As most chemical reactions happen on surfaces, nanoparticles are ideal for heterogeneous catalysis due to their optimal surface to volume ratio. Alloying two metals can furthermore improve catalytic performance by increasing selectivity, activity or resistance to poisoning due to electronic or geometric effects. Tuning nanoalloy morphology may even enhance catalytic properties by controlling reactivity and/or selectivity. The properties of nanoparticles are also under the influence of a substrate in real world applications. Hence, an accurate description of nanocluster-support interaction is important in nanoalloy catalysis applications and can be achieved by atomistic modelling based on first principle electronic structure calculations. We will present recent studies of fcc-Au-Rh [1-4] and Pd-Ir [5,6] nanoalloys supported on TiO2(110). In experimental studies, TiO2 has been used as a substrate because it has well defined single phase nanorods (which are suitable for structural analysis) and it is a reducible oxide (which can act as an oxygen reservoir and enhance the catalytic activity) [1]. We have studied the relative stabilities of different chemical ordering arrangements of the Au-Rh and Pd-Ir nanoalloys, for a range of compositions [2,5], and how these are influenced by the TiO2 substrate [4,6]. The effect of chemical ordering and the substrate on the strength of adsorption of small adsorbates such as H2, O2 and CO will be discussed [3,4]. 1. Z. Konuspayeva, P. Afanasiev, T.S. Nguyen, L. Di Felice, F. Morfin, N.T. Nguyen, J. Nelayah, C. Ricolleau, Z.Y. Li, J. Yuan, G. Berhault and L. Piccolo, Phys. Chem. Chem. Phys. 17, 28112–28120 (2015).. 2.L. Piccolo, Z. Y. Li, I. Demiroglu, F. Moyon, Z. Konuspayeva, G. Berhault, P. Afanasiev, W. Lefebvre, J. Yuan and R. L. Johnston, Sci. Rep. 6, 35226 (2016). 3.I. Demiroglu, Z. Y. Li, L. Piccolo and R. L. Johnston, Cat. Sci. Technol. 6, 6916–6931 (2016). 4.I. Demiroglu, Z. Y. Li, L. Piccolo and R. L. Johnston, Comput. Theor. Chem. 1107, 142–151 (2017). 5.T.-E Fan, I. Demiroglu, H. A. Hussein, T.-D. Liu and R. L. Johnston, Phys. Chem. Chem. Phys. 19, 27090–27098 (2017). 6.I. Demiroglu, T.-E Fan, Z. Y. Li, J. Yuan, T.-D. Liu, L. Piccolo and R. L. Johnston, Faraday Discussions DOI: 10.1039/C7FD00213K (2018).