Solid-state dewetting

In this sub-project we demonstrated the use of solid state dewetting[1,2] of thin metal films to co-catalyze TiO2 nanocavity arrays with metal co-catalyst nanoparticles for photocatalytic H2 evolution.[3]
We focused on dewetting of noble metals such as Au[4] and Pt.[5] We achieved full control on key experimental parameters to tune noble metal particle size, distribution and loading on the oxide photo-active surface. We also explored dewetting of metal bilayers to enable dewetting-alloying effects. The latter were used to form alloy nanoparticles, e.g. AuAg or PtNi, from which less noble elements (Ag, Ni) were selectively removed by dealloying, thus forming porous Au or Pt co-catalytic nanoparticles.[6,7] Dewetting-alloying principle were also exploited to functionalize oxide nanocavities with dewetted NiCu nanoparticles that showed remarkable noble metal free photocatalytic H2 evolution performances.[8,9]


Particle-in-cavity arrays and advanced photocatalysis

We identified key anodizing and dewetting parameters to tune the dimensions of oxide cavities and catalyst particles, respectively. We accomplished high active metal (e.g. Pt, Au) particle surfaces and maximized carrier transfer from-oxide-to-particle and from-particle-to-environment, resulting in enhanced photocatalytic reaction rates with minimized noble metal catalyst loadings.[4,10,11] We also demonstrated the integration of dewetted plasmonic metal (e.g. Au) nanoparticles into photo-electrodes for solar water splitting.[12]
Particle reactivity and economy were improved further by (i) dewetting-alloying[8] or (ii) dealloying effects.[6,7] (i) enabled electronic effects, such as in AuPt[13] catalytic nanoparticles, that were proved to support faster H2 evolution kinetics. (ii) led to porous (e.g. spongy Au, Pt, AuPt or AuPtAg[6,7,14]) nanoparticles, with reduced noble metal content, providing enhanced photocatalytic performances due to their high surface area and density of surface reaction sites.
Alloying principles were used also to develop non-noble metal catalyst particles, e.g. NiCu nanoparticles, which resulted significantly more active than individual Ni or Cu counterparts, and reached performances comparable to Pt catalyst benchmarks.[8,9] Furthermore, we also achieved high activity along with remarkable tolerance against poisoning (from alcohol oxidation products) with dewetted Pt based alloy nanocatalysts, e.g. PtCu systems.[15]

Some literature citations:
[1] C. V. Thompson, Annu. Rev. Mater. Res. 2012, 42, 399.
[2] F. Leroy, Ł. Borowik, F. Cheynis, Y. Almadori, S. Curiotto, M. Trautmann, J. C. Barbe, P. Muller, Surf. Sci. Rep. 2016, 71, 391.
[3] M. Altomare, N. T. Nguyen, P. Schmuki, Chem. Sci. 2016, 7, 6865.
[4] J. E. Yoo, K. Lee, M. Altomare, E. Selli, P. Schmuki, Angew. Chemie Int. Ed. 2013, 52, 7514.
[5] J. Yoo, M. Altomare, M. Mokhtar, A. Alshehri, S. A. Al-Thabaiti, A. Mazare, P. Schmuki, J. Phys. Chem. C 2016, 120, 15884.
[6] N. T. Nguyen, M. Altomare, J. Yoo, P. Schmuki, Adv. Mater. 2015, 27, 3208.
[7] L. Ji, D. Spanu, N. Denisov, S. Recchia, P. Schmuki, M. Altomare, Chem. - An Asian J. 2019, asia. 201901545.
[8] D. Spanu, S. Recchia, S. Mohajernia, O. Tomanec, S. Kment, R. Zboril, P. Schmuki, M. Altomare, ACS Catal. 2018, 8, 5298.
[9] D. Spanu, A. Minguzzi, S. Recchia, F. Shahvardanfard, O. Tomanec, R. Zboril, P. Schmuki, P. Ghigna, M. Altomare, ACS Catal. 2020, 10, 8293.
[10] N. T. Nguyen, J. Yoo, M. Altomare, P. Schmuki, Chem. Commun. 2014, 50.
[11] N. T. Nguyen, M. Altomare, J. E. Yoo, N. Taccardi, P. Schmuki, Adv. Energy Mater. 2016, 6, 1501926.
[12] M. Licklederer, R. Mohammadi, N. T. Nguyen, H. Park, S. Hejazi, M. Halik, N. Vogel, M. Altomare, P. Schmuki, J. Phys. Chem. C 2019, 123, 16934.
[13] H. Bian, N. T. Nguyen, J. Yoo, S. Hejazi, S. Mohajernia, J. Muller, E. Spiecker, H. Tsuchiya, O. Tomanec, B. E. Sanabria-Arenas, R. Zboril, Y. Y. Li, P. Schmuki, ACS Appl. Mater. Interfaces 2018, 10, 18220.
[14] N. T. Nguyen, S. Ozkan, O. Tomanec, X. Zhou, R. Zboril, P. Schmuki, J. Mater. Chem. A 2018, 6, 13599.
[15] F. Shahvaranfard, P. Ghigna, A. Minguzzi, E. Wierzbicka, P. Schmuki, M. Altomare, Under Consid.