Local Atomic Environment of Single-Atom Pt in Metallic TMDC Nanosheets Boosts Catalytic Performances of Li-O₂ Batteries

2D Transition metal dichalcogenides (TMDCs) show changeable electronic properties corresponding to the polytype and chemical modification at the atomic level of 2D TMDCs. Metallic TMDCs comprising the trigonal structure (1T or 1T’ phase) have been investigated as efficient catalysts due to their proper electrochemical properties compared to semiconducting TMDCs with the 2H phase. These metallic TMDCs catalysts have been prepared by atomic-scale chemical modifications such as single-atom doping. However, a detailed role of single-atom doping in TMDCs is still ambiguous because it is unclear that the enhanced catalytic activities stem from whether the metallic properties or electrochemical properties of single-atom.<br/>Here, we report the facile one-pot synthesis of metallic WSe₂ few-layer nanosheets. Subsequent solution treatments at room temperature enabled isolated incorporation of single atoms such as Rh, Pd, Ir, and Pt into metallic WSe₂ nanosheets. Extensive experimental analysis reveals that considerably high Pt content (~5 wt%) was doped in metallic WSe₂ nanosheets (Pt_SA-WSe₂). Local atomic structure of Pt_SA-WSe₂ was proved through X-ray analysis including XPS and XPDF, which supports that single-atom Pt is individually distributed inside of WSe₂. For efficient Li-O₂ batteries, cathode materials are required to overcome the sluggish kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Pt_SA-WSe₂ shows enhanced ORR/OER activities by dissociative oxygen adsorption on the W sites of the basal planes as well as single-atom Pt sites in metallic WSe₂, which is demonstrated through experimental analysis and DFT calculations as well. Eventually, Pt_SA-WSe₂ shows the enhanced Li-O₂ battery performances with the capacity of 27,000 mAhg^-1 and stable discharge/charge cycles of 350.