RESUMEN
As a typical perovskite-type crystal, polyhedral strontium titanate (SrTiO3 ) has shown anisotropic charge transport behavior in recent studies, however, the carrier transportation and transition of which has not been explained very clearly. This work present the existence of Sr and O divacancies in the novel rhombicuboctahedron SrTiO3 micro/nano particles (Sr1- x TiO3- x /TiO2- x ) with exposing (100), (110) and (111) facets and the diameter of 300-700 nm synthesized via hydrothermal synthesis, and also summarizes the dissociation mechanism of self-trapped excitons (STEs) caused by the divacancy and facet effect. In addition, most importantly, the metastable STEs with ultra-low binding energy (Eb < 3 meV) under illumination are discovered. Combining the model of S-scheme heterojunction, a conversion mechanism of photoinduced carriers is proposed. The photocatalytic reaction of Co2+ is used as the probe reaction, and the unique Sr1- x TiO3- x /TiO2- x possesses a high photooxidation efficiency of Co2+ , by which 70.3% of Co2+ is oxidized to Co3+ (CoOOH) in 5 min. This finding may provide a guideline for an optimal design of the photocatalytic materials for the recovery and extraction of metal ions based on SrTiO3 .
RESUMEN
More and more two-dimensional materials, such as graphene, are used in water separation membrane synthesis. Among the main influencing factors, surface properties and the interface structure of multilayers are the two crucial factors to the membrane separation performance. In the present paper, a silanol ((SiO3)x) and graphene oxide nanosheet composite (GO-(SiO3)x) was used to synthesize a skin like forward osmosis (FO) membrane for desalination by a surface layer-by-layer self-assembly method. We tested the separation performance of the FO membranes using DI water and 1.5 M NaCl aqueous solutions as feed and draw solutions, respectively. The results show that the molecular size and particle morphology of (SiO3)x grafted onto GO nanosheets play main roles in the water flux of the composite membrane. Based on this property and the self-assembly method, we can control the number of composite layers and the space between the GO nanosheets. Simultaneously, we have introduced a new concept: dilutive "skin layer concentration polarization (SLCP)" and the concentrative external concentration polarization (ECP) effect at the membrane surface are considered. The FO membrane synthesized in the current study exhibits a high level of water flux (above 30 L·m-2·h-1), and the salt retention capacity of the membranes increases as the number of composite layers increases. Thus, in this article, we find a way to create suitable water channels for separation of salt/water in a FO process by controlling the GO-(SiO3)x content and size.
RESUMEN
Crystal facet regulation is an effective method for preparing SrTiO3 or other perovskite semiconductor materials with high photochemical catalysis performance. In general, the edge-truncated cube of SrTiO3 micro-nano particles has been widely reported because of the multiple crystal facets exposed at the same time. However, the effect of the (110) facet and the interaction between the (100) and (110) facets on the properties of photo-induced carriers is still not very clear. In this article, we have designed and prepared two edge-truncated cube SrTiO3-a small and large area proportion of the (110) facet, respectively. In addition to the morphological and structural characterization, high-resolution XPS and femtosecond multiphoton transient absorption (fs-TA) spectroscopy were used to detect the atomic vacancy and were applied to confirm the state of carrier transition. The results showed that the larger (110) facet led to two influences-more Sr vacancies and more self-trapping excitons (STEs) with an ultra-low binding energy (Eb = 2.13 meV), about 1.17 meV lower than that of the sample with the smaller (110) facet. In particular, the larger (110) facet also caused a much higher photooxidation performance for Co2+ to Co3+. This study not only enriches the arsenal of SrTiO3 materials but also sheds new insights into the understanding of the synergistic effect essence of the (100) and (110) facets, which could promote the development of new perovskite photocatalytic materials, particularly in the recovery of heavy metals.