Artificial photosynthesis from CO reduction is severely hampered by the kinetically challenging multi-electron reaction process. Oxygen vacancies (Vo) with abundant localized electrons have great potential to overcome this limitation. However, surface Vo usually have low concentrations and are easily oxidized, causing them to lose their activities. For practical application of CO photoreduction, fabricating and enhancing the stability of Vo on semiconductors is indispensable. Here we report the first synthesis of ultrathin WO·0.33HO nanotubes with a large amount of exposed surface Vo sites, which can realize excellent and stable CO photoreduction to CHCOOH in pure water under solar light. The selectivity for acetum generation is up to 85%, with an average productivity of about 9.4 μmol g h. More importantly, Vo in the catalyst are sustainable, and their concentration was not decreased even after 60 h of reaction. Quantum chemical calculations and in situ DRIFT studies revealed that the main reaction pathway might be CO → COOH → (COOH) → CHCOOH.

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High-pressure rocksalt ZnO with a band gap of 1.8 eV, which can absorb visible light.

layered MnO 2 materials, composed of exotic electronic properties and accessible active sites with alkali metal ions, provide a comprehensive platform for developing catalysts with chemical modification. Significantly, K + -contained layered MnO 2 catalysts have been verified as strong candidates toward catalytic oxidation of formaldehyde (HCHO). Unveiling the effects of alkali metal ions on active sites is critical to understand the interaction between reactants and active centers. Through a combination of analytical tools with periodic computational density functional theory modeling, the surface structures and the exposing specific defects of alkali metal ions affiliated to oxygen vacancies (Vo) are figured out by comparing three typical alkali metal ionintercalated (Na + , K + , and Cs + ) layered MnO 2 materials. These materials have been synthesized via a molten salt method, with high yield, large lateral size, and nanometer thickness in a few moments. We demonstrate that the alkali metal ions could remarkably alter the formation energy of Vo by the sequence of CsMnO (1.94 eV) < KMnO (1.97 eV) < NaMnO (2.07 eV) < ideal MnO 2 surface without the intercalated ion (2.23 eV). As a result, CsMnO with the most surface Vo sites could achieve efficient HCHO oxidation to CO 2 , with a HCHO consumption rate of about 0.149 mmol/(g•h) at 40 °C in 200 ppm HCHO/humid air [gas hourly space velocity = 80,000 mL/(g•h)]. Different from the Mars−van-Krevelen process, quantum chemical calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the main reaction pathway might be HCHO(ad) + [O](ad) → DOM → [HCOO − ] s → CO 2 via a Langmuir−Hinshelwood (L−H) mechanism. Alkali metals remarkably promoted the HCHO conversion by trapping oxygen through Vo sites and accelerating the facile reaction among adsorbed oxygen with adsorbed HCHO to deep degradation products (CO 2 and H 2 O).

CeNbO4.25 is reported to exhibit fast oxygen ion diffusion at moderate temperatures, making this the prototype of a new class of ion conductor with applications in a range of energy generation and storage devices. To date, the mechanism by which this ion transport is achieved has remained obscure, in part due to the long-range commensurately modulated structural motif. Here we show that CeNbO4.25 forms with a unit cell ∼12 times larger than the stoichiometric tetragonal parent phase of CeNbO4 as a result of the helical ordering of Ce(3+) and Ce(4+) ions along z. Interstitial oxygen ion incorporation leads to a cooperative displacement of the surrounding oxygen species, creating interlayer "NbO6" connectivity by extending the oxygen coordination number to 7 and 8. Molecular dynamic simulations suggest that fast ion migration occurs predominantly within the xz plane. It is concluded that the oxide ion diffuses anisotropically, with the major migration mechanism being intralayer; however, when obstructed, oxygen can readily move to an adjacent layer along y via alternate lower energy barrier pathways.

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Anionic metal−organic frameworks (MOFs) have attracted increasing attention due to the enhanced electrostatic interactions between their anionic frameworks and counter-ionic guests. Owing to these special host−guest interactions, anionic MOFs are beginning to have a large impact in the field of absorption and separation of ionic molecules and selective sensing of metal ions. Herein, two mesoporous anionic metal−organic frameworks, namely, [(CH 3 ) 2 NH 2 ] 6 [In 6 (OX) 6 (TCA) 4 ]•solvents (JOU-11) and [(CH 3 ) 2 -NH 2 ] 6 [In 6 (OX) 6 (TCPA) 4 ]•solvents (JOU-12) (H 3 TCA = tricarboxytriphenylamine; H 3 TCPA = tris((4-carboxyl)phenylduryl)amine; OX = oxalate), have been synthesized by using wheel-type [In 6 (OX) 6 -(COO) 12 ] 6− as building blocks. Structural analyses show that JOU-11 and JOU-12 show isoreticular three-dimensional frameworks with pyr topology. Due to their anionic frameworks and tunable pore window sizes, both compounds can be exploited for absorbing and separating cationic organic dyes. In addition, JOU-11 can be developed as a fluorescence "turn-off" sensor for selectively sensing Fe 3+ , whereas JOU-12 can be used for fluorescence "turn-on" sensing of Cu 2+ and Co 2+ ions.

Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO3 and iron doped SrTiO3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO3 and compared it to DOS of iron-doped SrTiO3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO3 and iron-doped SrTiO3. Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO3, are accessible only on TiO2 terminated SrTiO3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction.