Controlling the growth of activated carbon supported nickel phosphide catalysts via adjustment of surface group distribution for hydrodeoxygenation of palmitic acid

Abstract

Nickel phosphides were known to be promising substitute for noble metal used in various catalysts. The traditional method of controlling the growth of nickel phosphide species, including Ni2P, Ni3P, and Ni12P5, was either modulating Ni/P molar ratio or changing support. Here, we report a new method to control the growth of nickel phosphide species by tuning the types of surface oxygenated group types on activated carbon. The pretreatment of activated carbon with HNO3 remarkably increased the content of OCO groups. In the preparation process of activated carbon supported nickel phosphide catalyst, the OCO groups might interact with P to form POCO groups. The formed POCO inhibited the reduction of P species at low temperature, and thus inhibited the formation of the nickel phosphides; whereas at 873 K reduction, the formation of pure Ni2P on activated carbon was enhanced. However, the content of -OH groups content increased on activated carbon treated by NH3∙H2O, which might be favorable for the simultaneous formation of Ni2P and Ni12P5 with 1/1 ratio, and the thus formed catalyst displayed excellent catalytic hydrodeoxygenation activity for palmitic acid. Our results demonstrated how simple base and acid pretreatment could be used to tune the interfacial group distribution, hereby providing a strategy to rationally design transition metal phosphide supported catalysts.