A minireview on the synthesis of single atom catalysts.

Single atom catalysis is a prosperous and rapidly growing research field, owing to the remarkable advantages of single atom catalysts (SACs), such as maximized atom utilization efficiency, tailorable catalytic activities as well as supremely high catalytic selectivity. Synthesis approaches play crucial roles in determining the properties and performance of SACs. Over the past few years, versatile methods have been adopted to synthesize SACs. Herein, we give a thorough and up-to-date review on the progress of approaches for the synthesis of SACs, outline the general principles and list the advantages and disadvantages of each synthesis approach, with the aim to give the readers a clear picture and inspire more studies to exploit novel approaches to synthesize SACs effectively.

Effect of preparation methods of CeO2 on the properties and performance of Ni/CeO2 in CO2 reforming of CH4.

CO2 reforming of CH4 (CRM) is not only beneficial to environmental protection, but also valuable for industrial application. Different CeO2 supports were prepared to investigate the matching between Ni and CeO2 over Ni/CeO2 and its effect on CRM. The physicochemical properties of Ni/CeO2-C (commercial CeO2), Ni/CeO2-H (hydrothermal method) as well as Ni/CeO2-P (precipitation method) were characterized by XRD, N2 adsorption at - 196 °C, TEM, SEM-EDS, H2-TPR, NH3-TPD and XPS. Ni0 with good dispersion and CeO2 with more oxygen vacancies were obtained on Ni/CeO2-H, proving the influence on Ni/CeO2 catalysts caused by the preparation methods of CeO2. The initial conversion of both CO2 and CH4 of Ni/CeO2-H was more than five times that of Ni/CeO2-P and Ni/CeO2-C. The better matching between Ni and CeO2 on Ni/CeO2-H was the reason for its best catalytic performance in comparison with the Ni/CeO2-C and Ni/CeO2-P samples.

Techniques for the characterization of single atom catalysts.

Single atom catalysts (SACs) are a hot research area recently. Over most of the SACs, the singly dispersed atoms are the active sites, which contribute to the catalytic activities significantly compared with a catalyst with continuously packed active sites. It is essential to determine whether SACs have been successfully synthesized. Several techniques have been applied for the characterization of the dispersion states of the active sites over SACs, such as Energy Dispersive X-ray spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS), etc. In this review, the techniques for the identification of the singly dispersed sites over SACs are introduced, the advantages and limitations of each technique are pointed out, and the future research directions have been discussed. It is hoped that this review will be helpful for a more comprehensive understanding of the characterization and detection methods involved in SACs, and stimulate and promote the further development of this emerging research field.