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Facile template–free controllable growth of freestanding polyhedron–like CoS onto microporous Ni foam with three-dimensional architecture via a mild hydrothermal technique is reported. The as-obtained CoS catalyst phase was first tailored to N-Co9S8 (nitrogen doped Co9S8), and its inherent reaction kinetics and conductivity were then enhanced through sulfur incorporation via a hydrothermal process. The electrochemical performance of the pristine CoS and a sulfur-enriched N-Co9S8 (S, N-Co9S8) electrode in alkaline 1.0 M KOH was examined. The optimized polyhedral S, N-Co9S8 structured catalyst exhibits significantly enhanced electrocatalytic activity for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). As a result, low overpotentials of 244 and −92 mV is required to achieve the current density of 10 mA cm−2 for the OER and HER, respectively. Furthermore, when the polyhedral S, N-Co9S8 catalyst was employed as a bifunctional catalyst in a two-electrode electrolyzer cell exhibiting a cell voltage of 1.549 V at 10 mA cm−2 and demonstrates excellent long-term (50 hrs.) chronopotentiometric electrolysis at various current rate, reveals excellent bifunctional OER and HER activities at different applied current densities. The superior OER and HER activities of the S, N-Co9S8 catalyst is result of the improved electronic conductivity and enhanced intrinsic reaction kinetics, which led to the enhanced electrocatalytically active sites after the incorporation of heteroatoms in the catalyst structure.

Commercial lithium–ion batteries (LIBs) are insufficient to bridge the energy density gap between demand and supply in advanced heavy and portable electronic devices because of graphite anodes (poor theoretical capacity: 372 mAh g−1). Ternary chalcogenide metal‐sulfides are promising as alternative anode materials in high power and energy densities but suffer from capacity fading with poor long‐term cycling stability due to the dissolution of polysulfide species created during the lithium‐ion insertion/de‐insertion process. Here, we report the hydrothermal synthesis of graphene integrated CuCo2S4 microparticles as a high‐capacity and sustainable anode material for LIBs. We solve the concentration gradient of lithium polysulfide at the interface of electrode/electrolyte via integrating graphene into the active metal sulfide anode material. The mechanically flexible and highly conductive nature of graphene helps relieve undesirable elongation and shrinkage during battery cycling, suppressing active material dissolution and enhancing electron/ion transport through the electrochemical double‐layer (EDL). Our one step approach demonstrates towards the practical application of advanced metal sulfide anodes for LIBs.