Computational study of structure in transition metal carbides catalytic electrode materials

Computational studies of materials using first-principles methods have many applications related to renewable energy, its storage and conversion. In the present work Density Functional Theory (DFT) used to investigated the Mo₂C catalytic electrode.

Transition metal carbides (TMCs) are an important class of materials that are of a particular interest for catalysis both as catalysts and support materials. Mo₂C is a good support material for the oxygen reduction reaction (ORR) catalysts on fuel cells due to its durability and high electrical conductivity. Recent work: Krishnamurthy, C. et al. J. Phys. Chem. Lett. 9, 2229-2234 (2018), has shown that ultra-low Pt loading in the form of Pt nano-rafts can be obtained on Mo₂C support due to the disordered nature of the C/vacancy arrangement within Mo₂C cell. Therefore, it is necessary to understand the energetics of this system and the factors that control the C/vacancy arrangement is necessary. Motivated by this problem, we established a simple function based on the positions of C atoms and vacancies for the energies of different C/vacancy arrangement based on fundamental properties of the Mo₂C system. This new energy function paves the way for the study of bigger systems (up to million atoms) of Mo₂C without the need to use time-consuming quantum mechanical calculations. As a first demonstration, we have carried out simulations of the C atom arrangement order-disorder phase transition in Mo₂C and Ti₂C carbides and showed that the obtained transition temperatures are in good agreement with experimental data.