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Controlling the number of oxygen vacancies (Vos) in metal‐oxide nanoparticles (MO NPs; TiO2, SnO2, and CeO2) using Li‐ions has been shown to endow MO NPs with improved photocatalytic and electrocatalytic properties. Increasing the number of Vos in nanostructures provides a foundation for efficient multi‐use catalyst designs that facilitate biomass oxidation reactions and improve electrocatalytic activity. Herein, the trends in the properties of MO‐based catalysts are investigated with varying amounts of Vos achieved by Li‐ion deposition. The controlled introduction of Vos into MO NPs tunes the band structures and surface chemistry, leading to enhanced activities of the NPs as photocatalysts for the selective oxidation of 2,5‐hydroxymethylfurfural and as electrocatalysts for acidic hydrogen evolution. It is believed that Li‐ion deposition in the MO matrix provides a novel approach for optimizing oxide‐based catalyst defect engineering, thereby enabling more efficient biomass conversion and water splitting. These findings contribute significantly to the field of multi‐purpose catalysis and are expected to inspire new catalyst designs for a more sustainable future. The results provide a pathway for the facile and efficient engineering of surface defect structures on catalytic metal oxide NPs toward designing high‐performance photocatalysts. [ABSTRACT FROM AUTHOR]

5‐Hydroxymethyl furfural (HMF) obtained from biomass can be converted to 2,5‐diformylfuran (DFF), a valuable chemical intermediate. However, the typical HMF oxidation process requires energy consumption such as high temperature and oxygen pressure. Herein, Au2S decorated CdS nanowires (denoted as Au2S@CdS NWs) are fabricated by a simple ion exchange method and applied as a heterostructure photocatalyst system for HMF oxidation under mild conditions. Under visible light irradiation, the photocatalytic performance of Au2S@CdS NWs is significantly enhanced compared with pristine CdS NWs, in which Au2S (0.25%)@CdS NWs achieve the high DFF yield (≈95%) for 4 h reaction time. This result means that the heterogeneous interface formed between CdS NWs and Au2S promotes the separation efficiency of photogenerated charges, which leads to high catalytic activity. Moreover, Au2S (0.25%)@CdS NWs work well for HMF conversion to DFF under anaerobic and aerobic conditions. Control experiments and characterization are conducted to investigate each reaction mechanism. Consequently, it is found that the photogenerated hole directly oxidizes HMF to DFF under anaerobic conditions and the 1O2 produced from oxygen is the active species for HMF conversion to DFF under aerobic conditions. [ABSTRACT FROM AUTHOR]

The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) has been studied extensively. However, the short lifetime of catalytic electrodes remains a challenge for the electrocatalytic HMF oxidation reaction, and the high pH of the electrolyte causes denaturation of HMF during the reaction. Herein, deep eutectic solvents (DES) are employed for the preparation of efficient and durable catalytic electrodes for HMF oxidation. The catalytic electrode made up of DES avoided the complexity of multiple alkylations leading to 99% HMF conversion affording FDCA in 85.3% yield with high durability, due in part to the lower pH of the electrolyte. [ABSTRACT FROM AUTHOR]

In this study, 2-pyrone-4,6-dicarboxylic acid (PDC), a valuable monomer for bio-degradable plastics, was synthesised using terephthalic acid (TPA) derived from PET waste by a comprehensive chemo-microbial hybrid process. Depolymerisation of PET into TPA was performed via microwave-assisted hydrolysis using biomass-derived SiO2 catalysts with thiol functionalisation. The increased PET hydrolysis efficiency was investigated by reaction kinetics studies. The conversion of TPA obtained by depolymerisation of PET waste into PDC was achieved using two recombinant Escherichia coli strains expressing tphAabc and tphB genes for TPA degradation into protocatechuic acid (PCA) through 3,4-dihydroxy-cyclohexa-1,5-diene-1,4-dicarboxylic acid (DCD) (E. coli PCA strain) and using ligABC genes to convert PCA to PDC through 4-carboxy-2-hydroxymuconate semialdehyde (CHMS) (E. coli PDCPCA strain). Based on the high chemical depolymerisation of PET waste into TPA (over 97% efficiency), the double-catalyst system composed of the E. coli PCA strains with TPA degradation module and PDC synthesis module enables PET waste to be used in the PDC production platform with 96.08% of the overall efficiency. [ABSTRACT FROM AUTHOR]

2,5-furandicarboxylic acid (FDCA), one of the key building block for replacing petroleum-derived tereph-thalic acid, is utilized as the source of bioplastics, pharmaceuticals. Herein, free-standing Cu(OH)2 and CuO nanowires as electrode were examined to disclose the effects of crystal structure and chemical formation based on copper oxide in electrocatalytic 5-Hydroxymethylfurfural (HMF) oxidation to FDCA in 0.1 M KOH solution. We introduced on three-dimensional copper foam (CuF) with high porosity as copper source and substrate with high conductivity free-standing Cu(OH)2 and CuO nanowires (NWs) on the substrate by inorganic polymerization and calcination for electrochemical HMF oxidation. This was enabled by square-planar coordination (σx2-y2) of Cu2+ ions in (001) crystal faces of Cu(OH)2 crystal. As a result of stacking with hydrogen bonds, free-standing Cu(OH)2 NWs on the substrate was formed. There was no change in the morphology of the nanowire arrays, but the active sites from a plane area per surface-exposed Cu atoms by transformation of Cu(OH)2 to CuO NWs increased. [ABSTRACT FROM AUTHOR]

Pyridine molecules have been used as a catalyst to reduce the activation energy of the CO2 reduction reaction. It has been reported that CO2 is reduced by pyridine catalysts at low overpotential around −0.58 V vs. SCE. Poly(4-vinylpyridine), which has pyridine functional groups shows similar catalytic properties to reduce CO2 at low overpotential like pyridinium catalysts. Different thickness of P(4-VP) coated Pt electrodes were analyzed to determine the catalytic properties for CO2 reduction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods showed the catalytic CO2 reduction properties of a P(4-VP)/Pt electrode. Thin P(4-VP)/Pt film showed a low current density of −0.16 mA cm−2 under CO2 atmosphere and the current density reached −0.45 mA cm−2 with increase of the P(4-VP) thickness. The increase of current density was explained by an increased surface concentration of adsorbed pyridinium groups of the thick P(4-VP) layer. Nyquist plots also showed decrease of impedance with increase of the P(4-VP) layer indicating fast charge transfer between Pt and the P(4-VP) layer due to the increase of hybrid ionic complex formation on the Pt surface. However, charge transfer is restricted when the P(4-VP) layer becomes more thick because of slowed protonation of pyridine groups adjacent to the Pt surface due to the suppressed permeability of electrolyte solution into the PVP membrane. This electrochemical observation provides a new aspect of P(4-VP) polymer for CO2 reduction. [ABSTRACT FROM AUTHOR]

A (040)-crystal facet engineered BiVO4 ((040)-BVO) photoanode is investigated for solar fuel production. The (040)-BVO photoanode is favorable for improved charge carrier mobility and high photocatalytic active sites for solar light energy conversion. This crystal facet design of the (040)-BVO photoanode leads to an increase in the energy conversion efficiency for solar fuel production and an enhancement of the oxygen evolution rate. The photocurrent density of the (040)-BVO photoanode is determined to be 0.94 mA cm−2 under AM 1.5 G illumination and produces 42.1% of the absorbed photon-to-current conversion efficiency at 1.23 V (vs RHE, reversible hydrogen electrode). The enhanced charge separation efficiency and improved charge injection efficiency driven by (040) facet can produce hydrogen with 0.02 mmol h−1 at 1.23 V. The correlation between the (040)-BVO photoanode and the solar fuel production is investigated. The results provide a promising approach for the development of solar fuel production using a BiVO4 photoanode. [ABSTRACT FROM AUTHOR]

The photocatalysis, chromism, and sensing capabilities of nanostructured tungsten oxides, such as tungsten trioxide (WO3), its suboxides (WOx, 0 ＜ x ＜ 3) and hydrates (WO3·nH2O, n = 1/3 (0.33), 0.5, 0.75, 1, 2, etc.), tungsten bronzes MxWO3 (M = Li, Na, K, Rb, Cs and NH4), and metal tungstates (such as Bi2WO6 and CuWO4) have attracted much attention. To improve these properties, many strategies have been pursued, such as morphology control, doping, and heterostructuring. Crystal facet engineering has recently become a very important method of fine-tuning the physicochemical properties of semiconductors. The photocatalytic reactivity of a photocatalyst is significantly affected by its surface environment, including its surface electronic and atomic structures, which strongly depend on the crystal facets. It is believed that crystals with different exposed facets will have different properties, with the exposure of highly activated facets enhancing the photocatalytic and sensing properties. This article describes the syntheses of 2D WO3 crystals with the {002} facet primarily exposed, octahedral WO3 or WO3·nH2O with exposed {111} facets, and WO3 films with dominant orientations, such as orientation along the {002} facet. WO3 doping, WO3-based heterostructuring and their applications are also presented in this paper. [ABSTRACT FROM AUTHOR]

An ultrathin SiO2 under-layer was inserted between the FTO substrate and the Ti-doped hematite film to suppress the reverse electron recombination from the FTO substrate to the hematite layer for improved photoelectrochemical activity of the hematite film during the photoelectrochemical (PEC) water splitting reaction. The reverse current of the SiO2 under-layered hematite thin film decreased from −0.075 mA cm−2 to −0.035 mA cm−2, with enhanced interfacial charge transfer and internal charge transport efficiencies. The hematite film with the ultrathin SiO2 under-layer showed a promising photocurrent density of 0.76 mA cm−2 at 1.23 V vs. RHE under 1 sun illumination without hole scavenger materials during the PEC water splitting reaction. [ABSTRACT FROM AUTHOR]

Fluorine doped tin oxide (FTO) is widely used as a substrate in the synthesis of a photo-reactive semiconductor electrode for solar water splitting. The hematite film on the surface of the FTO substrate annealed at 700 °C showed an enhanced photocurrent value with a maximum photocurrent of 0.39 mA cm−2 at 1.23 V vs. RHE under 1 sun illumination. This is a much enhanced photocurrent value of the hematite films than that of those annealed at temperatures lower than 700 °C. This is a promising approach for the enhancement of the photoelectrochemical properties of metal oxide thin films. This work reports on the mechanism of the annealing process of the synthesized hematite film to enhance the photocurrent value. Furthermore, this can be used for the enhanced efficiency of the solar water splitting reaction. [ABSTRACT FROM AUTHOR]

To improve the optoelectronic properties of hematite film as a photoanode, hematite film was orientated on the (012) plane by the secondary growth of organized microcrystals. The resultant film showed promising photoelectrochemical effects compared with a randomly oriented one, with a maximum photocurrent of 0.8 mA cm−2 at 1.23 V vs. RHE under the illumination of 1 sun. [ABSTRACT FROM AUTHOR]

Manganese-doped hematite nanocrystals were synthesized by hydrothermal method and study on the activity of photocatalytic properties by different Mn ratio. From the crystal structure and optical study, the oxidation state of the manganese-doped hematite crystals was modulated by doping. The activity of samples (M1–M3) was tested by photodegradation of methyl orange dye in the presence of manganese-doped hematite as photocatalyst. [ABSTRACT FROM AUTHOR]

Correction for 'Facile fabrication and photoelectrochemical properties of a one axis-oriented NiO thin film with a (111) dominant facet' by Chang Woo Kim et al., J. Mater. Chem. A, 2014, 2, 19867-19872. [ABSTRACT FROM AUTHOR]