Engineering the active sites tuned MoS₂ nanoarray structures by transition metal doping for hydrogen evolution and supercapacitor applications

Extensive investigations have been made over the past two decades on the two-dimensional molybdenum sulfide (MoS₂) since their dominating characteristics for the various applications including electrocatalysis and energy storage. Albeit MoS₂ possesses the plentiful active sulfur edges, but their deficient inactive facets lead the poor conductivity and low efficiency. In this work, we attempted to activate more active sites by the insertion of doping transition metals such as nickel (Ni), copper (Cu) and iron (Fe) into MoS₂ matrix. A facile chemical precipitation methodology was used to prepare the greatly active Fe, Cu and Ni metal doped MoS₂ nanoarrays for hydrogen evolution and supercapacitors. Microscopic studies revealed the tuned morphology composed of nanoarrays structured domains of grains for metals doped MoS₂ with the vertically aligned layers and extended layer spacing. The modified morphological properties, enriched surface area and plentiful active edges were apparently established for the metal doped MoS₂. Hydrogen evolution results revealed that the improved electrocatalytic activity for Fe doped MoS₂ nanoarrays with the low overpotentials, small Tafel slopes and unremitting reactions over 24 h in the acid and alkaline solution. The highly porous structured Cu doped MoS₂ nanostructures owned the maximum capacitance of 353 F·g^-1 at 1 A·g^-1 current density with an admirable retaining capacity of ~94% after 5000 cycles.