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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]

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]

Pyridine molecules have been used as a catalyst to reduce the activation energy of the CO 2 reduction reaction. It has been reported that CO 2 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 CO 2 at low overpotential like pyridinium catalysts. Different thickness of P(4-VP) coated Pt electrodes were analyzed to determine the catalytic properties for CO 2 reduction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods showed the catalytic CO 2 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 CO 2 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 CO 2 reduction.