Effective adsorption and speedy surface reactions are vital requirements for efficient active sites in catalysis, but it remains challenging to maximize these two functions simultaneously. We present a solution to this issue by designing a series of atom-pair catalytic sites with tunable electronic interactions. As a case study, NO selective reduction occurring on V1-W1/TiO2 is chosen. Experimental and theoretical results reveal that the synergistic electron effect present between the paired atoms enriches high-energy spin charge around the Fermi level, simultaneously rendering reactant (NH3 or O2) adsorption more effective and subsequent surface reactions speedier as compared with single V or W atom alone, and hence higher reaction rates. This strategy enables us to rationally design a high-performance V1-Mo1/TiO2 catalyst with optimized vanadium(IV)-molybdenum(V) electronic interactions, which has exceptional activity significantly higher than the commercial or reported catalysts.