MoO3-CuS p-n heterojunction nanocomposites were synthesized using a one-step, fully aqueous method with pomegranate peel extract, which acted as the reducing, complexing, and stabilizing agent during the entire process. The MoO3-CuS (1:1) nanocomposites that were made had an amazing chemiresistive response of 2400% to 10 vol% H2 at 350 ◦C (with estimated SD ≈ ±0.3% from stable region). The response time was 260 s and the recovery time was 280 s. The sensor exhibited significant selectivity towards prevalent VOCs, dependable functionality at 35% relative humidity, and performance exceeding that of other documented noble-metal-free metal-oxide H2 sensors in the high-concentration range (>10% H2). The exceptional sensing performance is ascribed to the elevated concentration of oxygen-vacancy defects in MoO3, catalytic spillover phenomena from CuS, and effective regulation of the charge-depletion layer at the p-n junction interface. This environmentally friendly way of using technology helps turn biomass waste into nanomaterials that can be used for many different things. This makes it easy, possible, and cheap to get to hydrogen gas sensing technology. The sensor works best at 350 ◦ C, which is a good middle ground for monitoring high concentrations of H2 and shows ways to make it work better at lower temperatures in the future.
