Silicon nanowires' based photoanode for hydrogen evolution P. Dytrych a,b , V. Drinek a , J. Bumba a , F. Kastanek a , O. Solcova a,* a Institute of Chemical Process Fundamentals of the CAS, v.v.i. Rozvojova 135/1, Prague 6, 16502, Czech Republic b Institute of Electrochemistry, University of Ulm, Albert-Einstein-Alle 47, 89081 Ulm, Germany article info Article history: Received 11 December 2017 Received in revised form 26 March 2018 Accepted 11 April 2018 Available online xxx Keywords: Hydrogen storage Hydrogen evolution reaction Metal nanoparticles (photo)electrochemistry (photo)eletrolysis of water abstract The solar driven photo-electrolysis of water for hydrogen and nanoparticles formation from electrolyte with corresponding metal salts was investigated. The photoanode con- sisted of a thin layer of silicon nanowires deposited on molybdenum and a platinum wire as the cathode was used. The prepared photo-anodes were stable up to 0.3 V against the saturated Ag/AgCl electrode without any signs of gaseous oxygen evolution. This photo- electrochemical system enhanced the nanoparticle formation during the illumination phase accompanied with lowering the external potential needed. The present results show that hydrogen in statu nascendi is formed during illumination of photoanode, which causes the formation of nanoparticles by reduction of metal salts. During the photo drive elec- trolysis, hydrogen is stored in/on forming nanoparticles. The size of nanoparticles can be determined by time and an external bias value inserted between the working and platinum electrodes in a classical three electrode system. It was confirmed that the formation of nanoparticles was limited by diffusional processes of hydrogen in statu nascendi in elec- trolyte, which is in agreement with literature. © 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Energy and environmental issues at a global level belong to the most important topics. It is indispensable to construct clean energy systems in order to solve the issues. Hydrogen will play an important role in such systems due to the fact that it is the ultimate clean energy and it can be used in fuel cells. The use of solar energy for electricity generation and the use of this electricity for hydrogen production by alkaline water electrolysis promises to be a truly sustainable scheme for hydrogen economy [1e3]. There are several ways of solar hydrogen production and storage [4e7]. One of them is the photocatalytic water splitting process, in which the photon energy is converted into chem- ical energy accompanied with a largely positive change in the Gibbs free energy through water splitting [8e10]. This reaction is similar to photosynthesis used by green plants because these are uphill reactions. Therefore, photocatalytic water splitting is regarded as an artificial photosynthesis and is an attractive and challenging theme in chemistry. During the past 40 years, various photocatalyst materials have been developed to split water into H 2 and O 2 under UV and visible light illumination. However, efficient materials for water splitting under visible light irradiation have not been found yet. Nevertheless, new photocatalyst materials for water splitting have recently been discovered one after another. One of the perspective material is the * Corresponding author. E-mail address: solcova@icpf.cas.cz (O. Solcova). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2018) 1 e6 https://doi.org/10.1016/j.ijhydene.2018.04.244 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Dytrych P, et al., Silicon nanowires' based photoanode for hydrogen evolution, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.04.244