Dyes are used in various industries as coloring agents. The discharge of dyes, specifically synthetic dyes, in wastewater represents a serious environmental problem and causes public health concerns. The implementation of regulations for wastewater discharge has forced research towards either the development of new processes or the improvement of available techniques to attain efficient degradation of dyes. Catalytic oxidation is one of the advanced oxidation processes (AOPs), based on the active radicals produced during the reaction in the presence of a catalyst. This paper reviews the problems of dyes and hydroxyl radical-based oxidation processes, including Fenton’s process, non-iron metal catalysts, and the application of thin metal catalyst-coated tubular reactors in detail. In addition, the sulfate radical-based catalytic oxidation technique has also been described. This study also includes the effects of various operating parameters such as pH, temperature, the concentration of the oxidant, the initial concentration of dyes, and reaction time on the catalytic decomposition of dyes. Moreover, this paper analyzes the recent studies on catalytic oxidation processes. From the present study, it can be concluded that catalytic oxidation processes are very active and environmentally friendly methods for dye removal.

A general rise in environmental and anthropogenically induced greenhouse gas emissions has resulted from worldwide population growth and a growing appetite for clean energy, industrial outputs, and consumer utilization. Furthermore, well-established, advanced, and emerging countries are seeking fossil fuel and petroleum resources to support their aviation, electric utilities, industrial sectors, and consumer processing essentials. There is an increasing tendency to overcome these challenging concerns and achieve the Paris Agreement’s priorities as emerging technological advances in clean energy technologies progress. Hydrogen is expected to be implemented in various production applications as a fundamental fuel in future energy carrier materials development and manufacturing processes. This paper summarizes recent developments and hydrogen technologies in fuel refining, hydrocarbon processing, materials manufacturing, pharmaceuticals, aircraft construction, electronics, and other hydrogen applications. It also highlights the existing industrialization scenario and describes prospective innovations, including theoretical scientific advancements, green raw materials production, potential exploration, and renewable resource integration. Moreover, this article further discusses some socioeconomic implications of hydrogen as a green resource.

Bimetallic phosphide (Ni_xFe_1−x)₂P hollow nanocubes were prepared from PBAs as highly active and stable OER electrocatalysts.

Heterogeneous catalytic hydrogenation reactions are of great importance to the petrochemical industry and fine chemical synthesis. Herein, we present the first example of gadolinium hydroxide (Gd(OH)₃) nanorods as a support for loading ultra-small Pd nanoparticles for hydrogenation reactions. Gd(OH)₃ possesses a large number of hydroxyl groups on the surface, which act as an ideal support for good dispersion of Pd nanoparticles. Gd(OH)₃ nanorods are prepared by hydrothermal treatment, and Pd/Gd(OH)₃ catalyst with a low loading of 0.95 wt% Pd is obtained by photochemical deposition. The catalytic hydrogenation of p-nitrophenol (4-NP) to p-aminophenol (4-AP) and styrene to ethylbenzene is performed as a model reaction. The obtained Pd/Gd(OH)₃ catalyst displays excellent activity as compared to other reported heterogeneous catalysts. The rate constant of 4-NP reduction is measured to be 0.047 s⁻¹ and the Pd/Gd(OH)₃ nanocatalyst shows no marked loss of activity even after 10 consecutive cycles. Additionally, the hydrogenation of styrene to ethylbenzene over Pd/Gd(OH)₃ nanorods exhibits a turnover frequency (TOF) as high as 6159 h⁻¹ with 100% selectivity. Moreover, the catalyst can be recovered by centrifugation and recycled for up to 5 consecutive cycles without obvious loss of activity. Our results indicate that Gd(OH)₃ nanorods act as a promoter to enhance the catalytic activity by providing a synergistic effect from the strong metal support interaction and the large surface area for high dispersion of small sized Pd nanoparticles enriched with hydroxyl groups on the surface. The high performance of Pd/Gd(OH)₃ in heterogeneous catalysis offers a new, efficient and facile strategy to explore other metal hydroxides or oxides as supports for organic transformations.