Single-Atoms Catalysts based on MXenes

Abstract

Heterogeneous catalysis is crucial on the development of chemical products in industrialized societies. A great deal of major industrial chemical transformations involves heterogeneous catalysts, which are typically comprised of transition metals and metal oxides as substrates. Two-dimensional metastable transition-metal carbides and nitrides, known as MXenes, have garnered increasing attention for nearly a decade because of their versatile composition and structure, stability under certain conditions of interest in catalysis, and numerous appealing properties. The synthesis of Singe-atom Catalyst (SACs) is one of the main active areas in heterogeneous catalysis with the ultimate goal of promoting small-size metal particles as Sisngle Atoms (SAs). Thus, the search for appropriate substrate for SACs is highly demanded for the next generation of heterogeneous catalysis. The present study aims at introducing low-dimensional transition metal carbides as feasible substrates for anchoring single metal atoms by using first-principles based on density functional theory (DFT), calculations. In particular, we focussed on the 4d transition metal atoms (TMs) and nine bare MXene surfaces with M2C stoichiometry (M= Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). The adsorption energies of four different active sites were studied to find the most stable site, HM, and the situation where the SA isolation would be thermodynamically favourable. This energetic parameter is used to find a correlation with respect to structural features such as the atomic height over the MXene surface, the MAX exfoliation energies, and by comparing 4d with 3d TMs. In addition, few TMs from Pt-group plus Au are also investigated in this project. The results show, shortly, that Pt and Au are better dispersed than Pd and Ag and all the 5d TMs are more prone to be isolated with the V2C MXene