Finally, the outlooks in modulating the SSCs and developing operando XAS/SAXS for SSCs are highlighted. Furthermore, the reversible transformation of single‐atom catalysts (SACs) to subnanoclusters/nanoparticles and the application of in situ XAS/SAXS in subnanoclusters are discussed. The recent advances in applying in situ XAS/SAXS to SSCs are thoroughly summarized in this review, including the atomic structure and oxidation state variations under open circuit and realistic reaction conditions.

Unfortunately, there is no detailed summary of XAS/SAXS characterization results of SSCs. In situ X‐ray absorption spectroscopy/small‐angle X‐ray scattering (XAS/SAXS) is promising and widely used for monitoring electronic structure, atomic configuration, and size changes of SSCs during real‐time working conditions. Exploring the active sites of catalysts through in situ characterization techniques plays a critical role in studying reaction mechanism and guiding the design of optimum catalysts. However, SSCs are susceptible to undergo restructuring during the reactions. Single‐atom and subnanocluster catalysts (SSCs) represent a highly promising class of low‐cost materials with high catalytic activity and high atom‐utilization efficiency. This new plastic to low-aromatic naphtha technology highlights the feasibility of upcycling waste plastics into virgin plastic products. Furthermore, the pure and real-world plastic mixture can also be used to produce high quality naphtha, with a C5-C12 paraffin selectivity of 60.39 % peak area and 57.16 % peak area, respectively. This tandem catalysis system was also applicable to catalytic reforming of various waste polyolefins including HDPE, low density polyethylene (LDPE), and polypropylene (PP), producing high quality naphtha with a C5-C12 paraffin selectivity of 50–71 % peak area. This catalyst shows a much higher activity than pure catalysts or SBA-15 catalysts that were modified with other metals. Zn/SBA-15 was found to be an effective heterogeneous catalyst for cracking high density polyethylene (HDPE) pyrolytic wax into short chain olefins. This study presents a novel catalytic conversion of waste polyolefinic plastics to low aromatic naphtha for new plastic manufacturing by a tandem catalysis process.

The global waste plastic crisis, caused by overconsumption of single-use plastics, is threatening ecological systems and public health, worldwide. Combining in situ/operando small‐angle X‐ray scattering/X‐ray absorption spectroscopy to study nanomaterials’ nucleation/growth mechanism during the synthesis process and the changes of the nanomaterials under the working state is helpful for the development of nanomaterials. Nanostructured materials present distinct intrinsic properties from their bulk counterparts. In addition, the application of in situ/operando XAS and SAXS in preparing nanomaterials and studying changes of working nanomaterials are summarized. This review gives a brief introduction to in situ/operando SAXS/XAS cells. A combination of in situ/operando XAS and SAXS provides high temporal and spatial resolution to monitor the evolution of nanomaterials. As two indispensable methods, X‐ray absorption spectroscopy (XAS) provides nanomaterials’ electronic structure and coordination environment, while small‐angle X‐ray scattering (SAXS) offers structural properties and morphology information. However, nanomaterials’ nucleation/growth mechanism during the synthesis process and the changes of the nanomaterials in the working state are still not thoroughly studied. Nanostructured materials with high surface area and low coordinated atoms present distinct intrinsic properties from their bulk counterparts.

Cracking of dodecane to make ethene