Atomic level heterogenous catalysis has been of importance for in-depth understanding and designing of novel catalytic material. Present work aims to investigate the chemical reactivity of Au, Au 2 and Au 8 cluster on hexagonal boron nitride nano sheet (h-BN) and its Ni(111) activated analogue using density functional theory (DFT). The average vertical separation of gold atom(s) from h-BN is significantly influenced by Ni(111) support. Oxygen molecule, which is the key reactant for any oxidation reaction, is considered as probe molecule to verify the reactivity. Contrary to the case of Au atom, which is the most reactive on free-standing h-BN, Au 2 and Au 8 clusters show higher reactivity on Ni supported h-BN. Thus the agglomeration of Au (Au–Au interaction) and Ni(111) support is important in controlling the reactivity and therefore, will play a key role to design Au based efficient catalyst for future. • On free-standing h-BNNS, Au atom and Au dimer favours on top B and N atoms, respectively. • With Ni (111) supported h-BNNS both Au and Au 2 favour on-top B atom. • On free-standing h-BNNS, Au elongates the O–O bond more than Au 2 and Au 8 . • On Ni (111) supported h-BNNS, the O–O bond elongation is maximum on Au 8 cluster. • The presence of Ni(111) support improves the catalytic activity by spin modulation of the B atoms of h-BNNS.