Abundant Oxygen Vacancies Research Articles

Photocatalytic removal of organic pollutants by SiO2 modified BiOCl nanosheets with abundant oxygen vacancies

In this demonstration, SiO2/BiOCl composites were fabricated by loading SiO2 nanoparticles onto the surface of BiOCl nanosheets through a conventional hydrothermal approach. SiO2/BiOCl photocatalysts were studied by specific surface area analysis, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS) and electron spin resonance (ESR) techniques. In light of the rich pore structures of BiOCl modified by SiO2, the photogenerated carriers separation efficiency of SiO2/BiOCl is significantly improved. Therefore, SiO2/BiOCl composite nanosheets show high efficiency towards degradation of perfluorooctanoic acid (PFOA) and rhodamine B (RhB), and the composites display exceptional stability. In comparison to the pure BiOCl, photocatalytic degradation activity of 4.4 % SiO2/BiOCl (mass ratio of SiO2/Bi(NO3)3·5H2O is 4.4 %) for RhB and PFOA increases by 100 % and 50 %, respectively. The result from the radical capture experiments suggests that holes (h+) and superoxide radicals (·O2–) play a crucial role as the primary active species in degradation of organic pollutants. The enhanced photocatalytic efficiency of the SiO2/BiOCl composites can be primarily ascribed to the construction of numerous oxygen vacancies (OVs), which effectively promote the adsorption of organic pollutants, boost light responsiveness, and expedite the separation of photoinduced e-/h+ pairs.

Mesoporous NiCo2O4 microspheres combining abundant oxygen vacancies for high-performance xylene gas sensor

In this study, the mesoporous NiCo2O4 microspheres with abundant oxygen vacancies were prepared through a concise solvothermal-calcination method. The result revealed that the mesoporous 500-NiCo2O4 sensor showed a high gas sensing response of 16.7 to 100 ppm xylene, and rapid response-recovery process and long-term stability. These can be attributed to the synergistic effect between mesoporous structure and oxygen vacancy, which not only facilitated the gas adsorption–desorption process but also offered more active sites to ionize more oxygen species, leading to an efficient gas sensing reaction.

Bimetallic Fe-Mn loaded H-ZSM-5 zeolites for excellent VOCs catalytic oxidation at low-temperatures: Synergistic effects and catalytic mechanisms

The development of catalysts with high adsorption and low-temperature catalytic characteristics for the decomposition of volatile organic compounds (VOCs) is of great importance for air purification. Herein, H-ZSM-5 (proton form Zeolite Socony Mobil-5) zeolite -supported Fe-Mn elements were synthesized via a two-step procedure (hydrothermal and precipitation methods). These zeolite-supported bimetal Fe-Mn catalysts exhibited a mesoporous structure, uniform distribution of Fe-Mn elements, excellent catalytic-oxidation capacity for toluene at low-temperatures, and high stability. Due to interactive synergies between the bimetallic Fe and Mn, the Fe2-Mn1/H-ZSM-5 (ratio of Fe and Mn was 2:1 with a total amount of 15 % to H-ZSM-5) exhibited 100 % toluene-conversion at 200 °C and T90 = 195 °C (temperature of toluene-conversion at 90 %) with GHSV = 20,000 mL/(g∙h). Its distinguishing catalytic-oxidation abilities at low temperatures were due to abundant oxygen-vacancies, adequate acidic-sites and various active oxygen-species, which improved the adsorption of toluene and expedited its degradation. The Fe2-Mn1/H-ZSM-5 catalyst also demonstrated a good resistance to humidity and renewable catalytic properties over five cyclic tests. The in-situ DRIFTS and LC-MS results revealed that toluene was decomposed to benzyl-alcohol, benzaldehyde, benzoate-acid, formates or/and acetate step by step, and finally CO2 and H2O. The mechanism of toluene oxidation over Fe2-Mn1/H-ZSM-5 catalysts was proposed and elucidated via the Mars–van-Krevelen (MVK) model. This study comprehensively explored the adsorption and decomposition kinetics of VOCs over bimetal decorated H-ZSM-5, which was useful toward the design of highly efficient catalysts for the removal of VOCs.

Fe and Cu Double-Doped Co3O4 Nanorod with Abundant Oxygen Vacancies: A High-Rate Electrocatalyst for Tandem Electroreduction of Nitrate to Ammonia.

The electrochemical nitrate reduction reaction (NO3RR) is an attractive green alternative to the conventional Haber-Bosch method for the synthesis of NH3. However, this reaction is a tandem process that involves multiple steps of electrons and protons, posing a significant challenge to the efficient synthesis of NH3. Herein, we report a high-rate NO3RR electrocatalyst of Fe and Cu double-doped Co3O4 nanorod (Fe1/Cu2-Co3O4) with abundant oxygen vacancies, where the Cu preferentially catalyzes the rapid conversion of NO3- to NO2- and the oxygen vacancy in the Co3O4 substrate can accelerate NO2- reduction to NH3. In addition, the introduction of Fe can efficiently capture atomic H* that promotes the dynamics of NO2- to NH3, improving Faradaic efficiency of the produced NH3. Controlled experimental results show that the optimal electrocatalyst of Fe1/Cu2-Co3O4 exhibits good performance with high conversion (93.39%), Faradaic efficiency (98.15%), and ammonia selectivity (98.19%), which is significantly better than other Co-based materials. This work provides guidance for the rational design of high-performance NO3RR catalysts.

Sulfidation of CoCuOx Supported on Nickel Foam to Form a Heterostructure and Oxygen Vacancies for a High-Performance Anion-Exchange Membrane Water Electrolyzer.

Anion-exchange membrane water electrolyzer (AEMWE) is attracting attention for hydrogen production owing to its ability to employ nonprecious metal catalysts and high energy conversion efficiency. Spinel-structured transition metal oxides exhibit excellent potential in oxygen evolution reaction (OERs). Nevertheless, the research on highly active and durable spinel-structured electrodes for the anodic OER of AEMWE is deficient. Herein, a self-supported S-CoCu oxide/nickel foam (S-CoCuOx/NF) anode was synthesized through a two-step method (electrodeposition and sulfidation). The formation of abundant oxygen vacancies and heterostructure collaboratively enhances the electron and mass transfer, resulting in an overpotential of 313 mV at 100 mA cm-2 for OER. For the lab-scale AEMWE system with the S-CoCuOx/NF anode, a current density of 1 A cm-2 was obtained at 1.87 V (cell voltage) with high durability for 110 h (1 A cm-2) at 60 °C. The results will provide insights into developing the spinel structure-derived anode for high-performance AEMWE.

Activation of peroxymonosulfate by Cu–Ni–Fe layered double oxides for degradation of butyl 4-hydroxybenzoate: Synergistic effect of oxygen vacancy and Cu(I)

In this study, Cu hybridization coupling oxygen defect engineering was adopted to synthesis of CuNiFe layered double oxides (CuNiFe-LDOs) in peroxymonosulfate (PMS) activation for degradation of methyl 4-hydroxybenzoate. The morphology and crystal structure of CuNiFe-LDOs was characterized in detail, which exhibited regular layered-structure at a Cu:Ni doping ratio of 1:1 and annealing temperature of 400 °C, and presented the crystal of CuxO@Fe3O4–NiO. Besides, the X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) results demonstrated that abundant oxygen vacancies (OVs) and low oxidation state Cu species were composed in CuNiFe-LDOs400. The Cu1·5Ni1·5Fe1-LDOs400/PMS system showed excellent catalytic performance toward the degradation of butyl 4-hydroxybenzoate (BuP), and resistant to the effect of pH value and background inorganic anions. Based on quenching experiments and EPR measurements, singlet oxygen (1O2) was identified as the dominant active species during the heterogeneous catalytic process, which was generated by the synergistic interaction between OVs-Cu(I) site and PMS. In this process, the electron-drawing property of OVs promoted the adsorption of PMS molecule on Cu(I) site, followed by the accumulation of electron and cleavage of O–O bond to generate intermediate oxygen radical species, which donated one electron to eventually generate singlet oxygen.

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.

Design of hollow copper nanospheres/reduced graphene oxide nanocomposites for high performance catalytic reduction of p-nitrophenol

The development of functional materials for catalysis applications is a continuing issue, particularly in aqueous-phase catalysis. The creation of inexpensive catalysts with improved catalytic activity is still difficult. In this study, the hollow structured Cu nanospheres decorated on the reduced graphene oxide sheets (h-CuNS/rGO) nanocomposites were successfully prepared and applied in the catalytic reduction of p-nitrophenol (p-NP) in water using sodium borohydride as the reducing agent to obtain industrially useful p-aminophenol (p-AP) within a short time. The structure and morphology of h-CuNS/rGO were studied in order to get a full knowledge of the mechanism underlying the creation of its distinctive hollow structure. In the reduction of p-NP, the h-CuNS/rGO demonstrated significant catalytic activity and reusability. The catalytic hydrogenation mechanism on the surface of h-CuNS/rGO was shown to exhibit a synergistic effect between the catalytic h-CuNS and the supporting rGO. The hollow structure, abundant oxygen vacancies as well as the supported rGO worked together to enhance the catalytic activity during p-NP reduction. Therefore, this work proposes a strategy for the simple synthesis of nanocatalyst with high catalytic performance, which endows the potential applications including catalysis.

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.

La, Ce co-doped In2O3 hierarchical microstructure with high sensing performance towards n-butanol

Dual rare earth (La/Ce) doped In2O3 hierarchical microstructures are prepared by a hydrothermal method followed by calcination. Various combination amounts of La and Ce are systematically investigated via a climbing method to determine an optimized co-doping sample. Characterization results indicate that doping enables to distort crystal structure, leading to hierarchical morphology with large surface area, abundant surface defects and oxygen vacancy. Gas sensing tests reveal that co-doping into In2O3 significantly improves the sensing performance towards n-butanol. The La1Ce4.5-In2O3 sample has the highest sensing response (143) towards 100 ppm n-butanol at the optimized temperature of 280 °C, which is 8.0, 4.3 and 1.4 times higher than that of the pristine In2O3, La1-In2O3 and Ce4.5-In2O3, respectively. To deeply understand the enhanced sensing mechanism, electrochemical experiments are conducted. The high sensing performance of La1Ce4.5-In2O3 can be attributed to: (1) its optimized band structure, (2) large carrier density, (3) low charge transfer resistance, and (4) strong redox activity on the surface of materials.

Activation of peroxymonosulfate by biochar in-situ enriched with cobalt tungstate and cobalt: Insights into the role of rich oxygen vacancies and catalytic mechanism

The development of low-cost, stable, and recyclable multiphase catalysts in advanced oxidation process is essential for efficient degradation of antibiotics. In this study, a BC-Co-W-700 catalyst was used to activate peroxymonosulfate (PMS) for chlortetracycline (CTC) degradation. The catalyst was prepared using reclaimed biomass material as a matrix. The biochar-based catalyst possessed abundant active sites and realized the in-situ growth of Co and CoWO4. The BC-Co-W-700/PMS achieved 100% degradation of CTC (20 mg/L) within 18 min. Quenching and electron paramagnetic resonance experiments were conducted to investigate the reactive oxygen species (ROS) in the BC-Co-W-700/PMS system. The identified ROS in this system included 1O2, O2−, SO4−, and OH. Abundant ROS endowed the system with strong degradation performance, applicability, and anti-interference ability. The catalytic mechanism of BC-Co-W-700/PMS system was comprehensively investigated using a combination of electrochemical experiments and theoretical calculations. The in-situ pyrrolic N formed by biochar had a strong adsorption capacity for CTC, allowing pollutants to quickly adsorb to the catalyst surface. This greatly shortened the distance required for the catalytic reaction. The introduction of W led to abundant oxygen vacancies on BC-Co-W-700, causing the catalyst to produce a large amount of 1O2. Furthermore, the oxygen vacancies provided a high concentration of electrons for the conversion of Co3+/Co2+. In addition, CTC degradation pathways were analyzed using density functional theory calculations, and the toxicity of the intermediates was evaluated using the quantitative structure–activity relationship combined with experiments. The green catalyst synthesis method proposed in this paper could provide a new approach for the efficient degradation of antibiotics in wastewater.

Tuning the crystalline and electronic structure of ZrO2 via oxygen vacancies and nano-structuring for polysulfides conversion in lithium-sulfur batteries

The recent emergence of tetragonal phases zirconium dioxide (ZrO2) with vacancies has generated significant interest as a highly efficient and stable electrocatalyst with potential applications in trapping polysulfides and facilitating rapid conversion in lithium-sulfur batteries (LSBs). However, the reduction of ZrO2 is challenging, even under strong reducing atmospheres at high temperatures and pressures. Consequently, the limited presence of oxygen vacancies results in insufficient active sites and reaction interfaces, thereby hindering practical implementation. Herein, we successfully introduced abundant oxygen vacancies into ZrO2 at the nanoscale with the help of carbon nanotubes (CNTs-OH) through hydrogen-etching at lower temperatures and pressures. The introduced oxygen vacancies on ZrO2−x/CNTs-OH can effectively rearrange charge distribution, enhance sulfiphilicity and increase active sites, contributing to high ionic and electronic transfer kinetics, strong binding energy and low redox barriers between polysulfides and ZrO2−x. These findings have been experimentally validated and supported by theory calculations. As a result, LSBs assembled with the ZrO2−x/CNTs-OH modified separators demonstrate excellent rate performance, superior cycling stability, and ultra-high sulfur utilization. Especially, at high sulfur loading of 6 mg cm−2, the area capacity is still up to 6.3 mA h cm−2. This work provides valuable insights into the structural and functional optimization of electrocatalysts for batteries.

Defect Engineered Metal–Organic Framework with Accelerated Structural Transformation for Efficient Oxygen Evolution Reaction

AbstractMetal–organic frameworks (MOFs) have been increasingly applied in oxygen evolution reaction (OER), and the surface of MOFs usually undergoes structural transformation to form metal oxyhydroxides to serve as catalytically active sites. However, the controllable regulation of the reconstruction process of MOFs remains as a great challenge. Here we report a defect engineering strategy to facilitate the structural transformation of MOFs to metal oxyhydroxides during OER with enhanced activity. Defective MOFs (denoted as NiFc′xFc1‐x) with abundant unsaturated metal sites are constructed by mixing ligands of 1,1′‐ferrocene dicarboxylic acid (Fc′) and defective ferrocene carboxylic acid (Fc). NiFc′xFc1‐x series are more prone to be transformed to metal oxyhydroxides compared with the non‐defective MOFs (NiFc′). Moreover, the as‐formed metal oxyhydroxides derived from defective MOFs contain more oxygen vacancies. NiFc′Fc grown on nickel foam exhibits excellent OER catalytic activity with an overpotential of 213 mV at the current density of 100 mA cm−2, superior to that of undefective NiFc′. Experimental results and theoretical calculations suggest that the abundant oxygen vacancies in the derived metal oxyhydroxides facilitate the adsorption of oxygen‐containing intermediates on active centers, thus significantly improving the OER activity.

Defect Engineered Metal-Organic Framework with Accelerated Structural Transformation for Efficient Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) have been increasingly applied in oxygen evolution reaction (OER), and the surface of MOFs usually undergoes structural transformation to form metal oxyhydroxides to serve as catalytically active sites. However, the controllable regulation of the reconstruction process of MOFs remains as a great challenge. Here we report a defect engineering strategy to facilitate the structural transformation of MOFs to metal oxyhydroxides during OER with enhanced activity. Defective MOFs (denoted as NiFc'x Fc1-x ) with abundant unsaturated metal sites are constructed by mixing ligands of 1,1'-ferrocene dicarboxylic acid (Fc') and defective ferrocene carboxylic acid (Fc). NiFc'x Fc1-x series are more prone to be transformed to metal oxyhydroxides compared with the non-defective MOFs (NiFc'). Moreover, the as-formed metal oxyhydroxides derived from defective MOFs contain more oxygen vacancies. NiFc'Fc grown on nickel foam exhibits excellent OER catalytic activity with an overpotential of 213 mV at the current density of 100 mA cm-2 , superior to that of undefective NiFc'. Experimental results and theoretical calculations suggest that the abundant oxygen vacancies in the derived metal oxyhydroxides facilitate the adsorption of oxygen-containing intermediates on active centers, thus significantly improving the OER activity.

Efficient peroxymonosulfate activation by Aurivillius phase Bin+1Fen-3Ti3O3n+3(n = 4, 5, 6) for wastewater purification

Aurivillius phase layered perovskites, Bin+1Fen-3Ti3O3n+3(n = 4, 5, 6), have been deemed as promising photocatalysts for degrading organic pollutants in wastewater. However, the inferior photocatalytic performance has greatly limited its application. Here, Bin+1Fen-3Ti3O3n+3 (n = 4, 5, 6) nano-shelves were fabricated and applied as heterogeneous photocatalysts in peroxymonosulfate (PMS) activation for tetracycline hydrochloride degradation. Compared with Bin+1Fen-3Ti3O3n+3(n = 4, 5, 6), the Bin+1Fen-3Ti3O3n+3(n = 4, 5, 6)/PMS system demonstrated an excellent enhancement for tetracycline hydrochloride removal under visible light illumination. Among the synthesized photocatalysts, Bi7Ti3Fe3O21/PMS showed the highest catalytic activity, with the calculated kinetic constant reaching as high as 0.0394 min−1, which was about 78.8 higher than that of Bi7Ti3Fe3O21. The improved tetracycline hydrochloride degradation performance of Bi7Ti3Fe3O21/PMS is attributed to the presence of abundant oxygen vacancies in Bi7Ti3Fe3O21, which can not only boost the separation of electron-hole pairs but also facilitate PMS activation and radical generation. Besides, the scavenging experiments and electron spin resonance analysis showed that sulfate radicals, superoxide radicals, hydroxyl radicals, and holes could effectively degrade tetracycline hydrochloride. Overall, these findings are beneficial for understanding the mechanism of PMS activation by Aurivillius phase layered perovskites-based catalysts and are helpful for the practical application of sulfate-based technology for wastewater purification.

Perovskite Oxides Alleviate Microstrain and Anion Loss of Radially-Aligned Ni-Rich Ncm811 Cathodes under High-Voltage Operations.

The energy density of Ni-rich cathodes is expected to be further unlocked by increasing the cut-off voltage to above 4.3V, which nevertheless come with significantly increased irreversible phase transition and abundant side reactions. In this study, the perovskite oxides enhanced radial-aligned LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathodes are reported, in which the coherent-growth La2 [LiTM]O4 clusters are evenly riveted into the crystals and the stable Lax Ca1- x [TM]O3- x protective layer is concurrently formed on the surface. The reciprocal interactions greatly reduce the lattice strain during de-/lithiation. Meantime, the abundant oxygen vacancies of the coating layer are proved to reversibly capture (state of charge) and re-release (state of discharge) the oxygen radicals, fully avoiding their correlative side reactions. The resultant NCM811 displays negligible O2 and CO2 emissions when charging to 4.5V as well as a thinner CEI film, therefore delivering a large capacity of 225 mAh g-1 at 0.1C in coin-type half-cells and a high retention of 88.3% after 1000 cycles at 1C in pouch-type full-cells within 2.7-4.5V. The development of high-voltage Ni-rich cathodes exhibits a highly effective pathway to further increase their energy density.

Ultra-efficient electrooxidation of ethylene glycol enable by Pd-loaded Fe-doped Nb2O5 with abundant oxygen vacancies

Niobium pentoxide (Nb2O5) has emerged as a highly promising electrocatalyst for ethylene glycol oxidation reaction (EGOR) due to its eco-friendly nature and its ability to maintain structural stability in alkaline environments. However, its inherent electronic structure has posed a significant barrier to further enhancing of EGOR activity. In this study, we successfully synthesized Pd-based electrocatalysts by incorporating Fe-doped Nb2O5 with abundant oxygen vacancies (Pd/FNO-2.5), which effectively promoted ethylene glycol oxidation. The results showed that the introduction of Fe doping not only altered the electronic structure of Nb2O5, leading to the generation of oxygen vacancies, but also decreased the d-band center of Pd, thereby reducing thermodynamic energy barrier of the rate-determining step by approximately 0.58 eV. Impressively, the Pd/FNO-2.5 catalyst demonstrated remarkable electrocatalytic performance exhibiting a relatively low initial potential (−0.11 V) and high mass activity (0.380 A mg−1Pd). Furthermore, even after undergoing 100 consecutive recycling experiments, the Pd/FNO-2.5 catalyst still retained 81.10 % of its current density. This study demonstrates that doping-induced oxygen vacancy engineering is a promising approach for developing efficient EGOR electrocatalysts for direct ethylene glycol fuel cells, which is associating with the efficient and sustainable development of fuel cell and the carbon neutrality efforts.

Crystal-facet-dependent activity and N2 yield of Ag/CeO2 catalysts for catalytic oxidation of N, N-Dimethylformamide

Shape-controlled CeO2 with different exposed crystal facets, CeO2 nanorods (110) and (100), nanocubes (100) and nano-octahedrons (111), were prepared as supports of Ag and then the catalytic oxidation of N, N-dimethylformamide (DMF) was investigated. Ag/CeO2 nanorod (Ag/r-Ce) catalyst exhibits better dispersion of Ag species due to the abundant oxygen vacancies of CeO2 (110) with outstanding anchoring effect, meanwhile, more Ag-O-Ce interfaces and Ag+ species are achieved because of the strong metal-support interaction and easy migration of oxygen species between Ag and CeO2 (110). Ag/r-Ce catalyst exhibits excellent catalytic activity (T90 =158 °C), 100% yield of CO2 at 240 °C, 80% yield of N2 in the temperature range of 237–400 °C, unexceptionable H2O-resistance, high stability at 240 °C for 120 h. In situ DRIFTS reveals that the dissociation of (O)C-N bond is firstly involved in DMF oxidation, and then the stepwise and repeated dehydrogenation of -N(CH3)2 and the insertion reaction of surface lattice oxygen occurs. Meanwhile the formed -HCO is completely oxidized into CO2 and H2O by surface adsorbed oxygen species and the two adjacent -NH2 species combines into N2.

Synergistic photocatalytic nanozymes to promote contaminant removal and hydrogen production

Photocatalytic nanozymes, which combine light-induced redox reactions and enzyme-like catalysis, have emerged as a promising class of nanomaterials. This alliance offers tremendous potential for light-enhanced enzyme-like activity and expands the applications of nanozymes in energy and environmental fields. In this study, a photocatalytic nanozyme OVs-TiO2/Pd hybrid nanosheets (HNSs) with abundant oxygen vacancies (OVs) and controllable Pd components was prepared by a one-step solid-phase reduction method. Benefiting from the synergistic effect and the strong metal-support interaction, OVs-TiO2/Pd HNSs exhibit remarkable light-enhanced oxidase-like and hydrogenase-like activity, they efficiently catalyze the degradation of antibiotics and the production of hydrogen, respectively. Electron spin resonance and transient photovoltage techniques elucidated that the enhanced enzyme-like activities are attributed to the increased generation of charge carriers and reactive oxygen species. This study builds a bridge between photocatalysis and enzyme-like catalysis, opening up a new avenue to explore the multiple functional nanomaterials for a myriad of applications.

Photocatalytic ammonia synthesis from nitrate reduction on nickel single-atom decorated on defective tungsten oxide

Photocatalytic reduction of waste nitrate (NO3-) into value-added ammonia (NH3) under ambient conditions has enormous advantages over the Haber-Bosch process. However, weak adsorption capacity and low efficiency of photocatalysts limit its large-scale application. Here, Ni single-atom (SA) on defective WO3 (Ni/HxWO3−y) hybrids with abundant oxygen vacancies (OVs) are synthesized by a facile H-spillover process, which exhibits a high NH3 rate of 10.5 mmol gcat-1 h-1 and 98.26 % NH3 selectivity. In situ characterizations and theoretical calculations demonstrate the activity mainly derives from the synergetic effect of OVs and Ni SAs. That is, (1) photogenerated electrons and adsorbed NO3- transfer from OVs to Ni SAs; (2) the strong hybridizations of Ni 3d - O 2p orbitals of NO3- accelerate electron transfer from Ni SAs to NO3-; (3) Ni SAs effectively reduce the free energy of the rate-limiting step (NO2* → NO*) of HxWO3−y. In simulated wastewater, the durable performance of Ni/HxWO3−y hybrids proves great potential in industrial applications.