Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivityElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ta06817d

• Main Authors: Pramana, Stevin S, Cavallaro, Andrea, Li, Cheng, Handoko, Albertus D, Chan, Kuang Wen, Walker, Robert J, Regoutz, Anna, Herrin, Jason S, Yeo, Boon Siang, Payne, David J, Kilner, John A, Ryan, Mary P, Skinner, Stephen J
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta06817d

A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO 2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm −1 ) was found for the double perovskite of composition GdBa 0.6 Sr 0.4 Co 2 O 6− δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa 1− x Sr x Co 2 O 6− δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P 4/ mmm space group in comparison with the undoped GdBaCo 2 O 6−δ which is orthorhombic ( Pmmm ), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co-O-Co buckling angles and Co-O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface. Upon Sr-doping in GdBa 1− x Sr x Co 2 O 6− δ , a shift of the valence band maximum VB max towards the Fermi energy E F was observed leading to better OER activity.