Tuning electronic structure of hedgehog-like nickel cobaltite via molybdenum-doping for enhanced electrocatalytic oxygen evolution catalysis.

As a typical spinel oxide, nickel cobaltite (NiCo2O4) is considered to be a promising and reliable oxygen evolution reaction (OER) catalyst due to its abundant oxidation states and the synergistic effect of multiple metal species. However, the electrocatalytic OER performance of NiCo2O4 has always been limited by the low specific surface area and poor intrinsic conductivity of spinels. Herein, the hedgehog-like molybdenum-doped NiCo2O4 (Mo-NiCo2O4) catalyst was prepared as an efficient OER electrocatalyst via a facile hydrothermal method followed with high-temperature annealing. The Mo-NiCo2O4-0.075 with Mo doping concentration of âˆ¼ 1.95 wt% exhibits excellent OER performance with a low overpotential of 265 mV at a current density of 10 mA·cm-2and a Tafel slope of 126.63 mV·dec-1, as well as excellent cyclingstability.The results demonstrated that the hedgehog-like structure provides Mo-NiCo2O4 with the high surface area and mesopores that enhance electrolyte diffusion and optimal active site exposure. The in-situ Raman spectra and density functional theory calculations show that the Mo cations doping improve the intrinsic conductivity of the NiCo2O4 while modulating the chemisorption of intermediates. Meanwhile, the energy barriers of *OH and O* formation decrease significantly after Mo doping, effectively facilitating water dissociation and optimizing the reaction kinetics.

Interface Coordination Engineering of P-Fe3O4/Fe@C Derived from an Iron-Based Metal Organic Framework for pH-Universal Water Splitting.

Developing electrocatalysts with high energy conversion efficiency is urgently needed. In this work, P-Fe3O4/Fe@C electrodes with rich under-coordinated Fe atom interfaces are constructed for efficient pH-universal water splitting. The introduction of under-coordinated Fe atoms into the P-Fe3O4/Fe@C interface can increase the local charge density and polarize the 3d orbital lone electrons, which promotes water adsorption and activation to release more H*, thus elevating electrocatalytic activity. As a donor-like catalyst, P-Fe3O4/Fe@C displays excellent electrocatalytic performance with overpotentials of 160 mV and 214 mV in acidic and alkaline electrolytes at 10 mA cm-2, in addition to pH-universal long-term stability.

Photo-Cross-Linked Polymeric Dispersants of Comb-Shaped Benzophenone-Containing Poly(ether amine).

Efficient dispersion of nanoparticles (NPs) is a crucial challenge in the preparation and application of composites that contain NPs, particularly in coatings, inks, and related materials. Physical adsorption and chemical modification are the two common methods used to disperse NPs. However, the former suffers from desorption, and the latter is more specific and has limited versatility. To address these issues, we developed a novel photo-cross-linked polymeric dispersant, comb-shaped benzophenone-containing poly(ether amine) (bPEA), using a one-pot nucleophilic/cyclic-opening addition reaction. The results demonstrated that the bPEA dispersant forms a dense and stable shell on the surface of pigment NPs through physical adsorption and subsequent chemical photo-cross-linking, which effectively overcome the drawbacks of the desorption occurred in physical adsorption and the specificity of the chemical modification. By means of the dispersing effect of bPEA, the obtained pigment dispersions show high solvent, thermal, and pH stability without flocculation during storage. Moreover, the NPs dispersants show good compatibility with screen printing, coating, and 3D printing, endowing the ornamental products with high uniformity, color fastness, and less color shading. These properties make bPEA dispersants ideal candidates in fabrication dispersions of other NPs.

Dual Confinement of CoSe2 Nanorods with Polyphosphazene-Derived Heteroatom-Doped Carbon and Reduced Graphene Oxide for Potassium-Ion Batteries.

High-capacity and highly stable anode materials are some of the keys to the realization of the application of potassium-ion batteries (PIBs). Cobalt diselenide (CoSe2) has been regarded as a high-potential anode material for PIBs. However, solving the problems of sluggish kinetics and large volumetric expansion during intercalation/deintercalation of K+ ions is always very challenging in terms of cobalt diselenide-based anode materials. Herein, reduced graphene oxide-encapsulated polyphosphazene-derived S, P, and N codoped carbon (SPNC)-coated CoSe2 nanorods (CoSe2⊂SPNC⊂rGO) were designed as PIB anode materials. CoSe2⊂SPNC⊂rGO delivers an excellent reversible capacity of 287.2 mAh g-1 at 100 mA g-1. Benefiting from the coating of heteroatom-doped carbon and encapsulation of rGO, the CoSe2⊂SPNC⊂rGO anodes exhibit a remarkable rate capability (100-1500 mA g-1 current density) and high stability (208.8 mAh g-1 after 500 cycles at 500 mA g-1). The results demonstrate that S, P, and N codoping in carbon layers provides active sites for K+ ion storage and increases the electrical conductivity. More importantly, the dual confinement of CoSe2 nanorods with carbon layers and rGO significantly reduced the volume expansion and kept the electrode structural integrity with repeating intercalation/deintercalation of K+ ions.

Rod-like nickel doped Co3Se4/reduced graphene oxide hybrids as efficient electrocatalysts for oxygen evolution reactions.

In the oxygen evolution reaction (OER), highly active catalysts are essential for reducing the overpotential and improving the slow kinetics of the process. Cobalt selenide (Co3Se4) has always been considered as a promising electrocatalyst for the OER due to the well-suited electronic configuration of the Co ions in it. However, poor exposure of the active sites and low electron conductivity are still its biggest problems. In this study, we report an efficient Ni-doped rod-like Co3Se4 hybridized with reduced graphene oxide (Ni-Co3Se4/rGO) as an OER electrocatalyst. The Ni doping regulates the electronic structure of Co3Se4 and significantly reduces the overpotential of Co3Se4 toward the OER under alkaline conditions. Simultaneously, hybridization of the reduced graphene oxide (rGO) enhances the conductivity which leads to the improvement in OER activity. The Ni-Co3Se4/rGO catalyst shows a lower overpotential (284 mV at 10 mA cm-2) as well as a Tafel slope (71 mV dec-1), which outperformed the benchmark of commercial RuO2. Moreover, Ni-Co3Se4/rGO also shows high stability and long-term durability.

Nickel Nitride Particles Supported on 2D Activated Graphene-Black Phosphorus Heterostructure: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

Hydrogen is regarded as the most promising green clean energy in the 21st century. Developing the highly efficient and low-cost electrocatalysts for oxygen evolution reaction (OER) is of great concern for the hydrogen industry. In the water electrolyzed reaction, the overpotential and the kinetics are the main hurdles for OER. Therefore, an efficient and durable oxygen evolution reaction electrocatalyst is required. In this study, an activated graphene (AG)-black phosphorus (BP) nanosheets hybrid is fabricated for supporting Ni3 N particles (Ni3 N/BP-AG) in the application of OER. The Ni3 N particles are combined with the BP-AG heterostructure via facile mechanical ball milling under argon protection. The synthesized Ni3 N/BP-AG shows excellent catalytic performance toward the OER, demanding the overpotential of 233 mV for a current density of 10 mA cm-2 with a Tafel slope of 42 mV dec-1 . The Ni3 N/BP-AG catalysts also show remarkable stability with a retention rate of the current density of about 86.4% after measuring for 10 000 s in potentiostatic mode.