Reactor Design for Nanoparticle-Based 3-Dimensional Photocatalysts

Multiscale nanoparticle assembly is at the heart of efforts to integrate nanoparticles into macroscopic materials and devices [1]. The idea of arranging nanoparticles in a modular and defined way to larger entities is extremely appealing, because in such a way a nearly indefinite number of different architectures is accessible from a limited set of building blocks. Among the many geometries, 3-dimensional structures like aerogels are unique in the sense that the size-specific properties of the nanobuilding blocks are fully preserved in the macroscopic material [2]. With their extensive porosity and large surface areas aerogels are particularly attractive for applications in gas-phase photocatalysis [3]. Moreover, if they can be produced in monolithic form with sizes in the centimeter range, completely new possibilities and challenges open up, which are also associated with interesting scientific and technical questions. In particular, gas flow through and the penetration of light into the macroscopic bodies represent important parameters that must be taken into account in the development of suitable photoreactors [4-7]. Only if the macroscopic shape of the aerogel and the reactor design are perfectly matched can the full photocatalytic performance of the aerogel be exploited [7]. Based on photocatalytic methanol reforming as a model reaction, this presentation will show how all these aspects are interrelated and how they have to be optimized to increase the hydrogen production rate.<br/><br/>[1] M. Niederberger, Multiscale Nanoparticle Assembly: From Particulate Precise Manufacturing to Colloidal Processing, Adv. Funct. Mater. 2017, 27, 1703647<br/>[2] F. Rechberger, M. Niederberger, Synthesis of Aerogels: From Molecular Routes to 3-Dimensional Nanoparticle Assembly, Nanoscale Horiz. 2017, 2, 6<br/>[3] M. Schreck, M. Niederberger, Photocatalytic Gas Phase Reactions, Chem. Mater. 2019, 31, 597<br/>[4] A. L. Luna, F. Matter, M. Schreck, J. Wohlwend, E. Tervoort, C. Colbeau-Justin, M. Niederberger, Monolithic Metal-Containing TiO2 Aerogels Assembled from Crystalline Pre-formed Nanoparticles as Efficient Photocatalysts for H2 Generation, Appl. Catal., A 2020, 267, 118660<br/>[5] A. L. Luna, S. Papadopoulos, T. Kyburz, E. Tervoort, L. Novotny, M. Niederberger, Insights into light and mass transport in nanoparticle-based aerogels: the advantage of monolithic 3D photocatalysts, J. Mater. Chem. A 2021, 9, 22380<br/>[6] M. Schreck, N. Kleger, F. Matter, J. Kwon, E. Tervoort, K. Masania, A. R. Studart, M. Niederberger, 3D Printed Scaffolds for Monolithic Aerogel Photocatalysts with Complex Geometries, Small 2021, 17, 2104089<br/>[7] J. Kwon, K. Choi, E. Tervoort, M. Niederberger, One-pot microwave synthesis of Pd modified titanium dioxide nanocrystals for 3D aerogel monoliths with efficient visible-light photocatalytic activity in a heated gas flow reactor, J. Mater. Chem. A 2022, 10, 18383<br/>[8] F. Matter, M. Niederberger, The Importance of the Macroscopic Geometry in Gas-Phase Photocatalysis, Adv. Sci. 2022, 9, 2105363