Defect engineering in heterostructured carbon-based electrode materials has evolved as an emerging strategy to boost the electrocatalytic activity. Herein, a facile single-step route is reported to synthesize novel N-coordinated bimetal doped graphitic carbon (Mn/Co-NGC). The formation of M(Mn, Co)-N-C in the catalyst (Mn/Co-NGC) significantly accelerated the triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). The electrocatalyst provided the synergistic effect of bimetal (Mn, Co)-N active-sites within graphitic-carbon framework, which promoted the conductivity and efficient charge transfer via multiple channels to enhance the IRR and HER. Therefore, as IRR electrocatalyst, Mn/Co-NGC equipped solar-cell attained a superior effi-ciency of 8.05% compared to Pt (6.82%). The electrocatalyst also exhibited an impressive potential towards HER, providing a low overpoential of 116 mV at 10 mA cm(-2) and Tafel slope of 58 mV dec(-1). Moreover, Mn/Co-NGC based solar-cell demonstrated superior stability with 99% efficiency retention (7.96% / 8.05%) after 50 redox-cycles for IRR, and a negligible change in overpotential after 1000 CV cycles. The intrinsic catalytic mechanism of electrocatalysts is studied by insighting their electronic structures, work functions, bonding, and ion-adsorption behaviors, using first-principle DFT-calculations. The current study leads towards designing highly efficient and cost-effective multifunctional electrocatalysts for advanced energy conversion technologies.