High-Throughput Approach Exploitation: Two-Dimensional Double-Metal Sulfide (M2S2) of Efficient Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells

A transition-metal sulfide (M2S2) nanolayer as a catalyst for the oxygen reduction reaction (ORR) has been investigated by the density functional theory (DFT) method to explore the underlying mechanisms of the elementary reaction steps for the ORR process. Both the O-2 dissociation and O-2 hydrogenation paths are probably possible in the ORR on the M2S2 surface. All of the possible intermediate reaction steps of the ORR are exothermic for O-2 hydrogenation. This indicates that the four-electron reaction path (4e(-) ORR) process is the most favorable path, and it is preferred over the two-electron path (2e(-) ORR) process. The changes in the reaction free energy diagrams were determined, and these diagrams showed that oxygen hydrogenation (OOH) is the rate-determining step. Meanwhile, different working potentials for our studied catalysts were also considered, and we observed that the double-transition-metal sulfide catalysts are energetically favorable (exothermic) catalysts via a 4e transfer mechanism of the ORR processes. According to the formation energies of the ORR intermediates (*O, *OH, *OOH) and the scaling relations between them on different slabs, the volcano plot for the overpotential of the catalyst is also an important index of the catalytic activities, and we found that a smaller overpotential is appropriate to determine better catalytic activities for the ORR process.