W–N/C@Co9S8@WS2-hollow carbon nanocage as multifunctional electrocatalysts for DSSCS,ORR and OER

Due to the unique characteristics like large specific surface area of Transition Metal Dichalcogenides (TMDs) and its well-defined hollow Metal-Organic Framework (MOF), it is widely used in dye-sensitized solar cells (DSSCs), oxygen reduction (ORR) and oxygen evolution reaction(OER). Herein, we prepare N-doped C hollow metal organic frame structure materials, which are used as a template, WS2 nanocrystals are grown and encapsulated in MOF with interfacial W–N coupling centers. During the pyrolysis, after carbonizing, ZIF-67 becomes Co, N-doped C materials, and the growth of WS2 is effectively suppressed, creating multi-functional groups W–N/C@Co9S8@WS2 materials. The synthesized material is employed as a counter electrode (CE) for dye-sensitized solar cells, its high power conversion efficiency (PCE) (7.38%) based DSSC under AM 1.5G irradiation was much more than that of Pt (7.06%). Such excellent electrocatalytic performance was resulted from the unique frame pore structure, the synergistic effect of WS2, Co9S8 and W–N multi-functional groups. Besides, W–N/C-4@Co9S8@WS2 shows E1/2≈0.84 V and a little Tafel slope of 44 mVdec−1 when employed as electrocatalysts for ORR and potential ≈ 1.79 V to achieve the current density of 10 mA cm−2, which are lower than that of Pt/C ≈ 1.91 V catalysts in 0.1 M KOH.