ZIF-67 Derived Cu-Co Mixed Oxides for Efficient Catalytic Oxidation of Formaldehyde at Low-Temperature

Abstract

It is still an intractable problem to exploit high-efficient Co-based catalysts for low-temperature HCHO oxidation. Herein, we synthesized a series of Cu-doped Co3O4 catalysts (Cu1Co8, Cu1Co4, and Cu1Co2 corresponded to 1/8, 1/4, and 1/2 of Cu/Co molar ratios, respectively) via in situ pyrolysis of bimetal Cu-ZIF-67 precursors and the pure Co3O4 sample was also prepared through directly annealing monometal ZIF-67 for comparison. Performance tests of HCHO oxidation found that Cu doping remarkably enhanced the low-temperature HCHO oxidation performance of Co3O4 sample, and thereinto the Cu1Co4 possessed the optimal HCHO oxidation activity, which achieved 90% HCHO conversion at 108 °C. The characterization results revealed that the stronger interaction between Cu and Co species (Co2+ + Cu2+ ↔ Co3+ + Cu+) of Cu1Co4 not only facilitates the formation of defect sites, Co3+ and surface adsorbed oxygen species but also improves its low-temperature reducibility, and consequently resulting in its superior HCHO oxidation performance. Furthermore, the in-situ DRIFTS results suggested that the formaldehyde oxidation over Cu1Co4 followed HCHO → H2CO2 → HCOO− → CO32− → CO2 pathway. The present work provides a novel and facile approach to fabricating highly effective Co-based catalysts for low-temperature HCHO oxidation.