Highly Efficient ZIF-67-Derived PtCo Alloy–CN Interface for Low-Temperature Aqueous-Phase Fischer–Tropsch Synthesis

Abstract

Designing new materials for selective Fischer-Tropsch synthesis (FTS) is an elegant way to enhance local feedstock utilization like biomass and waste. In this approach, we have designed a thermally and chemically stable bimetallic PtCo/NC hybrid nanocomposite catalyst derived from a zeolitic imidazolate framework (ZIF-67, which contains cobalt as a metal center) through carbonization for low-temperature (413-473 K) aqueous-phase Fischer-Tropsch synthesis (AFTS). The selectivity of the desired range of hydrocarbons is adjusted using a highly dispersed PtCo bimetallic alloy, which facilitates extraordinary reduction of a metal oxide to active species by the synergic effect under the AFTS reaction conditions. The ZIF-derived catalyst tested in this study exhibited the highest activity to date for very low temperatures (433 K) in aqueous-phase Fischer-Tropsch synthesis with CO conversion rates between 0.61 and 1.20 mol_CO·mol_Co^-1·h^-1. Insights of the remarkable catalyst activity were examined by <i>in situ</i> X-ray photoelectron spectroscopy (XPS) studies corroborated by density functional theory (DFT) calculation. The bimetallic Co₃Pt (111) surface was found to be highly active for the C-C coupling reaction between surface-adsorbed C and CO, forming a CCO intermediate with a very low activation barrier (<i>E</i>_a = 0.37 eV), in comparison to the C-C coupling activation barrier obtained over the Co (111) surface (<i>E</i>_a = 0.87 eV). This unique approach and observations create a new path for developing next-generation advanced catalyst systems and processes for selective low-temperature FTS.