A metal oxide heterostructure includes mixing a first precursor and a second precursor to form a precursor aqueous mixture, adding at least one constituent to the precursor aqueous mixture to form a first solution, adding a nanostructuring reagent to the first solution to form a second solution, sonochemically treating the second solution to provide a metal oxide powder, filtering, washing, and drying the metal oxide powder to provide a metal oxide nanocomposite heterostructure for a sensing layer of a hydrogen sulfide sensor. A method for forming a hydrogen sulfide sensor includes the metal oxide heterostructure, forming a sensing material, contacting the sensing material with interdigitated electrodes to form a sensing layer, and thermally consolidating the sensing layer to form the hydrogen sulfide sensor.