Photocatalytic Overall Water Splitting: Observing H 2 and O 2 Transients with Ni/NiO x -Modified Mg:SrTiO 3

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2019-01; no. 31; p. 1666
• Main Authors: Mei, Bastian Timo, Han, Kai, Mul, Guido
• Format: Journal Article
• Language: English
• Published: 01.05.2019
• ISSN: 2151-2043; 2151-2035
• DOI: 10.1149/MA2019-01/31/1666

SrTiO 3 is a promising semiconductor driving photocatalytic overall water splitting (POWS) under UV light illumination. Improving the performance of SrTiO 3 in decomposing water into H 2 and O 2 can be achieved by introducing feasible co-catalyst, such as Pt or Ni/NiO x . Though co-catalysts are employed in heterogeneous photocatalysis engineering of semiconductor/co-catalysts interfaces is rarely reported in literature [1]. In addition, limited attention has been paid to structural/electronic changes of co-catalysts during illumination/reaction and transients occurring in hydrogen and/or oxygen evolution are barely discussed. In this contribution the photocatalytic performance of SrTiO 3 -based systems will be analyzed using a Continuously Stirred Tank Reactor (CSTR) connected to a micro GC-PDD (Pulsed Discharge Detector). Due to the favorable time-resolution of the GC-PDD transients in the evolution of H 2 and O 2 , especially in the initial stages of testing, can be easily revealed. We will highlight the following recent observations: For Ni/NiO x -modified SrTiO 3 , severe changes in the oxidation state of NiO x assigned to the transformation of Ni(OH) 2 to NiOOH leading to an active photocatalyst/co-catalyst material in agreement with transient H 2 evolution will be discussed [2]; Electronic modification of SrTiO 3 by Mg incorporation into the perovskite structure can be obtained by a simple solid-state preparation [3]. While significant improvements in the steady state photocatalytic efficiency are obtained (Fig. 1), we also observed drastic changes in the initial transients caused by the interaction of Mg and Ni/NiO x ; Finally, it will be highlighted that stabilization of the Ni/NiO x -modified Mg:SrTiO 3 photocatalyst is obtained by photodeposition of CrO x from Cr(VI) containing solutions [4]. Enhanced stability is probably caused by electronic modification of Ni/NiO x as a severe influence of the back reaction of H 2 and O 2 was not observed for the process conditions used. Finally, the general stability of SrTiO 3 in aqueous environment will be discussed. Thus, using state-of-the-art micro-GC analysis we were able to design a stable composite photocatalyst and improve the efficiency of the system (AQE) from 0.6% to >40%. References [1] B. Mei, K. Han, G. Mul, ACS Catal ., 2018 , 8, 9154-9164; [2] K. Han, T. Kreuger, B. Mei, G. Mul, ACS Catal ., 2017 , 7, 1610-1614; [3] K. Han, Y. Lin, C. Yang, R. Jong, G. Mul, B. Mei, ChemSusChem , 2017 , 10, 4510 – 4516. [4] K. Han, B. Mei, et al., to be submitted