A Co–N–C catalyst modified by alkaline additives for hydrogenation

Abstract

The development of M–N–C catalysts (M = Fe, Co, Ni, etc.) has been hindered by a poor distribution of metal species and large particle size. In this work, alkaline additives were introduced during the precursor synthesis stage to regulate the distribution of metal components. Through hydrothermal and pyrolysis methods, Co–N–C catalysts (Co–N–C–NH₃, Co–N–C–CO₃, and Co–N–C–OH) were synthesized using folic acid as the carbon and nitrogen source, cobalt chloride as a metal salt, and ammonia solution, sodium carbonate solution, and sodium hydroxide solution as alkaline additives, respectively. The influence of different alkaline additives on the morphology, composition, and structure of the Co–N–C catalysts was analyzed using various characterization methods. The results indicated that the Co–N–C–CO₃ catalyst prepared using sodium carbonate solution has the largest specific surface area, and the smallest and most evenly distributed Co nanoparticles. Moreover, the catalytic activity of the prepared Co–N–C catalysts in the hydrogenation of nitrobenzene was evaluated, and the influence of alkaline additives on their catalytic performance was further explored. Among them, the Co–N–C–CO₃ catalyst achieved the best performance in the hydrogenation of nitrobenzene after reaction at 110 °C and under 1 MPa of hydrogen for 3 h, with a nitrobenzene conversion rate of over 99%. Comparative experiments confirmed that Co nanoparticles and Co–N_x sites constituted the active centers of the catalytic reaction. This strategy provides theoretical support and a practical basis for optimizing the performance of Co–N–C catalysts.