Discovering photocathode materials and hydrogen evolution catalysts by high-throughput experimentation

HElge Stein, Ruhr-Universität Bochum, Bochum, Germany
Ramona Gutkowski, Ruhr-Univerisität Bochum, Bochum, Germany
Kirill Sliozberg, Ruhr-Univerisität Bochum, Bochum, Germany
Chinmay Khare, Ruhr-Univerisität Bochum, Bochum, Germany
Wolfgang Schuhmann, Ruhr-Univerisität Bochum, Bochum, Germany
Alfred Ludwig, Ruhr-Univerisität Bochum, Bochum, Germany

Efficient photoelectrochemical water splitting materials are needed for a future hydrogen economy. In this contribution, we will present results from a combinatorial materials science workflow that aims at identifying new photocathode materials for solar water splitting. The talk will present recent findings from the materials systems Cu-Si-Ti-O [1] and Al-Cr-Fe-O [2]. In the Al-Cr-Fe-O system Al:Cr2FeO4 was identified [2] as a new 1.5 eV bandgap absorber material with an outstanding photovoltage of 1 V and promising photocurrents. Recent results on the origin of this high photovoltage and routes to increase the photocurrent and to reduce photo generated charge carrier recombination will be addressed. Many p-type metal oxides suffer from photo corrosion during HER.

We choose Cu2O as a model material for stabilization studies [3], e.g. by alloying with third elements. From our study of the system Cu-Si-Ti-O [1], two new p-type materials based on Si:Cu3TiOx and Ti:CuSiO3 (Dioptase) were found to show promising photoelectrochemical properties and significantly better electrochemical stability compared to Cu2O. Without a co-catalyst, photocurrents of up to 430 µA/cm2 at 416 mV vs. RHE were observed under simulated AM1.5G irradiation in Si:Cu3TiOx. Finally, results from investigations of non-noble metal catalysts from the systems Co-Ni-Cu and Co-Ni-Fe for the hydrogen evolution reaction will be discussed.

[1] H. S. Stein, R. Gutkowski, A. Siegel, W. Schuhmann and A. Ludwig (2015), Ti-doped CuSiO3 as a promising material for the light induced hydrogen evolution reaction, Journal of Materials Chemistry A, 4, 3148-3152
[2] K. Sliozberg, H.S. Stein, C. Khare, B.A. Parkinson, A. Ludwig, W. Schuhmann (2015), Fe-Cr-Al containing oxide semiconductors as potential solar water splitting materials, Appl. Mater. Interfaces, 7, 4883-4889.
[3] H. S. Stein, D. Naujoks, D. Grochla, C. Khare, R. Gutkowski, S. Grützke, W.Schuhmann, A. Ludwig (2015), A structure zone diagram obtained by simultaneous deposition on a novel step heater: a case study for Cu2O thin films, Physica Status Solidi A, 212, 2798-2804

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