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A key challenge in photoelectrochemical water splitting is to fabricate nanostructured photoelectrodes with desirable properties. Herein, Ni doped BaTiO3 hollow spheres (HS) supported on reduced graphene oxide (RGO) nanocomposite were successfully synthesized by aerosol spray drying method. Former spheres consisted of small nanoparticles with size 5–20 nm possessing high porosity and large area. Characterizations were done by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). Ni doped BaTiO3 HS/RGO nanocomposites as photoanodes exhibited an enhanced photoelectrochemical performance and long-term stability compared to BaTiO3 HS and BaTiO3 HS/RGO. The photocurrent density of Ni doped BaTiO3 HS/RGO photoanode revealed 8.14 μA cm−2 which is 37% more than BaTiO3 HS. From electrochemical impedance spectroscopy (EIS) analysis, Ni doped BaTiO3 HS/RGO exhibited the lowest charge transfer resistance in comparison with BaTiO3 HS and BaTiO3 HS/RGO which leads to enhancement in the electrocatalytic activity. The successful doping of BaTiO3 HS by Ni and its loading over RGO increases the separation rate of photogenerated electrons and holes and improved the light harvesting. Ni doped BaTiO3 HS/RGO as photo-electrocatalyst exhibits excellent activity toward water oxidation capability and presents a new approach for high-efficient future photo-electrocatalysis.

There are two main industrial techniques of water electrolysis operating under near-ambient temperature and pressure conditions: alkaline water electrolysis which uses a liquid electrolyte based on an aqueous solution of potassium hydroxide [1] and PEM water electrolysis [2] which uses a solid electrolyte made of a proton-conducting polymer. Both technologies present a set of strengths and weaknesses in view of practical application in the industry sector. The objective of this communication is to highlight the differences and similarities in terms of design (cell and stack) and balance-of-plant, and to present in a critical way what are these advantages and disadvantages, from a scientific viewpoint (that of materials science, especially for the selection of electrocatalysts), from a technological viewpoint (stack design and balance-of-plant) and from an economic viewpoint (comparative analysis of capex and opex). The discussion will take into account the situation which prevails on machines at the MW-scale. Particular attention will be paid to the ability of these machines to operate under transient conditions, in particular with a view to providing services to the electricity network. Several performance indicators such as the flexibility and reactivity of machines to the demands of network operators will be used to carry out this comparison. A detailed analysis of the existing limitations will make it possible to define a set of development perspectives highlighting possible complementarities. [1] N. Guillet and P. Millet, in : Hydrogen Production: by Water Electrolysis’, chapter 4, Alkaline Water electrolysis, A. Godula-Jopek, D. Stolten Editors, Wiley-VCH (2015). [2] D. Bessarabov and P. Millet in: PEM water electrolysis, “Hydrogen and Fuel Cells Primers”, B.G. Pollet Editor, 1st Edition, Elsevier (2018).