Work function of the material is a strong indicator of the state of a surface and its surrounding. Au being an excellent promoter for H₂S, work function changes of pure and Au modified ZnO network films upon exposure to gas have been investigated using Kelvin probe method. Au modified ZnO sample exhibited a work function of 5.42 eV which is ~320 meV higher than that of pure ZnO sample (5.10 eV). This increase could be attributed to the nano-Schottky type of barrier junction formed between Au and ZnO nanowires. Exposure to H₂S resulted in decrease of work function for both pure and Au modified ZnO NWs network films. H₂S being reducing in nature, this decrease can be accounted on the basis of Fermi level shift due to large number of electrons that the gas donates to the matrix upon interaction with adsorbed oxygen species.