Enhancing ethylene glycol gas sensor performance through the synergistic effects of NiO-ZnO p-n heterojunctions using maize straw bio-templates

Ethylene glycol is a widely used colorless organic solvent that poses potential risks to both environmental safety and human health, making its reliable detection highly important. In this research, a hierarchical porous structure of NiO-ZnO templated by maize straw (STHPS NiO-ZnO) was fabricated by integrating the hydrothermal method with a biotemplating approach. At 100°C, STHPS NiO-ZnO shows a high response of 135 toward 100 ppm ethylene glycol, a measurable response at concentrations as low as 0.5 ppm, excellent selectivity, and enhanced stability (with a mean deviation of less than 4%). To investigate the synergetic effect of heterojunctions and maize straw biotemplate on gas-sensing performance, ZnO and NiO-ZnO were prepared using a hydrothermal approach. In contrast to pure ZnO, the NiO-ZnO heterojunction shows enhanced ethylene glycol sensing at lower operating temperatures (100°C/200°C), higher response (75/19) to 100 ppm ethylene glycol, improved selectivity, and a lower detection limit (3 ppm/10 ppm). Furthermore, the gas sensing performance of STHPS NiO-ZnO is further improved compared with NiO-ZnO. From characterization tests and mechanism analysis, the superior gas-sensing performance of STHPS NiO-ZnO is attributed to the synergetic effect of the p-n heterojunction and the maize straw biotemplate. Therefore, the work presents an innovative strategy for the preparation of high-performance ethylene glycol gas-sensing materials by introducing a bio-template into heterojunctions.