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Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

preprint
submitted on 31.03.2021, 13:43 and posted on 01.04.2021, 06:17 by Julia Kröger, Alberto Jiménez-Solano, Gökcen Savasci, Vincent Wing-hei Lau, Viola Duppel, Igor Moudrakovski, Kathrin Küster, Tanja Scholz, Andreas Gouder, Marie Luise Schreiter, Filip Podjaski, Christian Ochsenfeld, Bettina Lotsch
The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.

Funding

Fuel from sunlight: Covalent organic frameworks as integrated platforms for photocatalytic water splitting and CO2 reduction

European Research Council

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DFG cluster of excellence “e-conversion” (EXC 2089/1-390776260)

Max Planck Society

History

Email Address of Submitting Author

F.Podjaski@fkf.mpg.de

Institution

Max-Planck-Institute for Solid State Research

Country

Germany

ORCID For Submitting Author

0000-0002-5428-4526

Declaration of Conflict of Interest

The authors declare no conflict of interest.

Version Notes

submitted manuscript

Exports