Single-atom catalysts (SACs) have emerged as a hot research topic in recently years, and have been intensively investigated for energy storage and conversion applications. Significant advances in the synthesis of SACs have been achieved through enormous efforts in this area, however, their application is hindered by the low active site loading and poor long-term stability. In contrast with other methods, atomization, in which the SACs are synthesized from transformation of the nanoparticles to atomic sites, is a very attractive and innovative top-down approach to achieve high-density supported active sites with outstanding stability. However, limited attention has been paid to this area, despite the significant advances achieved in the past two years. In this short review, we discuss in detail the latest advances in atomization approaches for the synthesis of SACs and highlight the associated advantages and opportunities.

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Hollow mesoporous silica (HMS) has attracted significant attention for fuel cell applications. The mesopores in the shell can accelerate proton transport and the void in the center of the particle is advantageous for proton storage. However, the conventional methods for HMS fabrication are complicated, which is not conducive to scaling up the fabrication of HMS. In this work, a new, simple strategy to synthesize HMS has been developed via OH− ion exchange-induced etching of mesoporous silica (mSiO2). The mSiO2 immersed in an alkaline Na2CO3 solution led to an exchange of the Br− ions in the surfactant with the OH− ions in the solution, resulting in a high concentration of OH− ions in the mesoporous channels of mSiO2 close to the core, and a low concentration of OH− ions close to the surface. This demonstrated that the etching of the core of mSiO2 was induced, which extended from the core to the surface of the nanoparticles. Furthermore, the success of the ion exchange-induced etching process was demonstrated by the gradient distribution of the Na+ ion in mesoporous silica microspheres through microscopy. In addition, the proton conductivity of the phosphoric acid-impregnated HMS membrane at 180°C under anhydrous conditions was found to be 0.025 S.cm−1. These results demonstrate the simplicity of the ion exchange-induced etching strategy for the fabrication of HMS microspheres and its promising application in high temperature proton exchange membrane fuel cells.

Coccotorus beijingensis Lin et Li, 1990 belongs to Coleoptera, Curculionidae, Curculioninae, Anthonomini. It is a herbivorous insect that damages Celtis bungeana Blume (Ulmaceae) by affecting branch growth. The mitochondrial genome of C. beijingensis was sequenced and annotated to better identify C. beijingensis and related species. The total length of the C. beijingensis mitochondrial genome was 17,071 bp, contained 37 typical genes (13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes) and two control regions (total length: 2,292 bp). Mitochondrial genome composition, nucleotide composition and codon usage are similar to those of other sequenced Curculionidae mitogenomes. All protein-coding genes initiated with ATN and TTG codons and ended with TAA, TAG or incomplete stop codons (TA, T). In addition, analyses of pairwise genetic distances between individual PCGs in Curculionidae species showed that ATP8 was the least conserved gene, while COI was the most conserved. Twenty-one transfer RNAs had typical cloverleaf structures, while trnS1 lacked dihydrouridine (DHU) arms. ML and BI analyses, based on 13 PCGs and two rRNAs from ten species of Curculionidae, strongly support the relationships between C. beijingensis and species of the genus Anthonomus: ((An. eugenii+ An. rubi) + C. beijingensis + (An. pomorum+ An. rectirostris)) (BS = 100; PP = 1). Our phylogenetic analyses could mean that the genus Coccotorus should be sunk under Anthonomus, but more taxon sampling is needed to verify this result.