Photocatalysis constitutes a rapidly developing research field that provides access to a number of unique redox chemistries by means of light-assisted catalysis. Photocatalytic processes include waste water treatment and air purification, selective oxidation and reduction reactions, as well as CO₂ valorization and water splitting. Contemporary heterogeneous photocatalysts, however, still suffer from three main shortcomings: insufficient absorption in the visible light range, extensive electron-hole recombination and rather poor catalytic properties of bare photocatalyst surface. Focused fundamental investigations are required to further develop and commercialize the field.
One essential step in addressing these challenges is not only synthesis and characterization of new photocatalysts, but also evaluation of their photocatalytic performance to unravel structure-property relations. Currently our group uses several tools to directly measure or evaluate photocatalytic activity of a wide range of materials.
Our methods include photocatalytic water treatment (decomposition of organics) and photocatalytic water splitting (hydrogen and/or oxygen evolution) experiments that we perform using home-build liquid phase and gas phase reactors. Here we employ a variety of tunable light sources (UV- and visible light-based as well as solar simulators) and optical cut-off filters to reveal the interplay between the photocatalyst structure, its light absorption properties and photocatalytic performance. Aside from conventional gas chromatography, that we use to detect and quantify reaction products, our water splitting reactors are equipped with an on-line gas detection system able to in situ quantify hydrogen and oxygen (products of interest) as well as major side products (e.g. CO and CO₂ ). This unique system, for example, allows us to follow initial steps of the photocatalytic reactions and get crucial mechanistic insights.
By using our experimental setups we could identify the role of the interface and morphology in CNT-Ta₂O₅ hybrids, investigate impact of preparation and post-treatment of TiO₂-based electrospun fibres, reveal the role of non-covalent functionalization on the quality of the ALD-based ZnO hybrids, follow Pt encapsulation by TiO₂ during photocatalysis, as well as design ordered mesoporous Ta2O5 with highly-accessible surface area:
S. Cherevan, P. Gebhardt, C. J. Shearer, M. Matsukawa, K. Domen, D. Eder, Energy Environ. Sci. 2014, 7, 791–796; DOI:10.1039/C3EE42558D.
A. Moya, A. Cherevan, S. Marchesan, P. Gebhardt, M. Prato, D. Eder, J. J. Vilatela, Applied Catalysis B: Environmental 2015, 179, 574–582; DOI:10.1016/j.apcatb.2015.05.052.
N. Kemnade, C. J. Shearer, D. J. Dieterle, A. S. Cherevan, P. Gebhardt, G. Wilde, D. Eder, Nanoscale 2015, 7, 3028–3034; DOI:10.1039/C4NR04615C.
Hybrid Perovskite Solar Cells
We are working on high efficiency, low-cost, hole-conductor-free perovskite solar cells with TiO₂ as the electron transport layer (ETL) and carbon as the hole collection layer, that functions in ambient air.
To achieve high efficiency, atomic layer deposition (ALD) was introduced to prepared uniform, pinhole-free TiO₂ blocking layer of various thicknesses on fluorine-doped tin oxide (FTO) electrodes. Based on these TiO₂ blocking layers, a series of hole conductor-free perovskite solar cells (PSCs) were fabricated in ambient air. The optimal compact layer thickness was investigated with power conversion efficiency and electrochemical impedance measurement. This part of work is being done in collaboration with Li Wan’s Group, Hubei University. In the future, we will also explore the ALD possibility of different type of blocking materials.
To improve the electron collection efficiency and open current voltage, we are currently working at the interface optimization in the PSC by adding an organic monolayer between the ETL and perovskite.
H. Hu, B. Dong, H. Hu, F. Chen, M. Kong, Q. Zhang, T. Luo, L. Zhao, Z. Guo, J. Li, Z. Xu, S. Wang, D. Eder, L. Wang, ACS Appl. Mater. Interfaces 2016, 8, 17999–18007; DOI:10.1021/acsami.6b02701.