308 K), DRS UV-Vis, steady-state PL, TAS and EPR. We confirmed the successful B-functionalisation of gC<sub>3</sub>N<sub>4</sub> using both B precursors (from 0.5 to 11 at% B), and suggest the choice of precursor affects the final chemical structure. We could control better the amount of doping using boric acid, owing to its greater reactivity with melamine. Introducing B causes oxygen (O) to be also included in the structure forming B-O bonds. Although we spot homogeneity of B-doping in bulk, heterogeneities in both morphology and elemental dispersion occur in the nm to μm scale. High B content results in increased BET area and enhanced CO<sub>2</sub> adsorption. B-doping lowers the band edges, without changing the bandgap of the material. All samples show similar tri-s-triazine structure and light absorbance, however different relaxation patterns and creation of mid-gap states. The samples share similar charge carrier lifetimes and kinetics, even though B-doping up to 5 at% increases the amount of excitons. We noticed differences in the amount of unpaired electrons, which could be linked to the chemical structure changes caused by B integration from different precursors. Most of the samples show change in EPR signal intensity before and after irradiation, an indication of excited electrons. We have also tested our materials for CO<sub>2</sub> photoreduction and photocatalytic NO<sub>x</sub> removal; in both applications, our materials exhibit different photoactivity and product selectivity than what is reported in literature. Our study provides for the first time a comparison between (i) B precursors and (ii) B-doping amounts for B-doping of C<sub>3</sub>N<sub>4</sub>, and thorough investigation of their effect on the material’s chemical, sorptive and optoelectronic properties, with differences to literature.

Keywords

nitride

Symposium Organizers

Virgil Andrei,
Rafael Jaramillo, Massachusetts Institute of Technology
Rajiv Prabhakar,
Ludmilla Steier, University of Oxford

Session Chairs

Virgil Andrei
Rafael Jaramillo

In this Session