Platinum-nanoparticle-based catalysts are widely used in many important chemical processes and automobile industries. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their use efficiency, however, very challenging. Here we report a practical synthesis for isolated single Pt atoms anchored to graphene nanosheet using the atomic layer deposition (ALD) technique. ALD offers the capability of precise control of catalyst size span from single atom, subnanometer cluster to nanoparticle. The single-atom catalysts exhibit significantly improved catalytic activity (up to 10 times) over that of the state-of-the-art commercial Pt/C catalyst. X-ray absorption fine structure (XAFS) analyses reveal that the low-coordination and partially unoccupied densities of states of 5d orbital of Pt atoms are responsible for the excellent performance. This work is anticipated to form the basis for the exploration of a next generation of highly efficient single-atom catalysts for various applications.

It has been a strong desire for researchers to control material growth at the molecular and atomic levels. Molecular and atomic layer deposition (MLD and ALD) are two such techniques. In comparison to a huge amount of studies invested on ALD, the research on MLD is still relatively limited due to the difficulty in finding suitable coupling precursors, but the recently successful applications of MLD are very encouraging in many areas such as surface engineering, new energies, and catalysis. In order to further stimulate more research enthusiasm and educate beginners, we contribute this thorough survey on the progress of MLD. This review is a comprehensive account of MLD processes for organic and organic–inorganic materials, covering precursors, surface chemistry, growth characteristics, film properties, and promising applications. The work provides a complete summary of over 80 MLD processes for growing over 20 types of pure polymeric and metal-based hybrid polymeric materials. Given their similarities in mechanisms, we made a comparative description between ALD and MLD, and discussed the uncountable possibilities to combine both ALD and MLD for advanced materials with desirable properties. To feature and highlight the significance of MLD, this review specially gives some detailed discussions on MLD's applications in several important areas, including novel nanostructured materials, surface engineering, new energies (i.e., batteries, supercapacitors, solar cells, and water splitting), catalysis, and rewritable data storage. With this work, we expect to boost research interest and attempts at advanced materials using MLD as well as ALD.

This review describes recent advances in two-dimensional MoS ₂ nanosheets and their composite materials for understanding their high-electrocatalytic performance in HER and ORR.