1 ADDITIVE EFFECTS OF STEAM ADDITION AND HBr DOPING FOR CaO-BASED SORBENTS FOR CO2 CAPTURE Belén González ,a, b† , John Blamey a , Mohamad J. Al-Jeboori a , Nicholas H. Florin c , Peter Clough a , Paul S. Fennell a * a Department of Chemical Engineering and Chemical Technology, Imperial College London, London, SW7 2AZ, United Kingdom. b Instituto Nacional del Carbón, (CSIC), Francisco Pintado Fé 26, 33011, Oviedo, Spain. c Calix Limited, Level 1, 9 Bridge Street, Pymble, NSW 2073, Australia. * Corresponding author: Tel: +44 (0) 20 7594 6637. Fax: +44 (0) 20 7594 5638. E-mail: p.fennell@imperial.ac.uk † Present address: Department of Chemical Engineering and Biotechnology. University of Cambridge, CB2 3RA, United Kingdom.