Mesoporous amorphous Al2O3/crystalline WO3 heterophase hybrids for electrocatalysis and gas sensing applications

Abstract

In this study, a versatile multicomponent co-assembly strategy is developed to rationally construct ordered mesoporous amorphous Al₂O₃/crystalline WO₃ heterophase materials (denoted as mAl₂O₃/WO₃). These materials exhibit excellent performance as electrocatalysts in hydrogen evolution reaction (HER) at high Al₂O₃ contents and as gas sensors in acetone detection at low Al₂O₃ contents. X-ray absorption fine structure spectroscopy reveals an unexpected local phase transition of the framework from γ-WO₃ to metastable ε-WO₃ and lattice distortion, which accounts for their application performances. Compared with commercial WO₃ powders and mesoporous WO₃, the mAl₂O₃/WO₃ hybrid materials exhibit a high cathodic current density of 100 mA cm⁻² at an overpotential of −230 mV and a low Tafel slope (52 mV dec⁻¹), close to that of expensive commercial 20% Pt/C (−219 mV and 48 mV dec⁻¹), and they also possess high alkali-stability for even 10 000 cyclic voltammetric sweeps. Thanks to the synergic effect between the catalytic ability of Al₂O₃ and the strong interfacial interaction of WO₃ toward acetone molecules (a typical biomarker for diabetes), the mAl₂O₃/WO₃ nanocomposites with low contents of Al₂O₃ (<2 wt%) exhibit superior sensing performance toward acetone with excellent selectivity and higher responses even at low concentrations as compared with mesoporous WO₃. The concept about designed synthesis of such mesoporous amorphous/crystalline nanocomposites with dual functions at different content ratios holds great promise in development of novel advanced functional materials.