Abundant Surface Oxygen Vacancies Research Articles

Improved nickel nanocatalysts for selective cleavage of lignin model compounds and lignin

The selective hydrogenolysis of lignin offers a promising avenue for converting lignin into valuable chemicals and fuels. However, the development of highly active catalysts for this process remains challenging. In this study, a series of Nix/Al2O3 catalysts were synthesized by calcining and reducing layered double hydroxides (LDHs) precursors. These catalysts were evaluated for their effectiveness in catalyzing the conversion of lignin-derived model compounds (2-phenoxy-1-phenylethanol and diphenyl ether). Remarkably, the optimized Ni3/Al2O3 catalyst demonstrated exceptional performance in cleaving C–O bonds, achieving complete conversion with high selectivity for monomers product under reaction conditions of 200 °C, 1 MPa H2, and 1 h. The catalyst's outstanding performance can be attributed to its relatively large specific surface area, Ni loading exceeding 50 wt%, well-dispersed Ni metal particles, abundant surface oxygen vacancies, and a significant number of acid sites. Additionally, the hydrogenolysis of lignin using the Ni3/Al2O3 catalyst resulted in a substantial production of monophenols (15.0 wt%). This study introduces a novel approach for tailoring highly active Ni nanocatalysts and highlights the capability of Nix/Al2O3 catalysts to efficiently cleave C–O bonds in lignin under mild reaction conditions.

Dipole Moment and Built-In Polarization Electric Field Induced by Oxygen Vacancies in BiOX for Boosting Piezoelectric-Photocatalytic Removal of Uranium(VI).

Piezoelectric-photocatalysis is distinguished by its piezoelectricity as an external force that induces deformation within the catalyst to engender a polarized electric field compared to conventional photocatalysis. Herein, the piezoelectric photocatalyst BiOBr has been expertly synthesized via a plasma process and applied for piezoelectric-photocatalysis removal of uranium(VI) for the first time. The abundant surface oxygen vacancies (OVs) could induce a dipole moment and built-in electric field, which endows BiOBr with excellent separation and transport efficiency of photogenerated charges to actuate more charges to participate in the piezoelectric-photocatalytic reduction process. Consequently, under visible light and ultrasound (150 W and 40 kHz), the removal rate constant of OVs-BiOBr-30 (0.0306 min-1) was 2.4, 30.6, and 6 times higher than those of BiOBr (0.01273 min-1), ultrasound, or photocatalysis, respectively. The piezoelectric-photocatalytic synergy is also universal for BiOX (X = Cl, Br, or I) to accelerate the reduction rate of uranium(VI). This work highlights the role of piezoelectric-photocatalysis in the treatment of uranium-containing wastewater, which is of great significance for resource conservation and environmental remediation.

Controllable oxygen vacancies (in surface and bulk) to suppress the voltage decay of Li-rich layered cathode

Li-rich Mn-Based layered oxide is defined as a potential cathode material for its high specific capacity while several significant drawbacks such as inferior cycling stability and voltage decay limit its wide application. In this work, a suite of characterization techniques is employed to comprehensively investigate the crystal structure, surface morphology and chemical state of materials. The results suggest the successful preparation of layered oxide with controllable oxygen vacancies. Specifically, 1) Surface oxygen vacancies can act as a deterrent to irreversible oxygen release, consequently suppressing the voltage decay. 2) Stable lattice oxygen can enhance structural stability during cycling. 3) Swing-like sintering methodology and inducing surface oxygen vacancies technique are connected to synthesize the layered oxide with little lattice oxygen vacancies and abundant surface oxygen vacancies. The as-prepared cathode exhibits a commendable capacity retention of 85 %, and managed to alleviate the voltage attenuation significantly to 3.81 mV/cycle over 150 cycles at 0.5C. This concept of pre-constructing controllable oxygen vacancies provides important groundwork for developing Li-rich cathode with mitigated voltage decay and enhanced cycle life.

A H2O2 Oxidation Approach to Ti3C2/TiO2 for Efficient Photocatalytic Removal of Distinct Organic Pollutants in Water.

To develop versatile photocatalysts for efficient degradation of distinct organic pollutants in water is a continuous pursuit in environment remediation. Herein, we directly oxidize Ti3C2 MXene with hydrogen peroxide to produce C-doped anatase TiO2 nanowires with aggregates maintaining a layered architecture of the MXene. The Ti3C2 MXene provides a titanium source for TiO2, a carbon source for in situ C-doping, and templates for nanowire aggregates. Under UV light illumination, the optimized Ti3C2/TiO2 exhibits a reaction rate constant 1.5 times that of the benchmark P25 TiO2 nanoparticles, toward photocatalytic degradations of trace phenol in water. The mechanism study suggests that photogenerated holes play key roles on the phenol degradation, either directly oxidizing phenol molecules or in an indirect way through oxidizing first the surface hydroxyl groups. The unreacted Ti3C2 MXene, although with trace amounts, is supposed to facilitate electron transfer, which inhibits charge recombination. The unique nanostructure of layered aggregates of nanowires, abundant surface oxygen vacancies arising from the carbon doping, and probably the Ti3C2/TiO2 heterojunction guarantee the high photocatalytic efficiency toward removals of organic pollutants in water. The photocatalyst also exhibits an activity superior to, or at least comparable to, the benchmark P25 TiO2 toward photodegradations for typical persistent organic pollutants of phenol, dye molecule of rhodamine B, antibiotic of tetracycline, pharmaceutical wastewater of ofloxacin, and pesticide of N,N-dimethylformamide, when evaluated in total organic carbon removal.

Enhanced photocatalytic degradation by higher exposure of {110} facet and surface oxygen vacancies of BiOBr through cobalt doping strategy

Transition metal cobalt doped BiOBr (Co-BOB) was successfully synthesized by using hydrothermal method. The optimized Co-BOB achieved a remarkable rhodamine B degradation rate of 97 % in 30 min under visible light irradiation when initial concentration was 80 mg·L−1. Satisfactory removal efficiency was also observed under ambient sunlight irradiation and various water conditions. The cobalt doping strategy induced abundant surface oxygen vacancies formation (43.22 %) and resulted in an increasing exposure of {110} facets. The photosensitization and photocatalytic activities of Co-BOB significantly enhanced comparing with that of pure BiOBr. The synergy of Co doping and oxygen vacancies also induced the formation of a new band structure in Co-BOB. The synergistic effect promoted the efficient separation of photogenerated electrons and holes. By combining with density functional theory calculation, the RhB photocatalytic degradation mechanism by Co-BOB was proposed.

Effective degradation of quinoline by catalytic ozonation with MnCexOy catalysts: performance and mechanism.

Quinoline inevitably remains in the effluent of coking wastewater treatment plants due to its bio-refractory nature, which might cause unfavorable effects on human and ecological environments. In this study, MnCexOy was consciously synthesized by α-MnO2 doped with Ce3+ (Ce:Mn = 1:10) and employed as the ozonation catalyst for quinoline degradation. After that, the removal efficiency and mechanism of quinoline were systematically analyzed by characterizing the physicochemical properties of MnCexOy, investigating free radicals and monitoring the solution pH. Results indicated that the removal rate of quinoline was greatly improved by the prepared MnCexOy catalyst. Specifically, the removal efficiencies of quinoline could be 93.73, 62.57 and 43.76%, corresponding to MnCexOy, α-MnO2 and single ozonation systems, respectively. The radical scavenging tests demonstrated that •OH and •O2- were the dominant reactive oxygen species in the MnCexOy ozonation system. Meanwhile, the contribution levels of •OH and •O2- to quinoline degradation were about 42 and 35%, respectively. The abundant surface hydroxyl groups and oxygen vacancies of the MnCexOy catalyst were two important factors for decomposing molecular O3 into more •OH and •O2-. This study could provide scientific support for the application of the MnCexOy/O3 system in degrading quinoline in bio-treated coking wastewater.

Facile synthesis of NiCo2O4 nanostructures with abundant surface oxygen vacancies, and reduced content of Co and Ni valence states for the efficient and bifunctional electrochemical and photocatalytic oxidation of methylene blue

An abundant, low cost, scale up and ecofriendly method has been designed about the preparation of NiCo2O4 nanostructures and the electrode material was employed for the electrochemical oxidation and photocatalytic degradation of methylene blue (MB) under the irradiation of natural sunlight. The NiCo2O4 nanostructures prepared with and without spoiled bitter gourd juice were characterized with respect to morphology, crystalline quality, and surface chemical composition. The morphology of NiCo2O4 nanostructures was transformed from nanorod to low dimension nanoparticles using bitter gourd juice. The surface of NiCo2O4 nanostructures was enriched with the abundant surface oxygen vacancies and low content of different Co and Ni valence states using 10 mL of bitter gourd juice. The NiCo2O4 nanostructures obtained with the 10 mL of bitter gourd were observed highly electroactive towards the oxidation of MB in the phosphate buffer solution of pH 7.4. The linear working range of electrode material for the electrochemical oxidation of MB was estimated from 0.1 mM to 7 mM and a low limit of detection of 0.002 mM was found. A10 mL of bitter gourd juice assisted NiCo2O4 nanostructures were characterized by excellent selectivity, stability and reproducibility. Moreover, the NiCo2O4 nanostructures synthesized with the use of 10 mL of bitter gourd extract were also found active to degrade the MB in aqueous solution under the illumination of natural sunlight. The percent removal of MB was found almost 100 % for the time period of 210 min using NiCo2O4 nanostructures. The phytochemicals from spoiled bitter gourd juice has shown high potential to enhance the electrochemical and photocatalytic properties of NiCo2O4 nanostructures, thus it could be used for the preparation of new generation of electrode materials for the diverse applications.

Oxygen Release Suppression and Electronic Conductivity Enhancement for High Performance Li‐ and Mn‐Rich Layered Oxides Cathodes by Chalcogenide Redox Couple and Oxygen Vacancy Generations

AbstractLi‐ and Mn‐rich layered oxides (LMROs) are promising cathode materials for next‐generation lithium‐ion batteries (LIBs) due to their high capacity and high energy density. However, they suffer from severe capacity and voltage fading during cycling, where the irreversible oxygen release during cycle is deemed to a severe factor. Herein, this put forward a general oxygen release suppression strategy by introducing small amounts of sodium chalcogenides during cathode slurry preparation. The formed unstable surface peroxide ions O22− of LMRO during charging is reduced to stable O2− by chalcogen ion and couples the formation of sodium chalcogenic oxides, which is reduced to sodium chalcogenides and O2− during discharging. As a result, the oxygen release is significantly suppressed and the structural stability of LMRO is greatly enhanced. Meanwhile, abundant surface oxygen vacancies are generated coupling with evidently increased carrier concentration and mobility, thus enhancing electronic conductivity significantly. The Li1.2Ni0.13Co0.13Mn0.54O2 cathode with 3 wt% Na2Se shows a capacity retention as high as 96.2% and a capacity of 225 mAh g−1 after 500 cycles at 1 C, coupling with a high capacity of 135 mAh g−1 at 10 C. The relevant mechanism for the improved electrochemical properties is revealed, which is hopefully helpful for novel strategy design to high‐performance LMRO cathodes.

Surface exposure engineering on LaMnO3@Co2MnO4 for high-efficiency ethane catalytic combustion

Higher specific surface area and abundant surface oxygen vacancies are considered to be essential to the catalytic combustion. Herein, we elaborately fabricated an innovative catalyst on the basis of LaMnO3@Co2MnO4 under a controllable selective dissolution (SD) treatment for ethane catalytic combustion. La element in perovskite could effectively protect the spinel system as a sacrifice, with MnO2 covering on the spinel surface, thereby enhancing the activity and stability. In combination with XPS, in-situ DRIFT and various characterization results, this acid corrosion could provide induce better reducibility, larger specific surface area, higher Mn4+ and Co3+content and more oxygen vacancies, which played a significant role in promoting the adsorption, activation and decomposition of ethane. Among all as-prepared catalysts, the optimal performance for catalytic ethane combustion was achieved on LMO@CMO-10 catalyst. The T90 of LMO@CMO-10 was 341 °C under space velocity of 80,000 mL·g−1·h−1. This work not only fabricated the catalyst system with higher specific surface area and more oxygen vacancy by SD method, but also provided a potential strategy for the preparation of highly active catalysts.

Engineering oxygen vacancies on Tb-doped ceria supported Pt catalyst for hydrogen production through steam reforming of long-chain hydrocarbon fuels

Steam reforming of long-chain hydrocarbon fuels for hydrogen production has received great attention for thermal management of the hypersonic vehicle and fuel-cell application. In this work, Pt catalysts supported on CeO2 and Tb-doped CeO2 were prepared by a precipitation method. The physical structure and chemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, H2 temperature programmed reduction, and X-ray photoelectron spectroscopy. The results show that Tb-doped CeO2 supported Pt possesses abundant surface oxygen vacancies, good inhibition of ceria sintering, and strong metal-support interaction compared with CeO2 supported Pt. The catalytic performance of hydrogen production via steam reforming of long-chain hydrocarbon fuels (n-dodecane) was tested. Compared with 2Pt/CeO2, 2Pt/Ce0.9Tb0.1O2 and 2Pt/Ce0.5Tb0.5O2, the 2Pt/Ce0.7Tb0.3O2 has higher activity and stability for hydrogen production, on which the conversion of n-dodecane was maintained at about 53.2% after 600 min reaction under 700 oC at liquid space velocity of 9 ml·(g cat)–1∙h–1. 2Pt/CeO2 rapidly deactivated, the conversion of n-dodecane was reduced to only 41.6% after 600 min.

Modulation of Fe–MOF via second-transition metal ion doping (Ti, Mn, Zn, Cu) for efficient visible-light driven CO2 reduction to CH4

This study developed metal–organic frameworks (MOFs) with enhanced properties for CO2 conversion by doping second- transition metal ions (Ti, Mn, Zn, and Cu) into Fe–MOF, which resulted in Fe-M−MOF (M = Ti, Mn, Zn, or Cu). The selection of different metal species in the metal cluster nodes of the MOFs significantly impacted the CO2 conversion efficiency. Among the different combinations, the Fe–Cu bimetallic cluster node was identified as the most optimal node. In addition, we investigated various variables and preparation conditions for determining the optimal synthesis conditions for Fe–Cu-MOFs. We observed that a synthesis temperature, time, and pH of 130 °C, 15 h, and 3.2, respectively, yielded the best results. The 13CO2 isotope labeling method confirmed that the carbon source of CO and CH4 were derived from CO2. Under simulated visible-light irradiation (λ ≥ 420 nm), Fe–Cu-T130 exhibited the highest photocatalytic activity, with a CH4 generation rate of up to 444.2 μmol g−1 h−1. This high activity was attributed to several factors. First, the presence of Fe2+, Fe3+, and Cu2+ on the surface of Fe–Cu-T130 resulted in photogenerated electrons and holes under visible-light excitation. Fe2+ accepted electrons to reduce CO2, whereas Fe3+ and Cu2+ oxidized H2O through holes. Second, the polycrystalline structure of Fe–Cu-T130 with abundant surface oxygen vacancies enhanced the chemical reactivity. Finally, the low conduction band position and narrower bandgap of Fe–Cu-T130 facilitated the excitation of electrons into the conduction band, thereby promoting the CO2 reduction reaction. This study successfully demonstrated the enhanced photocatalytic activity of Fe–Cu-T130 for CO2 conversion under visible light. The findings provide insight into the development of MOFs with improved properties for the sustainable and efficient utilization of CO2.

Fabrication of Heterostructural FeNi3-Loaded Perovskite Catalysts by Rapid Plasma for Highly Efficient Photothermal Reverse Water Gas Shift Reaction.

Metal-semiconductor heterostructured catalysts have attracted great attention because of their unique interfacial characteristics and superior catalytic performance. Exsolution of nanoparticles is one of the effective and simple ways for in-situ growth of metal nanoparticles embedded in oxide surfaces and their favorable dispersion and stability. However, both high-temperature and a reducing atmosphere are required simultaneously in conventional exsolution, which is time-consuming and costly, and particles often agglomerate during the process. In this work, Ca0.9Ti0.8Ni0.1Fe0.1O3-δ (CTNF) is exposed to dielectric blocking discharge (DBD) plasma at room temperature to fabricate alloying FeNi3 nanoparticles from CTNF perovskite. FeNi3-CTNF has outstanding catalytic activity for photothermal reverse water gas shift reaction (RWGS). At 350°C under full-spectrum irradiation, the carbon monoxide (CO) yield of FeNi3-CTNF (10.78mmol g-1 h-1) is 11 times that of pure CaTiO3(CTO), and the CO selectivity is 98.9%. This superior catalytic activity is attributed to the narrow band gap, photogenerated electron migration to alloy particles, and abundant surface oxygen vacancies. The carbene pathway reaction is also investigated through in-situ Raman spectroscopy. The present work presents a straightforward method for the exsolution of nanoalloys in metal-semiconductor heterostructures for photothermal CO2 reduction.

Construction of coordination bond electron bridge boosting interfacial electron transfer to enhance bifunctional photocatalytic activity of TiO2/g-C3N4 heterojunction

The weak interfacial coupling of heterojunction catalysts leads to a large barrier, which inhibits interfacial electron transfer and limits the catalytic efficiency. Herein, a unique Ti-N coordination electron bridge has been designed and constructed in TiO2/g-C3N4 heterojunction with a tightly-coupled interface by using a newly designed topotactic transition and in-situ pyrolysis method. Experimental data and characterization analyses indicate that abundant stacking faults and surface oxygen vacancies change the surface atomic coordination environment and induce the formation of Ti-N coordination bond electron bridges. XPS, TA-PL probing experiment, and EPR analysis indicate a S-scheme electron transport mechanism. The synergistic effect of internal electric field and Ti-N electron bridge promote the efficient S-scheme electron transport, which facilitates the spatial separation of strong oxidizing holes and strong reducing electrons. The hierarchical nanoflower structure benefits electrolyte diffusion and reaction species adsorption. The above virtues endowed the catalyst with enhanced bifunctional photocatalytic activity for hydrogen evolution (1.89 mmol·g−1·h−1) and methyl blue degradation (0.114 min−1), which are 3.2 and 1.9 times that of the bare TiO2. This work opens a new avenue for the construction of heterojunctions and the optimization of interface carrier transfer, providing important insights for synthesizing photocatalysts with excellent activity and stability.

Enhanced degradation of micropollutants by visible light photocatalysts with strong oxygen activation ability

Visible light photocatalysis is widely considered a sustainable approach to break down micropollutants without chemical addition. To promote the output of photogenerated carriers under visible light, a Z-scheme plasmonic photocatalyst Bi-CeO2/Ag0/BiO2 was designed and fabricated to activate dissolved oxygen in water for micropollutant degradation. The doped Bi not only improved the separation of electron-hole, but also narrowed the band gap of CeO2 to enhance its absorption of visible light. Notably, metallic silver (Ag0) works as an electronic transmission vehicle from Bi-CeO2 to BiO2 in a Z-scheme mechanism. Likewise, the surface plasmon resonance effect of Ag0 also enhanced the absorption of visible light. Furthermore, the Bi doping induced abundant surface oxygen vacancies on CeO2 for enhanced capability and selectivity towards O2 adsorption and activation, which favored the generation of O2•− by photogenerated electrons to degrade sulfamethoxazole, enrofloxacin, and bisphenol A. Theoretical calculation results also confirmed the O2•−-driven degradation pathway for sulfamethoxazole. Therefore, the Z-scheme Bi-CeO2/Ag0/BiO2 not only extends the photocatalytic reactivity of CeO2-based catalysts to the visible light range, but also provides a chemical-free method to effectively degrade micropollutants.

Construction of a Fe2O3/Ti3C2Tx heterojunction photocatalyst with oxygen-rich vacancies and its photocatalytic properties

As a class of antibiotics, tetracycline (TC) poses a serious threat to aquatic environments, thereby necessitating new demands on their restoration. Herein, a Fe2O3/Ti3C2Tx heterojunction photocatalyst with abundant surface oxygen vacancies was prepared using a solvothermal method, which can promote the migration and separation of photogenerated electron–hole pairs and improve the catalytic degradation performance of the material. The experimental results revealed that the prepared Fe2O3/Ti3C2Tx heterojunction catalysts exhibited better TC degradation performance under simulated sunlight, corresponding to 2.5 times that of Fe2O3 and 5.1 times that of Ti3C2Tx. Fe2O3 and Ti3C2Tx formed a close contact interface, and the staggered energy-level structure achieved the rapid transfer of electrons, resulting in the formation of numerous oxygen vacancies during the conversion of Fe3+ to Fe2+; these oxygen vacancies not only changed the Fe2O3/Ti3C2Tx crystal structure but also provided additional active centers for the reaction. In addition, transient fluorescence spectroscopy and photocurrent experiments revealed that the method considerably improved the separation rate of photo‐excited carriers and the corresponding optoelectronic capability. The possible degradation pathways were revealed by the determination of the TC post-degradation by-products. Moreover, toxicity modeling results revealed that most degradation intermediates were less toxic than TC. This study discusses the importance of heterojunctions with oxygen-rich vacancies for improving the performance of degraded TC and provides an effective strategy for constructing heterojunction photocatalysts, broadening the applications of Fe2O3 and Ti3C2Tx materials in environmental remediation.

High-valence metal-doped amorphous IrOx as active and stable electrocatalyst for acidic oxygen evolution reaction

Proton-exchange membrane water electrolysis, particularly driven by renewable electricity, is a sustainable strategy for green hydrogen production. However, developing highly active and stable electrocatalysts to accelerate the oxygen evolution reaction (OER) remains challenging. Herein, we introduce an effective strategy for constructing high-valence metal-doped IrOx with abundant oxygen vacancies, while simultaneously enhancing the catalytic activity and stability of the acidic OER. The synthesized Ta-doped IrOx (350-Ta@IrOx) exhibits ultramicroscopic nanoparticle morphology and abundant surface oxygen vacancies</a>, enabling a rapid OER process with a low overpotential of 223 mV at 10 mA cm-2 and 147.7 times higher mass activity (1207.4 A gIr−1) than that of commercial IrO2 at 1.55 V</a> versus the reversible hydrogen electrode. More importantly, 350-Ta@IrOx affords excellent stability with insignificant potential degradation after 500 h of electrolysis at 10 mA cm2, originating from the low operating potential and suppressed dissolution and oxidation of oxygen vacancy active sites via Ta doping. Density functional theory calculations suggest that Ta doping and oxygen defect engineering are effective in facilitating the nucleophilic attack of water molecules, thereby accelerating the rate-determining step toward high catalytic OER activity on Ta-doped IrOx. We anticipate that this study will provide an effective method to obtain active and stable electrocatalysts via high-valence metal doping.

Surface engineering to tailor the active sites of SrTi0.9Co0.1O3-δ perovskite for CO oxidation

We successfully engineered the surface properties of SrTiO3 perovskite for a carbon monoxide (CO) oxidation catalyst by substituting Co ions (10 at.%) into Ti-sites in SrTiO3 and subsequently applying a reductive thermal treatment. The substitution of Co ions in SrTiO3 induced charge imbalance, which was compensated by the generation of oxygen vacancies. During the subsequent reductive thermal treatment process, lattice oxygen species were released from the lattice of SrTiO3, leading to the further formation of oxygen vacancies and the segregation of Co cations on the catalyst surface. Thus, SrTi0.9Co0.1O3-δ catalyst showed superior activity compared to the pristine SrTiO3 in CO oxidation, and its catalytic activity was further enhanced after the thermal treatment. This improvement was due to the abundant surface oxygen vacancies generated by Co substitution and reductive thermal treatment. The presence of a surface Co-enriched phase increased the concentration of Co at the catalyst surface, providing more adsorption sites for CO. These findings demonstrate the effective control of the active sites (oxygen vacancies and B-site cations) in SrTiO3 using the two-step surface engineering method. This research contributes to the design of perovskite-oxide catalysts with reaction-tailored active sites by exploiting the synergistic effect of substitution and reductive thermal treatment methods.

Combining heterointerface/surface oxygen vacancies engineering of bismuth oxide to synergistically improve its solar water splitting performance

Solar-powered photoelectrochemical (PEC) water splitting is recognized as a strategy for addressing fossil resource and global warming concerns. The purpose of this paper is to demonstrate for the first time a facile method to fabricate dendritic nanostructured (DN) Bi:Bi2O3 heterointerface engineering junctions that possess abundant surface oxygen vacancies (OVs, DN Bi:Bi2O3-OVs/FTO), with outstanding PEC performance. The surface OVs serve as shallow donors and active reaction sites, whereas the Bi-metal bridges are used for fast electron transport. Furthermore, surface OVs can enhance the surface features of Bi:Bi2O3 heterointerfaces and boost their electrical conductivity and donor density. This greatly enhances electrolyte ion and electron mobility, resulting in rapid water oxidation reactions at the Bi:Bi2O3/electrolyte interfaces. By combining the Bi:Bi2O3 heterointerface junction and surface OVs, we are able to create an effective photoanode with 95 % charge injection efficiency, applied bias photon-to-current efficiency (ABPE) of 0.112 %, and a photocurrent response of 0.334 mA.cm−2 at 1.23 V vs. the reversible hydrogen electrode (RHE), which represents improvements of about 4.5 and 10 folds over that of pure DN Bi2O3 photoanode. It is possible to construct a variety of unique nanostructured electrodes with adjustable optical and electronic properties to be used in solar cells, energy storage, and PEC applications.

Oxygen vacancy for boosted alkaline oxygen evolution under AC magnetic field

Reducing the overpotential of oxygen evolution reaction (OER) with slow kinetics is important to realize commercial hydrogen production from water electrolysis. Here, ZnCo2O4 with abundant surface oxygen vacancies is employed to clarify the influence of oxygen vacancies on OER performance under AC magnetic field. The additional active sites as well as enhanced reaction activity of each active sites resulting from oxygen vacancies enable N–ZnCo2O4-δ-350 to exhibit outstanding OER performance, where the overpotential is 406 mV at 10 mA cm−2. Furthermore, double exchange interaction between Co2+-O2--Co3+ ignited by oxygen vacancies produces ferromagnetism in N–ZnCo2O4-δ, which can directly promote OER under ACMF. And the mass transport at additional active sites active sites provided by oxygen vacancies is also accelerated under ACMF due to magnetohydrodynamic convection. As a result, non-iR-corrected overpotential at 10 mA cm−2 of N–ZnCo2O4-δ-350 is reduced to 243 mV when the ACMF intensity is 4.752 mT, which is a 44.5% reduction compared to no ACMF. These findings provide a novel and efficient perspective for realizing efficient electrocatalysis.

Elucidating the effect of Ce with abundant surface oxygen vacancies on MgAl2O4-supported Ru-based catalysts for ammonia decomposition

Ammonia is a promising COx-free hydrogen (H2) carrier because of its high volumetric H2 density. However, developing highly active/stable ammonia decomposition catalysts for H2 production remains challenging. In this study, the role of ceria (CeO2) as a promoter for Ru-based catalysts was investigated. Ru/Cex/MgAl(y00) catalysts were prepared by the incipient wetness impregnation (IWP) and deposition–precipitation (DP) methods. The surface oxygen vacancy (OV) concentration was controlled by the Ce loading and calcination temperature. By evaluating the surface reaction behavior of the ammonia decomposition catalysts, this study proposes that CeO2 effectively improves the recombination/desorption of N and H atoms. The optimal catalyst Ru/Ce5/MgAl(600) achieved a high H2 formation rate (27.4 mmolH2·gcat−1∙min−1 at 30,000 mL·gcat−1·h−1, 450 °C) and stable performance after exposure at 650 °C for 20 h. This study provides insight into the effect of abundant surface OVs in CeO2 on the physicochemical properties and ammonia decomposition performance of the catalysts.