Ni x S y /NiSe 2 Hybrid Catalyst Grown In Situ on Conductive Glass Substrate as Efficient Counter Electrode for Dye-Sensitized Solar Cells

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.

Ultrathin Ti3C2Tx (MXene) Nanosheet-Wrapped NiSe2 Octahedral Crystal for Enhanced Supercapacitor Performance and Synergetic Electrocatalytic Water Splitting

Metal selenides, such as NiSe₂, have exhibited great potentials as multifunctional materials for energy storage and conversation. However, the utilization of pure NiSe₂ as electrode materials is limited by its poor cycling stability, low electrical conductivity, and insufficient electrochemically active sites. To remedy these defects, herein, a novel NiSe₂/Ti₃C₂T_x hybrid with strong interfacial interaction and electrical properties is fabricated, by wrapping NiSe₂ octahedral crystal with ultrathin Ti₃C₂T_x MXene nanosheet. The NiSe₂/Ti₃C₂T_x hybrid exhibits excellent electrochemical performance, with a high specific capacitance of 531.2 F g^-1 at 1 A g^-1 for supercapacitor, low overpotential of 200 mV at 10 mA g^-1, and small Tafel slope of 37.7 mV dec^-1 for hydrogen evolution reaction (HER). Furthermore, greater cycling stabilities for NiSe₂/Ti₃C₂T_x hybrid in both supercapacitor and HER have also been achieved. These significant improvements compared with unmodified NiSe₂ should be owing to the strong interfacial interaction between NiSe₂ octahedral crystal and Ti₃C₂T_x MXene, which provides enhanced conductivity, fast charge transfer as well as abundant active sites, and highlight the promising potentials in combinations of MXene with metal selenides for multifunctional applications such as energy storage and conversion.

Enhanced electrocatalytic performance of nickel diselenide grown on graphene toward the reduction of triiodide redox couples

The promising activity of nickel diselenide (NiSe₂) towards electrocatalysis has made it especially attractive in energy conversion fields. However, NiSe₂ with high electrocatalytic performance always requires complicated fabrication or expensive conductive polymers, resulting in the scale-up still being challenging. Herein, we introduce a simple and cost-effective synthesis of NiSe₂ dispersed on the surface of graphene (NiSe₂/RGO NPs). NiSe₂/RGO NPs exhibited enhanced electrocatalytic performance and long-term stability for the reduction reaction of triiodide redox couples in dye-sensitized solar cells (DSSCs). Leveraging the advantageous features, the DSSC fabricated with NiSe₂/RGO NPs as CE had a smaller charge-transfer resistance (R_ct) value and higher short-circuit current density and fill factor than naked NiSe₂ NPs. Additionally, NiSe₂/RGO NPs achieved a PCE of 7.76%, higher than that of pure NiSe₂ (6.51%) and even exceeding that of Pt (7.56%). These prominent features demonstrated that the NiSe₂/RGO NPs in this work are a promising cheap and efficient electrocatalyst to replace state-of-the-art Pt.

The promising activity of nickel diselenide (NiSe₂) towards electrocatalysis has made it especially attractive in energy conversion fields.