Activating transition metal dichalcogenide monolayers as efficient electrocatalysts for the oxygen reduction reaction via single atom doping

Recent studies in 2D transition-metal-dichalcogenides (TMDs) for electrocatalytic applications have mainly concentrated on MoS2, while the catalytic properties of the majority of TMDs with other metal compositions remain uncovered. This work reveals the catalytic activity of sulfur-based ⅣB-ⅦB TMDs in different phase structures (2H, 1T, 1T') for oxygen reduction reaction (ORR). The pristine TMDs are inactive for ORR because of the weak O2 and non-bonded *OOH adsorption over the surface S-layer. The adatom doping with transition metal and non-metal substitutional doping are efficient strategies to activate TMDs with enhanced ORR activity. Among the studied 14 TMDs structures, 1T-TiS2, 2H-TiS2, 1T-ZrS2, 1T-TaS2, 1T-NbS2 and 2H-TaS2 act as feasible ORR electrocatalysts by Ni or Co doping, which exhibit low overpotential (0.32~0.55 V) comparable to the state-of-the-art Pt-based electrocatalysts. While 2H-WS2, 2H-TaS2, 2H-TiS2 and 1T′-WS2 can be effectively activated by N doping with overpotential of 0.3 ~ 0.75 V. Single Fe doping is less effective, due to the larger charge transfer between Fe and TMDs leading to stronger adsorption of *OOH/*OH than Co or Ni. Moreover, single P doping results in very poor ORR performance since the higher location of P occupied states (EP) towards Fermi level causes very strong interaction with oxygen intermediates, making *OH protonation very unfavorable. Our predictions show an effective way to modify ORR activity of TMDs by single atom doping, which would be helpful for the design of high efficient electrocatalysts and provoke future experimental interests of ORR in these systems.