The design of an efficient and selective catalyst for hydrogen peroxide (H2O2) formation is highly sought due to its industrial importance. As alternatives to a conventional Pd-Au alloy-based catalyst, three cuboctahedral core-shell nanoclusters (Au19@Pt60, Co19@Pt60 and Au10Co9@Pt60 NCs) have been investigated. Their catalytic activities toward H2O2 formation have been compared with that of pure Pt cuboctahedral NC (Pt79). Much attention has been devoted to thermodynamic and kinetic parameters to find out the feasibility of the two-electron (2e-) over the four-electron (4e-) oxygen reduction reaction (ORR) to improve the product selectivity (H2O vs. H2O2). Elementary steps corresponding to H2O2 formation are significantly improved over the Au10Co9@Pt60 NC catalyst compared with the pure core-shell NCs and periodic surface based catalysts. Furthermore, the Au10Co9@Pt60 NC favours H2O2 formation via the much desired Langmuir-Hinshelwood mechanism. The potential-dependent study shows that the H2O2 formation is thermodynamically favourable up to 0.43 V on the Au10Co9@Pt60 NC and thus the overpotential for the 2e- ORR process is significantly lowered. Besides, the Au10Co9@Pt60 NC is highly selective for H2O2 formation over H2O formation. © 2017 The Royal Society of Chemistry.