Ammonia electrolysis is a promising technology to obtain green hydrogen with zero-carbon emission, in which ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) occur at the anode and cathode, respectively. However, the lack of efficient catalysts hinders its practical application. Herein, PtZn alloy is combined with Nb2O5 to construct a bifunctional heterostructure catalyst (PtZn-Nb2O5/C). The optimal sample with Nb2O5 content of 7.05 wt % demonstrates the best performance with a peak current density of 304.1 mA mg-1Pt for AOR, and it is only reduced by 17.0% after 4000 cycles of durability tests. For HER, it has a low overpotential of 34 mV at -10 mA cm-2 under the alkaline condition. This can be ascribed to the interfacial interaction between the PtZn alloy and Nb2O5, which adjusts the adsorption behavior of OHad to concurrently promote AOR and HER activity. This work thus proposes a viable strategy to design an efficient bifunctional catalyst for hydrogen generation from ammonia electrolysis.