ENERGY MATERIALS Ni supported on YSZ: XAS and XPS characterization and catalytic activity for CO 2 methanation Jagadesh Kopula Kesavan 1 , Igor Luisetto 1, * , Simonetta Tuti 1 , Carlo Meneghini 1 , Chiara Battocchio 1 , and Giovanna Iucci 1 1 Department of Science, ‘Roma Tre’ University, Via della Vasca Navale 79, 00146 Rome, Italy Received: 4 April 2017 Accepted: 5 May 2017 Ó Springer Science+Business Media New York 2017 ABSTRACT Ni supported on yttrium-stabilized zirconium oxide catalysts have been pre- pared by electroless plating method. Structure, electronic and chemical state of Ni as a function of Ni content (1, 7 and 12 wt%) have been characterized combining X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelec- tron spectroscopy, temperature-programmed reduction (H 2 -TPR) and BET. The catalytic activity for the CO 2 methanation was studied in the 250–500 °C tem- perature range, finding the highest CO 2 conversion and CH 4 selectivity for the catalyst with the largest Ni loading. A dependence of activity and CH 4 selec- tivity on Ni crystallites size was highlighted. Introduction Renewable sources of energy are naturally intermit- tent depending on season, weather, day–night con- dition and so on [1, 2]. Therefore, the increasing use of renewable energies is accompanied by the need of efficient technologies to store the produced energy. The transformation of ‘‘green’’ electrical energy in hydrogen through the water electrolysis, the so-called power to gas technology (PtG), seems to be the most advantageous method [3]. However, hydrogen is difficult to store and transport and only fuel cells can be efficiently used for its conversion into electrical energy when demanded. The transformation of hydrogen into CH 4 by the methanation reaction CO 2 þ 4H 2 ! CH 4 þ 2H 2 O ð Þ has been recognized as a valuable way to overcome the issue of hydrogen as energy vector, because methane can be easily stored in gas reservoirs, transported via the existing gas grid and reconverted to electrical energy using a large variety of existing and well-developed technologies [4, 5]. Furthermore, it may be directly used as fuel for transport and energy resource for industrial and civil applications. The methanation reaction can exploit CO 2 obtained from different sources such as fossil power plants, cement industry, fermentations or even from atmo- sphere, and it is recognized as the most promising way to valorize CO 2 [1, 6]. The CO 2 methanation is exothermic and thermodynamically favored (DH 298K =-164.0 kJ/mol; DG 298K =-130.8 kJ/mol); however, it is an eight-electron process with com- pelling kinetic limits and it occurs above 250 °C in the presence of catalysts. Ni-based catalysts have been extensively studied for CO 2 methanation for indus- trial purpose, thanks to their low cost and high Address correspondence to E-mail: igor.luisetto@uniroma3.it DOI 10.1007/s10853-017-1179-2 J Mater Sci Energy materials