Nanoparticles of ZnO-Chitosan (Zn-Chit) composite were prepared using precipitation methods. Several analytical techniques, such as scanning electron microscope (SEM), transmitted electron microscope (TEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal analysis, were used to characterize the prepared composite. The activity of the modified composite was investigated for nitrite sensing and hydrogen production applications using various electrochemical techniques. A comparative study was performed for pristine ZnO and ZnO loaded on chitosan. The modified Zn-Chit has a linear range of detection 1–150 µM and a limit of detection (LOD) = 0.402 µM (response time ~3 s). The activity of the modified electrode was investigated in a real sample (milk). Furthermore, the anti-interference capability of the surface was utilized in the presence of several inorganic salts and organic additives. Additionally, Zn-Chit composite was employed as an efficient catalyst for hydrogen production in an acidic medium. Thus, the electrode showed long-term stability toward fuel production and enhanced energy security. The electrode reached a current density of 50 mA cm−2at an overpotential equal to −0.31 and −0.2 V (vs. RHE) for GC/ZnO and GC/Zn-Chit, respectively. Electrode durability was studied for long-time constant potential chronoamperometry for 5 h. The electrodes lost 8% and 9% of the initial current for GC/ZnO and GC/Zn-Chit, respectively.