AUTHOR=Mpanza Thokozani , Ogundipe Sunday A. , Ndlangamandla Ceboliyozakha L. , Swart Hendrik C. , Nkosi Steven S. 

TITLE=The effect of acids precipitants on the synthesis of WO3 hierarchical nanostructures for highly selective and sensitive H2S detection

JOURNAL=Frontiers in Sensors

VOLUME=4

YEAR=2023

URL=https://www.frontiersin.org/journals/sensors/articles/10.3389/fsens.2023.1143080

DOI=10.3389/fsens.2023.1143080

ISSN=2673-5067

ABSTRACT=<p>The detection and monitoring of H<sub>2</sub>S gas at high and lower concentrations is very crucial since this gas is highly toxic and can affect tissues and organs, especially in occupational environment. This work reports on the synthesis of WO<sub>3</sub> nanostructures-based sensors for highly sensitive and selective H<sub>2</sub>S detection at low operating temperatures. These WO<sub>3</sub> nanostructures were synthesized using pressurized hydrothermal process. Different acids from weak to strong (HNO<sub>3</sub>, H<sub>2</sub>SO<sub>4</sub>, and HCl) were employed as precipitants to form supposedly hierarchical and cube-like nanostructures of WO<sub>3</sub>. These WO<sub>3</sub> nanostructures were characterized by XRD, SEM, TEM, XPS and BET analysis. The fabricated WO<sub>3</sub> sensors were exposed to different target gases (CO<sub>2</sub>, H<sub>2</sub>, CH<sub>4</sub>, NH<sub>3</sub>, LPG and H<sub>2</sub>S) at different concentrations. They were found to be selective to H<sub>2</sub>S, and the WO<sub>3</sub> precipitated by HCl otherwise referred to as WO<sub>3</sub>-HCl was found to be highly sensitive, with high response of S = 1394.04 towards 150 ppm of H<sub>2</sub>S at 125°C operating temperature. The WO<sub>3</sub> precipitated by H<sub>2</sub>SO<sub>4</sub> named WO<sub>3</sub>-H<sub>2</sub>SO<sub>4</sub> showed a high response of 141.64 at 125°C operating temperature. Lastly, WO<sub>3</sub> precipitated by HNO<sub>3</sub> called WO<sub>3</sub>-HNO<sub>3</sub>, recorded a H<sub>2</sub>S response of 125.75 also at 125°C operating temperature. The HCl-precipitated WO<sub>3</sub> is a promising candidate for selective detection of H<sub>2</sub>S, being the most sensitive in the series.</p>