Coinage metals doped 1T' WS2 as efficient bifunctional electrocatalyst towards ORR and HER: A first principles study

The electrocatalytic activities of Cu, Ag and Au doped 1T & PRIME; WS2 as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic medium are explored by means of first principles calculations. The stability of these doped systems are inspected in terms of formation energy and charge transfer analysis upon doping. Highest amount of charge transfer towards the dopant is observed for systems with lowest formation energy. For all the doped systems, charge is transferred to the dopant that substitutes the anionic S atom validating the doping scheme and stability of the doped systems. ORR proceeds only via the energetically efficient four electron pathway on Cu doped 1T & PRIME; WS2 with a monotonically exothermic free energy profile. In the case of Ag and Au doped structures, ORR occurs competitively via both two and four electron pathways due to the marginal free energy difference in the 2nd protonation step between these two pathways and produces both H2O or H2O2 competitively as the end product. Study of the effect of electrode potential variation on the free energy profiles reveals the overpotential for ORR on Cu, Ag and Au doped 1T & PRIME; WS2 to be 0.85 V, 0.80 V and 0.66 V respectively via the four electron pathway. Proneness of Cu doped 1T & PRIME; WS2 towards only the four electron pathway and low overpotential for ORR makes it the promising cathode electrocatalyst for ORR among the considered systems. Further study of the HER activity of Cu, Ag and Au doped 1T & PRIME; WS2 reveals the Gibbs free energy of H+ ion adsorption on Cu doped 1T & PRIME; WS2, Ag doped 1T & PRIME; WS2 and Au doped 1T & PRIME; WS2 to be -0.14 eV, -0.17 eV and 0.18 eV respectively indicating high efficiency of those system towards HER in acidic medium.

Automated summary

These calculations study the electrocatalytic activities of Cu, Ag, and Au-doped 1T & PRIME; WS2 as catalysts for ORR and HER in acidic medium. The stability of the doped systems is explored through formation energy and charge transfer analysis. Cu-doped 1T & PRIME; WS2 shows the highest charge transfer and only proceeds through the energetically efficient four-electron pathway for ORR. Ag and Au-doped structures compete in both the two and four-electron pathways, producing H2O or H2O2 as the end product. Cu-doped 1T & PRIME; WS2 is found to be the most promising cathode electrocatalyst for ORR due to its exclusive reliance on the four-electron pathway and low overpotential.