Electrocatalytic water splitting has appeared to be a sustainable green technology for hydrogen and oxygen production, and noble metal-based electrocatalysts, like Pt for hydrogen evolution reaction (HER) and RuO₂/IrO₂ for oxygen evolution reaction (OER) have been proved to be state-of-the-art in water electrolyzers. However, high cost and scarcity of noble metals hinder large-scale applications of these electrocatalysts in practical commercial water electrolyzers. As an alternative, transition metal based electrocatalysts have attracted great attention because of the exciting catalytic performance, cost-effectiveness and abundant availability. However, their long-term stability in water splitting devices is unsatisfactory because of agglomeration and dissolution in the harsh operating environment. A possible solution to this issue is encapsulating transition metal (TM) based materials in stable and highly conductive carbon nanomaterials (CNMs) to make a hybrid of TM/CNMs, and the performance of TM/CNMs could be further enhanced by heteroatom (N-, B-, and dual N,B-) doping to carbon network in CNMs to break the carbon electroneutrality due to the different electronegativity, modulate the electronic structure to facilitate the adsorption of reaction intermediates, and promotion of efficient electron transfer to enhance the number of catalytically active sites for water splitting operation. In this review article, the recent progress of TM-based materials hybridizing with CNMs, N-CNMs, B-CNMs, and N,B-CNMs as electrocatalysts towards HER, OER as well as overall water splitting have been summarized, and the challenges and future prospects are also discussed.

The determined need for a sustainable energy economy has evoked the increasing interest of researchers concerning the discovery of smart material designs of layered double hydroxide (LDH) nanocomposites for energy-based applications. This paper presents a novel method for the direct growth of brominated graphene and layered triple hydroxide (LTH) on 3D nickel foam (NF) as a supercapacitor electrode by a facile one-step in situ crystallization hydrothermal method. Subsequently, the as-synthesized NCA-L@BG-NF hybrids were characterized by TEM, SEM, HRTEM, XRD, FT-IR, RAMAN, XPS, and EDS. Moreover, the electrochemical performance disclosed that by fine-tuning the Ni/Co/Al mole ratios, it was possible to obtain optimized ratio of NCA-L@BG-NF-3 to display the maximum specific capacity of 1998 C g⁻¹ at 6 A g⁻¹, excellent rate capability of 75.3% at 20 A g⁻¹, and excellent cyclic stability of ∼91% capacitance retention after 2000 cycles at 20 A g⁻¹ with 100% coulombic efficiency. Furthermore, the greater electrochemical performance of LTH was achieved and synergistically strengthened with a high surface area provided by the conducting brominated graphene oxide framework directly grown on a 3D porous NF to form a binder-free electrode, which could improve the electrochemical performance in terms of charge transport and storage. Accordingly, these remarkable properties show that NCA-L@BG-NF-3 may be considered as a promising candidate for high-performance supercapacitor applications.

The requisite to obtain reduced graphene oxide as an individual sheet and to maintain it in the reduced form introduces a new way of manipulative nanocomposite systems (e.g., semiconductor or metal nanoparticle and graphene composite). Herein, we developed a simple suitable UV-.assisted photocatalytic reduction method to prepare the most viable nanocomposite ZnO/RGO. Graphene oxide undergoes reduction reaction in ethanol- water system as it accepts electrons from UV irradiated semiconductor (ZnO), and subsequently characterized using different standard techniques. The presence of graphene in the composites were confirmed by X-ray diffraction (XRD), Raman, FTIR, SEM, TEM, and X-ray photoelectron spectroscopy (XPS) analysis. The highly efficient ZnO/RGO nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methylene blue, with a maximum removal rate of (∼80%) as compared with pure ZnO nanoparticles (∼68%). This effective increase in degradation were caused by the prevention of electron–hole pair recombination in ZnO with the introduction of RGO. These findings suggest that the synthesized ZnO/RGO nanocomposite via photocatalytic approach not only offers UV-assisted reduction technique, but also open up a new way to obtain photoactive graphene-semiconductors, which could be effectively used in various application.