Photocatalysts with oxygen vacancies (OVs) have exhibited exciting activity in N2 photofixation due to their superiority in capture and activation of N2. However, the surface OVs are easily oxidized by seizing the oxygen atoms from water or oxygen during the catalytic reaction. Here, it is reported that the grain boundaries (GBs) in nanoporous WO3 induce plenty of operando OVs under light irradiation to significantly boost catalytic activity toward N2 photofixation. Impressively, nanoporous WO3 with abundant GBs (WO3‐600) exhibit an ammonia production rate of 230 µmol gcat.−1 h−1 without any sacrificial agents at room temperature, 17 times higher than that for WO3 nanoparticles without GBs. Moreover, WO3‐600 also manifests remarkable stability by maintaining nearly ≈100% catalytic activity after ten successive reaction rounds. Further mechanistic studies reveal that both OVs and GBs regulate the band structures of WO3 nanocrystals, as well as favor the delivery of photogenerated electrons to adsorbed N2 by enhancing W–O covalency. More importantly, plenty of operando OVs induced by GBs generate during catalytic reaction, directly contributing to the excellent catalytic performance for WO3‐600. This work opens a novel avenue to developing efficient photocatalysts by construction of operando OVs.
Reduction of soluble hexavalent uranium (U(VI)) to sparingly soluble tetravalent uranium (U(IV)) with semiconductor photocatalysts is recognized as a novel, green, and simple U‐extraction method. Furthermore, effective charge separation and utilization are critical factors to achieve high‐efficiency U(VI) photoreduction. Herein, a UiO‐66‐based heterostructured photocatalyst (MnOx/UiO‐66/Ti3C2Tx) with spatially separated dual cocatalysts (MnOx nanoparticles and Ti3C2Tx MXene nanosheets) is successfully developed for efficient U(VI) photoreduction without sacrificial agents. As co‐catalysts, MnOx nanoparticles favor the trapping of holes, while Ti3C2Tx MXene nanosheets tend to collect electrons. Consequently, the photogenerated holes and electrons flow into and out of the photocatalyst, respectively, achieving efficient charge separation required by MnOx/UiO‐66/Ti3C2Tx to remove U(VI). Impressively, the U(VI) removal ratio via MnOx/UiO‐66/Ti3C2Tx reaches to 98.4% in the U(VI) solution after 60 min, with a photoreaction rate constant of 0.0948 min−1. Moreover, MnOx/UiO‐66/Ti3C2Tx exhibits brilliant U(VI) extraction capacity in various U(VI) wastewater and U(VI)‐spiked real seawater. Further mechanistic studies indicates that the photogenerated electrons are transferred from the conduction band of UiO‐66 to Ti3C2Tx MXene to reduce U(VI) and generate ·O2–, further leading to a stable crystal phase of (UO2)O2·2H2O. Furthermore, the photogenerated holes are extracted by MnOx nanoparticles in MnOx/UiO‐66/Ti3C2Tx to oxidize water.
Tough and biocompatible nanocomposite films: A new type of bioinspired ultrastrong, highly biocompatible, and bioactive konjac glucomannan (KGM)/graphene oxide (GO) nanocomposite film is fabricated on a large scale by a simple solution-casting method. Such KGM-GO composite films exhibit much enhanced mechanical properties under the strong hydrogen-bonding interactions, showing great potential in the fields of tissue engineering and food package.
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