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Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the core reactions of a series of advanced modern energy and conversion technologies, such as fuel cells and metal–air cells. Among all kinds of oxygen electrocatalysts that have been reported, single‐atom catalysts (SACs) offer great development potential because of their nearly 100% atomic utilization, unsaturated coordination environment, and tunable electronic structure. In recent years, numerous SACs with enriched active centers and asymmetric coordination have been successfully constructed by regulating their coordination environment and electronic structure, which has brought the development of atomic catalysts to a new level. This paper reviews the improvement of SACs brought by atom‐level interface engineering. It starts with the introduction of advanced techniques for the characterizations of SACs. Subsequently, different design strategies that are applied to adjust the metal active center and first coordination sphere of SACs and then enhance their oxygen electrocatalysis performance are systematically illustrated. Finally, the future development of SACs toward ORR and OER is discussed and prospected. [ABSTRACT FROM AUTHOR]

• Fe-POM NP/porous and ultrathin g-C 3 N 4 nanosheet with rich N defect was fabricated. • Various emerging pollutants were almost completely removed by 45Fe- POM/CNNS-N vac. • Impact of N vacancies on ROS degradation mechanism was investigated. • Degradation pathways and products toxicity were given via theoritical calculation. Surface defect engineering has been suggested as an effective strategy to enhance photo-Fenton degradation performance. However, the underlying impact mechanism remains unknown. This study precisely constructed an efficient photo-Fenton catalyst through self-assembly of Fe-polyoxometalates nanoparticles on porous and ultrathin g-C 3 N 4 nanosheets with nitrogen vacancies (Fe-POM/CNNS-N vac). These nitrogen vacancies promoted photo-Fenton reaction rate constant for tetracycline hydrochloride (TCH) from 0.0950 to 0.1520 min−1 under visible light irradiation. Scavenging experiments and characterization results indicated that nitrogen vacancies could accelerate Fe(III)/Fe(II) conversion for OH and 1O 2 generation, and directly regulate electronic structure for O 2 − generation. The possible degradation pathways of TCH were interpreted using experimental results and frontier electron density calculations. The results indicated that holes (h+) were responsible for ring-opening and 1O 2 /OH/O 2 − contributed to demethylation, deamination, and further mineralization. This study provides novel insight for the design of highly efficient catalysts with nitrogen vacancies for the removal of emerging pollutants. [ABSTRACT FROM AUTHOR]

Low dimensional materials exhibit distinct properties compared to their bulk counterparts. A plethora of examples have been demonstrated in two-dimensional (2-D) materials, including graphene and transition metal dichalcogenides (TMDCs). These novel and intriguing properties at the nano-, molecular- and even monatomic scales have triggered tremendous interest and research, from fundamental studies to practical applications and even device fabrication. The unique behaviors of 2-D materials result from the special structure–property relationships that exist between surface topographical variations and mechanical responses, electronic structures, optical characteristics, and electrochemical properties. These relationships are generally convoluted and sensitive to ambient and external perturbations. Characterizing these systems thus requires techniques capable of providing multidimensional information under controlled environments, such as atomic force microscopy (AFM). Today, AFM plays a key role in exploring the basic principles underlying the functionality of 2-D materials. In this tutorial review, we provide a brief introduction to some of the unique properties of 2-D materials, followed by a summary of the basic principles of AFM and the various AFM modes most appropriate for studying these systems. Following that, we will focus on five important properties of 2-D materials and their characterization in more detail, including recent literature examples. These properties include nanomechanics, nanoelectromechanics, nanoelectrics, nanospectroscopy, and nanoelectrochemistry. [ABSTRACT FROM AUTHOR]