Polyoxometallates@zeolitic-imidazolate-framework derived bimetallic tungsten-cobalt sulfide/porous carbon nanocomposites as efficient bifunctional electrocatalysts for hydrogen and oxygen evolution

Abstract Hydrogen is one of the most promising sustainable energy among numerous new energy resources. Electrocatalytic water splitting for H2 generation is a clean and sustainable approach due to the use of widely existed water as resource. The searching for efficient and low-cost non-precious metal based electrocatalysts for water splitting, including both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), still remains a great challenge. In this work we report a simple method that utilizes the one-pot in-situ synthesized POMs@ZIFs (POMs = Polyoxometallates, ZIFs = Zeolitic imidazolate frameworks) as precursor for the production of WS2/Co1-xS/N, S co-doped porous carbon nanocomposite as efficient electrocatalysts. These precursors POMs@ZIFs can effectively prevent the agglomeration of metal compound particles during heat treatment and leads to homogeneous dispersion of metal active sites within carbon matrix. The resulting bimetallic Co–W sulfide/heteroatom doped porous carbon composites show significant improvement in electrocatalytic activity towards both OER (Tafel slop of 53 mV dec−1 with overpotential of 0.365 V @10 mA cm−2 current density in 1 M KOH media) and HER (Tafel slop of 64 mV dec−1 with overpotential of 0.250 V @10 mA cm−2 current density in 0.5 M H2SO4 solution). This work opens up a new way to obtain low cost bifunctional electrocatalysts towards both OER and HER in water splitting.