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Hydrogen is rapidly emerging as a clean and versatile energy carrier addressing challenges of climate change and energy sustainability. With increasing energy demand and rising application of hydrogen energy, safety while harnessing hydrogen energy is a primary concern. To enhance safety, it is critical to detect hydrogen gas during its leakage which is otherwise challenging due to its colourless, odourless and inflammable nature. Hence, there is an urgent need for the development of hydrogen sensors for rapid response, maximum absorption/desorption, high selectivity, a wide dynamic range, and a low detection limit. This review provides a comprehensive analysis of emerging nanomaterials and their composites spanning from 0D to 3D for hydrogen sensing, emphasizing the underlying mechanisms. It also deliberates on the advantages and disadvantages of a wider range of advanced materials including noble metals, metal oxide semiconductors (MOS), transition metal dichalcogenides (TMD), metal organic frameworks (MOF), Xenes and MXenes pondering over hysteresis phenomenon, commonly observed as a limitation of noble metal-based hydrogen sensors. Among these emerging materials, two dimensional nanomaterials stand out as the optimal choice for hydrogen sensing due to their large surface area, exceptional electrical properties, low operating temperatures, and ease of chemical modification. Carbon-based materials, TMDs, MOFs, and MXenes have higher gas absorption capability and excellent mechanical properties, making them suitable for low/room temperature sensing and wearable sensing platforms. The review underscores the need for reliable sensing materials and presents challenges in quantitative detection of hydrogen offering future directions for research in this field. [Display omitted] • The review features the urge to develop hydrogen sensors. • It spans a wide range of new materials used for hydrogen sensing over the last two decades. • The mechanism of hydrogen adsorption & desorption is elaborated. • The article highlights challenges & prospects of materials for hydrogen sensing. • This article is useful to researchers, scientists, and engineers working in this field. [ABSTRACT FROM AUTHOR]

To meet the escalated global energy requirements while preserving the intrinsic environmental integrity, it is highly important to develop renewable and clean energy sources as the replacement of traditional fossil fuels. Hydrogen is an appealing green energy source due to huge energy density, carbon free by products, renewable and storable nature. Water splitting is an exceedingly important technology for sustainable hydrogen generation. However, the process needs high-performance, stable, and low-cost catalyst for efficient hydrogen evolution reaction (HER). This review article aims to summarize the theoretical understanding of foundations for various H 2 development technologies along with their merits and de-merits. The essence of nanosciences for the development of nanoengineered stable and cost-effective catalysts has been comprehensively showcased by enlightening the outstanding performance of newly emergent nanocatalyst for H 2 production via water splitting. Particular consideration has been devoted to prevalent approaches that can improve the catalytic properties of the categorized nanocatalyst and provide insight towards atomic assembly related mechanism. Future consideration for catalytic enhancement is also discussed. In short, this critical review comes up with the insight essence of hybridized catalyst that are noteworthy for researchers and industrialists to sort out the best class of materials in accordance with hydrogen production techniques. [Display omitted] • Underlying mechanisms for Hydrogen production via existing water splitting techniques have been summarized. • Describes the fundamental insight of material requirements as water splitting catalyst. • Unveils the pros and cons of traditional Nanocatalyst. • Introduce features of emerging MXenes, Nano Encapsulated, Nanocurved, Janus Nanoparticles, and Single Atomic Catalyst. • The new pathways are highlighted to overcome the most encountered challenges in water splitting hydrogen generation. [ABSTRACT FROM AUTHOR]

• β -phase allotrope of Sb is synthetized by a new method based on MOCVD. • Thin Sb epitaxial nanocrystals are grown on Ge substrates by a Au-catalysed process. • Raman measurements and simulations indicate antimonene-like properties. • The new method can pave the way to large-area antimonene layers for novel devices. Synthetic two-dimensional (2D) mono-elemental crystals, namely X-enes, have recently emerged as a new frontier for atomically thin nanomaterials with on-demand properties. Among X-enes, antimonene, the β -phase allotrope of antimony, is formed by atoms arranged in buckled hexagonal rings bearing a comparatively higher environmental stability with respect to other players of this kind. However, the exploitation of monolayer or few-layer antimonene and other 2D materials in novel opto-electronic devices is still hurdled by the lack of scalable processes. Here, we demonstrated the viability of a bottom-up process for the epitaxial growth of antimonene-like nanocrystals (ANCs), based on a Metal-Organic Chemical Vapor Deposition (MOCVD) process, assisted by gold nanoparticles (Au NPs) on commensurate (1 1 1)-terminated Ge surfaces. The growth mechanism was investigated by large- and local-area microstructural analysis, revealing that the etching of germanium, catalyzed by the Au NPs, led to the ANCs growth on the exposed Ge (1 1 1) planes. As a supportive picture, ab-initio calculations rationalized this epitaxial relationship in terms of compressively strained β -phase ANCs. Our process could pave the way to the realization of large-area antimonene layers by a deposition process compatible with the current semiconductor manufacturing technology. [ABSTRACT FROM AUTHOR]