MOF-derived nickel−cobalt bimetal oxide nanostructures as a cooperative catalyst for the reduction of 4-nitrophenol

BACKGROUND 4-Nitrophenol, as a representative hazardous contaminant, may pose potential risks to the environment in the process of production, storage, and use. Catalytic hydrogenation reduction offers a promising route to the removal of 4-nitrophenol by its transformation into the less toxic and biodegradable 4-aminophenol. In this work, nickel−cobalt bimetal oxide nanostructures were fabricated by the thermal decomposition of metal organic frameworks and cooperatively utilized for the catalytic reduction of 4-nitrophenol. RESULTS The as-fabricated oxide catalysts were characterized and analyzed with several physicochemical measurements, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, Fourier-transform infrared spectroscopy, Raman spectroscopy, nitrogen adsorption, and electrochemical impedance spectroscopy. The catalytic reduction of 4-nitrophenol was conducted in the presence of the as-prepared oxide nanostructures with varying Ni/Co ratios to evaluate their catalytic activity. The optimal catalyst (Ni–Co–O) delivered the activity parameter of k’ app = 12.0 min −1 mg −1 , which was higher than either NiO (2.4 min −1 mg −1 ) or Co 3 O 4 (3.6 min −1 mg −1 ). Moreover, the induction time of the 4-nitrophenol reduction was significantly reduced by using the bimetal oxide catalyst. Based on the surface and electrochemistry analyses, the enhancement of catalytic activity for the Ni–Co bimetal oxide nanostructures was discussed. CONCLUSION The above results indicated that the cooperation of nickel with cobalt into bimetal oxide nanostructures exhibited an enhanced catalytic activity, which not only promoted the conversion rate of 4-nitrophenol, but also shortened the reduction induction period.