The present development gives an insight into the effect of the distribution of bimetallic sites in denitrification. A highly-dispersed Pd-Cu bimetallic catalyst supported by titanium dioxide nanofibers (Pd-Cu/TiO2) was in situ fabricated by electrospinning and subsequent calcination and chemical reduction, and then applied in the catalytic reduction of water phase nitrate (NO3) to nitrogen gas (N-2). Compared with ex situ Pd-Cu impregnated catalyst, the in situ Pd-Cu/TiO2 nanofibers exhibited the high nitrate removal efficiency, selectivity and fast kinetics (about twice that of impregnated ones). These good catalytic performances are mainly benefited from increased active sites and raised ratio of nitrogen to hydrogen on them, which are brought about by the well-dispersed and closely connected Pd-Cu bimetallic nanoparticles in TiO2 nanofiber matrix. Moreover, the in situ nanofiber matrix provides a physical barrier to inhibit bimetallic nanoparticles movement, aggregation and leakage from the support into water, and hence significantly enhances the recyclability for nitrate reduction. (C) 2017 Elsevier B.V. All rights reserved.