Developing high-efficiency multifunctional electrocatalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) is crucial for advanced electrochemical energy storage and green conversion technologies. Based on density functional theory, the catalytic properties of PtN2 doped single transition metal atoms have been studied comprehensively in this paper. It is noteworthy that Co/VPt-PtN2 and Rh/VPt-PtN2 are potential OER/ORR/HER tri-function electrocatalysts, with an overpotential of 0.29/0.30/−0.17 V and 0.59/0.31/−0.06 V. This electrocatalytic performance is mainly attributed to the optimal electron transfer between the catalyst and the adsorbed intermediate. In addition, the constructed descriptors φ and d-band center (εd) of TM atoms are reliable parameters for evaluating catalytic activity. This study provides an idea for the design of multifunctional electrocatalysts based on low-symmetry pentagonal nanomaterials.