Promoting the surface catalytic oxidation activity of MOF-derived Co3O4 rectangular rods via Cr-doping for ppb-level xylene detection

Abstract

Promoting the surface catalytic oxidation activity of Co3O4, can contribute the efficient detection of trace reactive gas (eg. xylene), yet certain challenge remains. In this work, a strategy is proposed through incorporating Cr3+ into metal-organic framework (MOF)-templated Co3O4 rectangular rods to substitute Co2+. The optimized sample (Co3O4 with 3 at% Cr-doping) features an increased Co3+/Co2+ ratio, total percentage of reactive oxygen species (surface chemisorbed oxygen, and oxygen vacancies), and high surface area relative to that of the pure Co3O4. In-situ DRIFTS analysis also demonstrates that the Cr-doping can accelerate the fast catalytic oxidation xylene over Co3O4 surface. Consequently, this 3 at% Cr-Co3O4 gas sensor presents a high response (Rg/Ra=33.2@100 ppm), and obvious selectivity to xylene at low working temperature of 130 oC. Moreover, it attains a detection threshold as minimal as 0.1 ppm, surpassing many recent reports. This study announces a robust strategy involving active catalytic oxide towards ppb-level low reactive gas detection for early warning.