Nanostructured NiCo2S4@NiCo2O4-reduced graphene oxide as an efficient hydrogen evolution electrocatalyst in alkaline electrolyte

Interface engineering of NiS/NiCo2S4 heterostructure with charge redistribution for boosting overall water splitting

Developing highly efficient bifunctional non-noble metal-based electrocatalysts is pivotal to fulfilling practical water electrolysis. In this work, NiS/NiCo2S4 heterostructured electrocatalysts are prepared through a simply controlling sulfurization process by employing a one-pot solvothermal strategy. The alteration of cobalt addition amount can affect the crystalline phase, morphology, and catalytic activity of the resulting heterostructured materials. The successful integration of NiS with NiCo2S4 is realized by deliberately tuning the cobalt addition amount. The resulting Co-Ni-S5:1 delivers high activity with low overpotentials of 198 and 259 mV to attain 10 mA cm-2 when used as electrocatalysts toward hydrogen evolution reaction and oxygen evolution reaction, respectively. Experimental and theoretical calculations evidence the strong interface coupling between NiS and NiCo2S4 leads to increased electronic conductivity, electron migration near lattice-matched interface and interfacial charge redistribution, thereof enhancing the reaction kinetics rate and activity. Moreover, the potential application is demonstrated by employing Co-Ni-S5:1 in a two-electrode electrolyzer which can efficiently catalyze water electrolysis and work stably for 100 h. This work not only provides highly efficient bifunctional heterostructured electrocatalysts by simply regulating the metal components in sulfides but also further broadens the application of interface engineering.

Graphene-Based Metal-Organic Framework Hybrids for Applications in Catalysis, Environmental, and Energy Technologies

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".

Recent advances in the electrochemical applications of Ni-based metal organic frameworks (Ni-MOFs) and their derivatives

Nickel-based metal-organic skeletal materials (Ni-MOFs) are a new class of inorganic materials that have aroused attention of investigators during past couple of years. They offer advantages such as high specific surface area, structural diversity, tunable framework etc. This assorted class of materials exhibited catalytic activity and electrochemical properties and display wide range of applications in the fields of electrochemical sensing, electrical energy storage and electrocatalysis. In this context, the presented review focuses on strategies to improve the electrochemical performance and stability of Ni-MOFs through the optimization of synthesis conditions, the construction of composite materials, and the preparation of derivatives of precursors. The review also presents the applications of Ni-MOFs and their derivatives as electrochemical sensors, energy storage devices, and electrocatalysts. In addition, the challenges and further electrochemical development prospects of Ni-MOFs have been discussed.

Construction of reduced graphene oxide coupled with CoSe2-MoSe2 heterostructure for enhanced electrocatalytic hydrogen production

It is important to develop novel energy to solve energy shortage and environmental problems. Hydrogen evolution reaction (HER) is envisaged as a viable technology that can be used to develop sustainable clean energy. Herein, we report a catalyst with CoSe₂-MoSe₂ heterostructure grown on reduced graphene oxide with an optimum Co/Mo proportion of 1:1 (CoSe₂-MoSe₂(1-1)/rGO). It exhibits good HER activities in both acidic and alkaline conditions. The CoSe₂-MoSe₂(1-1)/rGO shows an overpotential of 107 mV at 10 mA cm^-2 with a Tafel slope of 56 mV dec^-1 under acidic condition. Meanwhile, CoSe₂-MoSe₂(1-1)/rGO also presents an overpotential of 182 mV at 10 mA cm^-2 and with a Tafel slope of 89 mV dec^-1 under alkaline condition. These impressive performances of the catalyst are mainly due to the excellent electronic transmission capability of rGO and the abundant active sites of CoSe₂-MoSe₂ heterostructure as well as the optimized hydrogen adsorption energy of CoSe₂-MoSe₂ interface. The design of CoSe₂-MoSe₂(1-1)/rGO provides a meaningful guide for manufacturing electrode in energy storage and conversion.

Anchoring Co3S4 nanowires on NiCo2O4 nanosheet arrays as high-performance electrocatalyst for hydrogen and oxygen evolution

The development of catalysts which can substitute expensive metals to efficiently split water is currently a hot research topic. Here, multi-layered NF/NiCo2O4/Co3S4 nanocomposite was prepared on 3D porous nickel foam...