As a result of the powerful quantum confined space effects and multiple modes of very tiny atomic sizes, metal nanoclusters (NCs) that consist of thiolate-protected noble metals, such as silver (Ag) and gold (Au) have core sizes less than 3 nm, have emerged as a class of "metallic molecules" with a wide range of molecule-like optical, magnetic, and electronic properties. To investigate well-defined nanocatalysts, especially ligand-passivated metal nanoclusters, great strides have been achieved in the efficient synthesis of atomically precise nanoparticles. Methods of synthesis such as bottom-up growth, top-down approach, ligand engineering, and the interconversion system are covered in this overview. Such clearly defined metal nanoclusters have demonstrated considerable promise in catalysis research and have evolved into a distinct class of model catalysts. Focusing on the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER), this article attempts to outline current developments in nanoclusters of molecular metal employed in electrocatalytic reactions. The paper also highlights the connection between the catalytic mechanism's structure and performance as well as examines the potential effects of metal clusters' sizes, metal core structures, charges, ligands, and metal-ligand binding patterns on their electrocatalytic activity. Future research opportunities and challenges are also proposed.

Supported nano-silver (nano-Ag) catalysts have been widely used in heterogeneous catalysis. However, their poor thermal stability restricts their practical application. In order to solve this issue, we report a novel supported nano-Ag catalyst by employing the strong metal–support interactions (SMSIs) between the Ag nanoparticles (NPs) and hydroxyapatite (HAP). The home-made HAP was prepared via a facile hydrothermal or co-precipitation method, which can effectively anchor small size Ag NPs prepared by an impregnation method. Taking advantage of the unique confinement effect with different morphology HAP and the protective effect of hydroxyl groups on the HAP surface, highly dispersed Ag NPs were obtained. These Ag/HAP catalysts were characterized by XRD, N₂ physical adsorption, SEM, TEM and XPS. It was found that the particle size of Ag NPs was strongly related to the morphology and structure of the HAP supports, and it significantly affects the CO oxidation performance. The nano-Ag catalyst with a lamellar nanosheet structure HAP has the highest content of Ag⁰, and 100% CO conversion can be achieved at 160 °C. The Ag NPs loaded on HAP nanosheets with a large specific surface area showing excellent CO oxidation activity demonstrating that the strategy may open a new way to design and develop highly dispersed nano-Ag catalysts for heterogeneous catalysis.

In this study, we synthesized sodium dodecyl sulfate modified hydroxyapatite (SDS-HAP) to enhance the removal efficiency of rhodamine B (RhB) dye. The SDS-HAP prepared using the sol–gel method exhibited a significantly higher adsorption capacity compared to pristine HAP. Various characterization techniques, including X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), were utilized to systematically investigate the morphological and structural changes. Batch experiments were conducted to evaluate the influence of RhB concentration, pH value, temperature, dosage, and contact time on the adsorption performance. Results indicated that the addition of SDS increased the specific surface area from 72.8 to 136.8 m² g⁻¹. The equilibrium adsorption capacity of SDS-HAP for RhB was approximately 3.3 times greater than that of pure HAP. Kinetic studies revealed rapid equilibrium following the pseudo-second-order model (R² = 0.9999). The Freundlich isotherm model best described the experimental data, with a maximum adsorption capacity of 44.1 mg g⁻¹. Thermodynamic analysis confirmed that the adsorption process was spontaneous, endothermic, and driven by hydrogen bonding and electrostatic interactions between the dye molecules, PO₄ ³⁻, Ca²⁺ and OH⁻.

Ultrasmall metal nanoclusters are revolutionary developments in sustainable chemical synthesis and electrochemical energy conversion. Critical activities including the oxygen evolution reaction, oxygen reduction reaction, and the electrosynthesis of urea via nitrate and carbon dioxide co-reduction are addressed by their distinctive atomic-scale designs, which provide remarkable catalytic activity, selectivity, and stability. Recent advancements in the design and synthesis of these materials are compiled in this study, which highlights how their electrical characteristics and structural tunability enable high-efficiency energy conversions. Important issues are examined critically, along with new approaches to overcome them, such as operational stability, scalable manufacturing, and the financial constraints of noble metals. Innovative strategies including machine learning-guided catalyst tuning, hybrid material systems, and synergistic effects are given special attention. This analysis offers a road map for overcoming these sophisticated catalysts' present drawbacks by combining computational modeling with experimental observations. Their potential to transform sustainable energy technologies and promote the creation of environmentally benign, scalable solutions for chemical and energy applications is highlighted in the debate. The importance of single-atom catalysts and ultrasmall nanoclusters in meeting the urgent worldwide need for sustainable energy solutions is highlighted by this study.