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The potential of nitrogen‐doped carbon nanofibers with encapsulated Ni nanoparticles as a bifunctional catalyst in H2 and O2 evolution reactions (HER and OER, respectively) was studied. The proposed heterostructure is fabricated via a facile chemical vapor deposition on Ni supported on graphitic carbon nitride (GCN) as a precursor. HER was an effect of photocatalytic water splitting and catalytic dehydrogenation of lactic acid used as sacrificial electron donor. However, photocatalysis played the dominant role in the acceleration of the reaction rate which was 17 times and 330 times higher in respect to the sample prior the CVD and to pristine GCN, respectively. The catalyst exhibited boosted electrocatalytic activity in OER and outstanding stability in respect to RuO2 in alkaline medium. The overpotentials calculated from linear sweep voltammetry at 10 mA cm−2 is ∼383 mV for the fabricated electrocatalyst in respect to 490 mV for the RuO2 and Tafel slope is calculated to be 106 mV dec−1 in comparison to 136 mV dec−1 for the reference which is above the state‐of the‐art bifunctional catalysts reported to date. The results reveal that the catalytic processes were boosted due to several key effects such as enhanced visible light absorption, better charge carriers transfer and separation, increased free charge carrier concentration and higher reducing ability of electrons. [ABSTRACT FROM AUTHOR]