Reaction Mechanism of Hydrogen Generation and Nitrogen Fixation at Carbon Nitride/Double Perovskite Heterojunctions
Costanza Tedesco a, Luca Gregori b, Angelica Simbula c, Federico Pitzalis c, Andrea Speltini a, Francesca Merlo a, Silvia Colella d, Andrea Listorti e, Edoardo Mosconi f g, Asma A. Alothman g, Waldemar Kaiser h, MIchele Saba b, Antonella Profumo a, Filippo De Angelis b f g h, Lorenzo Malavasi a
a Department of Chemistry and INSTM, University of Pavia,Via Taramelli 16, Pavia, 27100, Italy
b Department of Chemistry, Biology and Biotechnology, University of Perugia and INSTM, Via Elce di Sotto 8, 06123 Perugia, Italy
c Dipartimento di Fisica, Università di Cagliari, 09042 Monserrato, Italy
d CNR NANOTEC - c/o Dipartimento di Chimica, Università di Bari, Via Orabona 4, 70126 Bari, Italy
e Department of Chemistry, University of Bari “Aldo Moro”, via Orabona 4, 70126, Bari, Italy
f Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Chimiche “Giulio Natta” (CNR-SCITEC), Via Elce di Sotto 8, 06123 Perugia, Italy
g Chemistry Department, College of Science, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia
h SKKU Institute of Energy Science and Technology (SIEST) Sungkyunkwan University, Suwon, Korea 440-746
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2024 Conference (MATSUS24)
#PEROCAT - Metal Halide Perovskite Photocatalysis
Barcelona, Spain, 2024 March 4th - 8th
Organizers: Andrea Listorti and Lorenzo Malavasi
Oral, Costanza Tedesco, presentation 194
DOI: https://doi.org/10.29363/nanoge.matsus.2024.194
Publication date: 18th December 2023

Photocatalytically active heterojunctions based on metal halide perovskites (MHPs) are drawing significant interest for their chameleon ability to foster several redox reactions. The lack of mechanistic insights into their performance, however, limits the ability of engineering novel and optimized materials. Herein, we report on a composite system including a double perovskite, Cs2AgBiCl6/g-C3N4, used in parallel for solar-driven hydrogen generation and nitrogen reduction. The composite efficiently promotes the two reactions, but its activity strongly depends on the perovskite/carbon nitride relative amounts. Through advanced spectroscopic investigation and density function theory modelling we studied the H2 and NH3 production reaction mechanisms, finding perovskite halide vacancies as the primary reactive sites for hydrogen generation, withstanding a positive contribution of low loaded g-C3N4, in reducing carrier recombination. For nitrogen reduction, instead, the active sites are g-C3N4 nitrogen vacancies, and the heterojunction best performs at low perovskites loadings, as the composites maximizes light absorption and reduced carrier losses. We believe these insights are important add-ons towards universal exploitation of MHPs in contemporary photocatalysis.

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