The overall water splitting efficiency is mainly restricted by the slowkinetics of oxygen evolution. Therefore,it is essential to develop active oxygen evolution catalysts.Inthis context, we designed and synthesized atungsten oxide catalyst with oxygen vacancies for photocatalytic oxygen evolution, which exhibited ah igher oxygen evolution rate of 683 mmol h À1 g À1 than that of pure WO 3 (159 mmol h À1 g À1). Subsequent studies through transient absorption spectroscopy found that the oxygen vacancies can produce electron trapping states to inhibit the direct recombination of photogenerated carriers.Additionally,aPt cocatalyst can promote electron trap states to participate in the reaction to improve the photocatalytic performance further.T his work uses femtosecond transient absorption spectroscopytoexplain the photocatalytic oxygen evolution mechanism of inorganic materials and provides new insights into the design of high-efficiency watersplitting catalysts.

Undesired photoelectronic dormancy through active species decay is adverse to photoactivity enhancement. An insufficient extrinsic driving force leads to ultrafast deep charge trapping and photoactive species depopulation in carbon nitride (g-C 3 N 4 ). Excitation of shallow trapping in g-C 3 N 4 with longlived excited states opens up the possibility of pursuing high-efficiency photocatalysis. Herein, a near-field-assisted model is constructed consisting of an In 2 O 3 -cube/g-C 3 N 4 heterojunction associated with ultrafast photodynamic coupling. This In 2 O 3 -cube-induced near-field assistance system provides catalytic "hot areas", efficiently enhances the lifetimes of excited states and shallow trapping in g-C 3 N 4 and this favors an increased active species density. Optical simulations combined with time-resolved transient absorption spectroscopy shows there is a built-in charge transfer and the active species lifetimes are longer in the In 2 O 3 -cube/g-C 3 N 4 hybrid. Besides these properties, the estimated overpotential and interfacial kinetics of the In 2 O 3 -cube/g-C 3 N 4 hybrid co-promotes the liquid phase reaction and also helps in boosting the photocatalytic performance. The photocatalytic results exhibit a tremendous improvement (34-fold) for visible-light-driven hydrogen production. Near-fieldassisted long-lived active species and the influences of trap states is a novel finding for enhancing (g-C 3 N 4 )-based photocatalytic performance.

Defects have been observed in graphene and are expected to play a key role in its optical, electronic, and magnetic properties. However, because most of the studies focused on the structural characterization, the implications of topological defects on the physicochemical properties of graphene remain poorly understood. Here, we demonstrate a bottom-up synthesis of three novel nanographenes (1−3) with well-defined defects in which seven-five-seven (7− 5−7)-membered rings were introduced to their sp 2 carbon frameworks. From the X-ray crystallographic analysis, compound 1 adopts a nearly planar structure. Compound 2, with an additional five-membered ring compared to 1, possesses a slightly saddle-shaped geometry. Compound 3, which can be regarded as the "head-to-head" fusion of 1 with two bonds, features two saddles connected together. The resultant defective nanographenes 1−3 were well-investigated by UV−vis absorption, cyclic voltammetry, and time-resolved absorption spectra and further corroborated by density functional theory (DFT) calculations. Detailed experimental and theoretical investigations elucidate that these three nanographenes 1−3 exhibit an anti-aromatic character in their ground states and display a high stability under ambient conditions, which contrast with the reported unstable biradicaloid nanographenes that contain heptagons. Our work reported herein offers insights into the understanding of structure-related properties and enables the control of the electronic structures of expanded nanographenes with atomically precise defects.Article pubs.acs.org/JACS

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