Exploring calcium tantalates and niobates as prospective catalyst supports for water electrolysis

In an attempt to identify new electrochemically stable catalyst supports for electrolysis of water, the electronic structures of CaNb2O6, CaTa2O6, Ca2Nb2O7, and Ca2Ta2O7 compounds doped with small amounts of elements from 3A, 3B, 5B, and 6A groups of the Periodic table as well as F from group 7B have been calculated using the Vienna Ab-initio Simulation Package (VASP), within the projector augmented-wave (PAW) method in the general gradient approximation (GGA) for conducting the exchange-correlation corrections. The role of incorporating the additional elements in improving the electronic conductivity as well as the structural and chemical stability is discussed. Based on the calculated values of the cohesive energies for the materials and their type of electronic conductivity, we hypothesize that group 3A elements (Sc and Y) as well as F-doping contribute drastically to the improvement of the electronic properties as well as the chemical stability of all four calcium tantalates/niobates parent oxides. The study indicates that these doped compounds might therefore serve as the most appropriate candidates for use as catalyst supports in water electrolysis.

► Ab initio study of doped Ca-niobates and tantalates has been conducted.
► Dopants from 3A, 3B, 5B, 6A and 7B groups of the Periodic Table have been chosen.
► All dopants improve electronic conductivity of parent oxides, although differently.
► Dopants from 3A, 5B and 7B groups render the oxides metallic.
► Sc and Y dopants improve the conductivity and stability better than other elements.