In this study, we successfully manipulate the heterogeneous junction at Co₃O₄-Pt core-shell cathodic nanocatalysts (C/P CNCs) by controlling the core/shell ratios. Our results indicate the cobalt core atoms would inject their valence charge to the surface Pt atoms due to the presence of extensive lattice strain in the shell region. This charge injection accelerates the redox kinetics at the catalysts surface. Consequently, compared with that using Pt nanoparticle cathode, the C/P CNCs at an optimal Pt/Co atomic ratio of 1, improves the current density and the photovoltaic efficiency of dye-sensitized soar cell (DSSC) by ∼36.3% and ∼22.9%, respectively. By combining structure and electrochemical analysis, we systematically elucidate the effects of Pt/Co (shell/core) ratios, the interplay of Co atoms on the shell structures, and the redox activity of C/P CNCs on the DSSC performance. Hereby, this study provide mechanistic insights in developing electrocatalysts for DSSC with programmable performance and reduced Pt utilization.