Exploration of electrocatalysts for clean and sustainable hydrogen generation from water splitting has received huge attention due to the depletion of fossil fuels and environmental pollution. Although platinum (Pt) is the most efficient catalyst for the hydrogen evolution reaction (HER), it has limitations for widespread applications due to its towering cost, scarcity and instability. Various catalysts such as precious/non-precious metal and metal-free catalysts have been developed for a viable HER process. Among them, ruthenium (Ru) based catalysts, which possess appropriate hydrogen bonding energy and reasonable price, have demonstrated strong potential as an alternative to Pt for the HER. In this review article, we summarize recently developed Ru-based electrocatalysts with superior HER performance, i.e., Ru on carbon supports, Ru phosphide based catalysts, and Ru coupled with transition metals. Finally, we discuss the challenges and perspectives of Ru-based catalysts in the HER research field.

Although polymers are very important and vastly used materials, their physical properties are limited. Therefore, they are reinforced with fillers to relieve diverse restrictions and expand their application areas. The exceptional properties of graphene make it an interesting material with huge potential for application in various industries and devices. The interfacial interaction between graphene and the polymer matrix improved the uniform graphene dispersion in the polymer matrix, enhancing the general nanocomposite performance. Therefore, graphene functionalization is essential to enhance the interfacial interaction, maintain excellent properties, and obstruct graphene agglomeration. Many studies have reported that graphene/polymer nanocomposites have exceptional properties that enable diverse applications. The use of graphene/polymer nanocomposites is expected to increase sustainably and to transform from a basic to an advanced material to offer optimum solutions to industry and consumers.

Hyperbranched macromolecules (HMs, also called hyperbranched polymers) are highly branched three-dimensional (3D) structures in which all bonds converge to a focal point or core, and which have a multiplicity of reactive chain-ends. This review summarizes major types of synthetic strategies exploited to produce HMs, including the step-growth polycondensation, the self-condensing vinyl polymerization and ring opening polymerization. Compared to linear analogues, the globular and dendritic architectures of HMs endow new characteristics, such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility. After discussing the general concepts, synthesis, and properties, various applications of HMs are also covered. HMs continue being materials for topical interest, and thus this review offers both concise summary for those new to the topic and for those with more experience in the field of HMs.