Catalytic Activity Of Metal Oxides Research Articles

A ZnO-002/amorphous Bi2WO6 heterojunction with enhanced electron-hole separation for high-performance Cr(VI) photoreduction

The difference in bandgap structure results in better charge separation performance of crystalline/amorphous heterojunctions compared to a single component. Considering that the catalytic activity of metal oxides is often accompanied by differences in facets, it has become an interesting topic to further improve the charge separation performance of such heterojunctions by adjusting the facets at the material contact interface. This article synthesized three novels ZnO/amorphous Bi2WO6 heterojunctions with specific facets (ZnO-101/aBi2WO6, ZnO-100/aBi2WO6 and ZnO-002/aBi2WO6) by adding ZnO with different facets to bismuth tungstate precursors through hydrothermal methods. Photoelectric testing shows that compared to a single component, all three heterojunctions display efficient carrier separation characteristics. Among them, the ZnO/aBi2WO6 heterojunction with the 002 facet exhibits more excellent performance, such as photocatalytic reduction of 150 mg·L−1 Cr(VI) without hole scavenger. The system spectral and energy spectrum characterization shows that the matched band structure induces a strong built-in electric field, which accelerates the separation of bulk carriers. And meanwhile, many oxygen vacancies, high specific surface area, low interface resistance and high concentration of carriers also provide help for the treatment of pollutants. In addition, 94.49 % of the photocatalytic activity was retained after 5 cycles, which proved the excellent photo cycling stability of the heterojunction.

Catalytic activity of metal oxides supported on graphene oxide in oxidative desulfurization and denitrogenation

In this work, the effect of different parameters on catalyst efficiency in the catalytic oxidative desulfurization (ODS) and denitrogenation (ODN) process is studied. A series of samples with different metal compounds, including Ni, Cu, Co, CoNi, CoCu, and CuNi on a reduced graphene oxide (GO) were prepared by an impregnation method. The synthesized samples were carefully characterized by Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, and X‐ray powder diffraction (XRD) techniques. The potential of this methodology was illustrated by the oxidation of 84.11% carbazole (CBZ) and 88.36% dibenzothiophene (DBT) in model fuel containing 500 ppmw sulfur and nitrogen. The effect of DBT and CBZ initial concentration and oxidant type on the oxidation process was investigated. The initial concentration of 250 ppmw for DBT and 100 ppmw for CBZ showed more efficiency than other initial concentrations (1,000, 750, 500, 250 ppmw) for DBT and (500, 400, 250, 100 ppmw) for CBZ, and NaClO as an oxidant showed higher performance than H2O2, formic acid, and oxygen. The results indicated that the Co‐Cu/rGO catalyst shows higher activity than other prepared catalysts in the oxidation of DBT and CBZ. Moreover, the catalyst could be regenerated three times with no discernible decrease in its catalytic activity. Lastly, the catalytic oxidation of CBZ and DBT was the proposed reaction mechanism.

Catalytic Conversion of Oil in Model and Natural Reservoir Rocks

The catalytic activity of metal oxides in the processes of low- and high-temperature oxidation (LTO and HTO, respectively) of oil was studied on model systems consisting of oil-saturated quartz sand with additives of Al2O3, Cr2O3 and MgO using thermal analysis methods. The used additives were shown to shift the LTO and HTO processes to the low-temperature region. The catalytic activity of a natural reservoir carbonate rock without and with water was studied. This study established that at room temperature in dry carbonate rock, the oil components undergo dealkylation and polycondensation of aromatic fragments for a week. In the presence of water, the polycondensation processes are suppressed, and the cracking of resin and asphaltene occurs. The cracking reactions lead to a decrease in the content of heteroatoms in resins and asphaltenes.

Remarkable assist of sulfate ion on solvent-free preparation of highly oxygen vacancy-rich MnO2 for enhancing peroxymonosulfate mediated advanced oxidation processes

Oxygen vacancy (VO) strongly influences the catalytic activity of metal oxides. However, Vo engineering usually requires solvent- and/or post-thermal processes. Here, we developed sulfate ion (SO42-)-assisted mechanochemical preparation of VO-rich MnO2 from ball milling of only KMnO4 and Mn2+ inorganic precursors. The catalytic activity of as-prepared MnO2 depended on the Mn2+ precursors in an increasing order of Mn(NO3) < MnCO3 < MnCl2 < MnSO4, and the addition of Na2SO4 or K2SO4 during the preparation process significantly increased the catalytic activity of MnO2, indicating the SO42−-assist. MnO2 prepared from MnSO4 efficiently activated peroxymonosulfate (PMS) to degrade organic pollutants such as ofloxacin, norfloxacin, and sulfamethoxazole with 2.3–44 times larger rate constants than previously reported MnO2. Extensive characterizations suggest that SO42− increases the formation of one-electron-trapped VO (VO•) and surface Mn(III)–OH on/in MnO2 and the catalytic activity of MnO2 positively correlates with the amount of VO•, because VO• improves PMS adsorption and Mn4+/Mn3+ redox cycle and oxygen mobility in MnO2 for the generation of singlet oxygen.

Revealing the correlation between adsorption energy and activation energy to predict the catalytic activity of metal oxides for HMX using DFT

Traditional selection of combustion catalysis is time-consuming and labor-intensive. Theoretical calculation is expected to resolve this problem. The adsorption energy of HMX and O atoms on 13 metal oxides was calculated using DMol3, since HMX and O are key substances in decomposition process. And the relationship between the adsorption energy of HMX, O on metal oxides (TiO2, Al2O3, PbO, CuO, Fe2O3, Co3O4, Bi2O3, NiO) and experimental T30 values (time required for the decomposition depth of HMX to reach 30%) was depicted as volcano plot. Thus, the T30 values of other metal oxides was predicted based on their adsorption energy on volcano plot and validated by previous experimental data. Further, the adsorption energy of HMX on ZrO2 and MnO2 was predicted based on the linear relationship between surface energy and adsorption energy, and T30 values were estimated based on volcano plot. The apparent activation energy data of HMX/MgO, HMX/SnO2, HMX/ZrO2, and HMX/MnO2 obtained from DSC experiments are basically consistent with our predicted T30 values, indicating that it is feasible to predict the catalytic activity based on the adsorption calculation, and it is expected that these simple structural properties can predict adsorption energy to reduce the large quantities of computation and experiment cost.

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In2O3 Particles.

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO2, SnO2, ZnO), and the type of conductivity of metal oxides (Co3O4, ZrO2) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO2-In2O3 on the structure of the resulting composites, as well as their conductive and sensor properties.

Utilization Waste Materials to Synthesize Nano Al2O3-CaO Photocatalyst using Infused Red Guava Leaves (Psidium Guajava L.)

Diazinon is a very toxic pesticide for animals and humans that is widely used in the agricultural sector, so this pollutant needs to be reduced or eliminated in the environment through photodegradation using photocatalysts derived from metal oxides. The catalytic activity of metal oxides is enhanced by adding a support material and increasing the surface area by reducing the particle size to nano size. In this study, kaolin as a source of Al2O3 and golden snail shells as a source of CaO which used to synthesize Al2O3-CaO nanoparticles (NPs) with a simple and environmentally friendly method using plant infusions. Synthesis of Al2O3-CaO NPs using infused red guava leaves (Psidium guajava L.) had been done by utilized the secondary metabolites as reducing agents and stabilizers in the nanoparticle synthesis. FTIR analysis confirmed the presence of alumina (Al-O) groups at wave numbers 850 – 650 cm-1 and CaO at 3642 cm-1. XRD analysis showed NPs Al2O3-CaO had cubic with the crystal size of 14.59 nm. The morphology of Al2O3-CaO NPs showed in the SEM pictures were agglomerated. Al2O3-CaO NPs degraded diazinon by 75% within 180 minutes under UV radiation. Thus, this research not only reduce waste material, but also reduces water pollutant.

Electrocatalytic Nitrate Reduction to Ammonia By Oxide-Derived Copper with Stacking Faults

The significant change of nitrogen cycle as a result of growing production and industrial use of nitrogen fertilizers has led to great environmental concern. The nitrate (NO3 -) in groundwater and industrial wastewater pose a serious threat to the nitrogen cycle and human health, which creates a need for efficient methods that can convert nitrate species. Although many techniques such as biological denitrification, ion exchange, reverse osmosis, and electrodialysis have been developed for NO3 --rich water remediation, electrocatalytic nitrate reduction reaction (NO3RR) is a promising technology that utilize electricity from renewable solar/wind energies to selectively reduce NO3 - to nitrogen (N2) or ammonia (NH3). Of note that NH3 is a fertilizer source and is also considered as a green hydrogen-rich fuels. Therefore, converting NO3 - in wastewater to recyclable NH3 is attractive with regard to environmental protection and energy saving.Metal oxide catalysts with well-controlled shape and size are currently developed to explore catalytic performance trends and intrinsic mechanism for the NO3RR. For example, Co3O4-based nanoparticles and nanosheet array exhibit improved performance because of the optimized exposed surface and size distribution. TiO2 nanotube arrays with anatase structure displayed better electrocatalytic activity than those with rutile structure. These findings have demonstrated that metal oxide catalysts with subtle composition and crystal structure play an important role in enhanced performance for the NO3RR. However, the redox potential for metal oxide reduction is more positive than the potential required for the NO3RR, so metal oxides can be further reduced to metal state under NO3RR.During the reduction process, the loss of structural oxygen ions in metal oxide catalyst would lead to its nonstoichiometry. Accordingly, the electrochemical reduction conditions may drive the generation of defects to accommodate the nonstoichiometry. Therefore, we hypothesized that the substantial structural perturbations such as dislocations could induce lattice strains in the defect region. Such lattice strains will modulate the local surface electronic structure of the catalysts, tuning the interaction between the reaction species and catalyst surface. As a result, the catalytic activity of metal oxides could be optimized.In this study, we selected Cu-based oxide electrodes to fully investigate the structural change and its effects on catalytic performance towards NO3RR. We found that Cu oxide catalysts have a distinct structural change during the NO3RR. The Cu oxide catalysts were reduced to metallic Cu under the negative potential of NO3RR, which serves as the actual active species. More importantly, we found that abundant stacking faults were formed on the oxide-derived Cu surfaces due to the applied negative potential during the NO3RR or the electroreduction pretreatment. The in situ electrochemical reduction-generated stacking faults can be utilized to increase NO3 --N removal, NH4 +-N selectivity, and NH3 Faradaic efficiency up to 93, 94, and 80%, respectively. On the basis of theoretical and experimental investigations, it is concluded that the tensile strain resulting from the stacking faults facilitates NO3 - adsorption and suppresses hydrogen evolution reaction. This work not only helps explain the improved reactivity of related metal oxide for the NO3RR, but also provides a general strategy to develop active and stable electrocatalysts with rational designed surface structure. Figure 1

Oxygen Vacancy-Dependent Chemiluminescence: A Facile Approach for Quantifying Oxygen Defects in ZnO.

Defect engineering is an effective strategy to improve the catalytic activity of metal oxides, and quantitative characterization of surface defects is thus vital to the understanding and application of metal oxide catalysts. Herein, we found that ZnO nanoparticles with oxygen vacancy could trigger the luminol-H2O2 system to emit a strong chemiluminescence (CL), and the CL intensity was strongly dependent on the oxygen vacancy of the ZnO nanoparticles. The mechanism of this CL reaction was discussed by means of the electron-spin resonance spectrum, X-ray photoelectron spectrum (XPS), and CL spectrum. The oxygen vacancy-dependent CL was attributed to the ability of the oxygen vacancy to readily adsorb and further dissociate H2O2 into active •OH radicals. Taking advantage of this oxygen vacancy-dependent CL, we presented one method for quantifying the oxygen defects in ZnO. Compared with the current evaluation techniques (XPS and Raman spectroscopy), this CL method is rapid, low-cost, and easy to operate. This work introduces the CL technique into the field of material structure-property evaluation, and provides a new approach for exploring the defect function in ZnO defect engineering.

Mechanochemically tailoring oxygen vacancies of MnO2 for efficient degradation of tetrabromobisphenol A with peroxymonosulfate

Oxygen vacancy (VO) engineering can efficiently improve the catalytic activity of metal oxides. This work developed a solvent-free mechanochemical method to tailor VO levels on the surface of commercial MnO2 under ambient conditions. After a typical ball milling treatment at 350 rpm for 20 min, the obtained VO-rich MnO2 activated peroxymonosulfate (PMS) to completely degrade tetrabromobisphenol (TBBPA) with a pseudo-first-order rate constant of 0.21 min−1, being 22 times larger than that for non-milled MnO2. 18O-labeling tests confirmed that singlet oxygen was generated from both PMS and lattice oxygen of MnO2 as dominant active species for the TBBPA degradation. It was clarified that the catalytic activity of MnO2 depends on not only VO levels, but also the local environment of VO, i.e., VO-associated cations. The Mn4+/Mn3+ redox couple is more important than Mn3+/Mn2+, and VO improves the oxygen mobility in/on MnO2 and Mn4+/Mn3+ redox reactions for the activation of PMS.

Understanding the oxygen-evolution-reaction catalytic activity of metal oxides based on the intrinsic descriptors.

Metal oxides show great potential in catalyzing the oxygen evolution reaction (OER), which is taken as the bottleneck of many energy-conversion and -storage processes. However, it is still a major challenge to deeply understand the catalytic mechanism and to rapidly screen out novel metal-oxide catalysts. Herein, we find that the trend of adsorption energies of O-intermediates and the theoretical overpotentials on metal monoxides (MO), metal dioxides (MO2), and perovskite oxides (ABO3) can be determined using the descriptor ψ, which is related to the valence-electron numbers and the electronegativities of the active center. The underlying mechanism is that ψ reflects the p-band properties of superficial and adsorbed O atoms of metal oxides and thus can reveal the commonality and difference of adsorption and catalysis of the three types of metal oxides. Moreover, the ψ-determined relationships indicate the possibility of breaking the previously proposed thermodynamic limitation on the post-transition metal oxides and rationalizing the trend of experimental OER catalytic activity of metal oxide catalysts. With this easily accessible intrinsic descriptor ψ, we provide a convenient and feasible scheme for designing new candidates for OER catalysts.

Preparation of an electrochemical immunosensor based on a Cu/Cu2O-rGO@Au signal synergistic amplification strategy and efficient and sensitive detection of alpha-fetoprotein.

The effective amplification of the signal is the prerequisite for the ultrasensitive detection of electrochemical immunosensors. To quantitatively detect alpha-fetoprotein (AFP), we prepared a sandwich-type electrochemical immunosensor. Using a gold nanoparticles (Au NPs) modified glassy carbon electrode (GCE) as the sensing platform and Cu/Cu2O-rGO@Au as the signal label, differential pulse voltammetry (DPV) was used to achieve sensitive detection of AFP. We found that the nanomaterials can undergo electro-oxidation and electro-reduction reactions between Cu(I) and Cu(II) in a buffer solution of pH = 6.0. It is worth mentioning that the incorporation of metals into metal oxide substrates is a new strategy to combine the catalytic activity of metal oxides with the electrical conductivity of metals. Reduced graphene oxide (rGO), which is rich in oxygen-containing groups, can load more Cu/Cu2O and Au NPs and increase the conductivity. The modification of Au NPs makes them have better biocompatibility and conductivity. Under the best detection conditions, the prepared immunosensor realizes the specific and ultrasensitive detection of AFP. The detection range is 0.01-50 ng mL-1 and the limit of detection (LOD) was as low as 0.589 pg mL-1 (S/N = 3); meanwhile it also has good practical application ability. Therefore, this immunosensor provides an important means for the early screening and detection of AFP.

Phase Engineering of Metal Oxides for Enhanced Energy Application

A recent ongoing technological breakthrough in numerous fields including eco-friendly energy, electronics, transportation, defense, and security, etc. is immensely challenged by the inadequate capability of energy devices. Deliberate efforts in researches that could lead to obtaining reliable energy devices are being carried out applying diverse approaches. In this study, the structure of the materials has been considered and examine its impact on electrocatalysis and hence its green fuel production capability. The porous NiFe-oxide nanocubes (NCs) system is generated from a NiFe Prussian analog metal-organic framework. In 1M KOH, the nanocubes demonstrate overpotentials of 54 mV and 298 mV for HER and OER, respectively to deliver a current of 10 mA/cm2 whereas the spherical NiFe-oxide nanoparticles (NPs) of similar composition showed respective overpotentials of 187 mV and 258 mV for HER and OER. The incredible catalytic performance of NiFe-NCs is attributed to the exposure of active sites at the edges and vertices of NCs. Moreover, both the NPs and NCs showed interesting property changes after being sulfurized. Sulfurized nanocubes (NCs-S) demonstrated overpotentials of 177 mV and 241 mV whilst sulfurized nanoparticles (NPs-S) showed overpotentials of 152 mV and 216 mV for HER and OER, respectively. On top of that, the electrochemical measurements in 3M KOH showed the increase of the specific capacitances of NCs and NPs after sulfurization from 69 to 604 F/g and from 185 to 514F/g, respectively, at a current density of 1 A/g. Our study suggests that a facile sulfurization process could significantly improve catalytic activities of metal oxides.

Complete Formaldehyde Removal over 3D Structured Na1.1Mn4O8@Mn5O8 Biphasic‐Crystals

AbstractWith the increasing concerns on the formaldehyde (HCHO) hazard, the efficient oxidation of HCHO over affordable and harmless catalyst is of significant practical interest. Herein, the intermediate state of Mn5O8−Na1.1Mn4O8 (Na−Mn5O8) biphasic‐crystal catalyst, which features Na1.1Mn4O8‐nanosheet@ Mn5O8‐nanorod interconnected 3D structure, is successfully fabricated through the anaerobic calcination of manganite followed by alkali treatment. The resultant Na−Mn5O8 exhibits 100 % conversion of HCHO (150 ppm and 60000 h−1) and reliable stability (50 h) at 90 °C under demanding water‐free feed conditions, which is superior to that of the reference samples of Mn5O8, Na1.1Mn4O8, MnO2 and Na−MnO2. The experimental results demonstrate that the abundant structure defects (oxygen vacancies) on Na−Mn5O8, which may locate along the phase interfaces / shared‐edges of Mn5O8 nanorods and Na1.1Mn4O8 nanosheets, significantly enhance the active oxygen species and finally contribute to the high activity for HCHO oxidation. Furthermore, the 3D structure of Na−Mn5O8 favors mass transfer and fully exposing active sites for the HCHO adsorption and conversion. These findings reveal a way to enhance the catalytic activity of metal oxides via controlling the intermediate state of heteropical crystals.

Boosting Oxygen Evolution Reaction by Creating Both Metal Ion and Lattice-Oxygen Active Sites in a Complex Oxide.

Developing efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance to many chemical and energy transformation technologies. The diversity and flexibility of metal oxides offer numerous degrees of freedom for enhancing catalytic activity by tailoring their physicochemical properties, but the active site of current metal oxides for OER is still limited to either metal ions or lattice oxygen. Here, a new complex oxide with unique hexagonal structure consisting of one honeycomb-like network, Ba4 Sr4 (Co0.8 Fe0.2 )4 O15 (hex-BSCF), is reported, demonstrating ultrahigh OER activity because both the tetrahedral Co ions and the octahedral oxygen ions on the surface are active, as confirmed by combined X-ray absorption spectroscopy analysis and theoretical calculations. The bulk hex-BSCF material synthesized by the facile and scalable sol-gel method achieves 10 mA cm-2 at a low overpotential of only 340 mV (and small Tafel slope of 47 mV dec-1 ) in 0.1 m KOH, surpassing most metal oxides ever reported for OER, while maintaining excellent durability. This study opens up a new avenue to dramatically enhancing catalytic activity of metal oxides for other applications through rational design of structures with multiple active sites.

Amidation of fatty acid methyl ester using metal oxides and hydroxides as catalysts

Comparison of catalytic activity of metal oxides and hydroxides in amidation reaction between fatty acid methyl esters and 3-(dimethylamino)-1-propylamine was made for the first time. Influences of basicity, structure and solubility of catalysts on its catalytic activity were shown. It was detected, that catalysis of amidation of fatty acid methyl esters is homogenous. High activity of mixed oxides (Fe3O4 and Co3O4) was noted.

Density Functional Theory Calculations of Oxygen Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces

The surface oxygen vacancy formation energy (EOvac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine EOvac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence EOvac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O2, NO, CO, CO2, and H2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and EOvac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.

Impact of Strain-Induced Changes in Defect Chemistry on Catalytic Activity of Nd2NiO4+δ Electrodes.

It is well known that defect chemistry plays a vital role in determining the electronic structure, ionic conductivity, and catalytic activity of metal oxides, as demonstrated in perovskite-based oxides to achieve desired functionalities. In this work, we explored the possibility of tuning the defect chemistry and hydrogen oxidation reaction (HOR) activity of Nd2NiO4+δ model thin films by controlling the lattice strain. Highly textured Nd2NiO4+δ thin films with different strain states were prepared on (110)- and (100)-oriented single-crystal yttrium-stabilized zirconium (YSZ) substrates using pulsed laser deposition. Electrochemical impedance spectroscopy results indicated that the NNO(100) film on the YSZ(110) substrate with larger tensile strain in the a- b plane and compressive strain along the c axis exhibited higher HOR activity than the NNO(110) film on the YSZ(100) substrate at 500-600 °C. The enhancement in HOR activity is attributed to the strain-induced difference in the oxygen defect concentration, as confirmed by high-resolution X-ray diffraction analysis. We believe that the correlation among the strain state, defect chemistry, and catalytic properties is helpful for rational design of more efficient electrode materials.

Defect Engineering of Chalcogen-Tailored Oxygen Electrocatalysts for Rechargeable Quasi-Solid-State Zinc-Air Batteries.

A critical bottleneck limiting the performance of rechargeable zinc-air batteries lies in the inefficient bifunctional electrocatalysts for the oxygen reduction and evolution reactions at the air electrodes. Hybridizing transition-metal oxides with functional graphene materials has shown great advantages due to their catalytic synergism. However, both the mediocre catalytic activity of metal oxides and the restricted 2D mass/charge transfer of graphene render these hybrid catalysts inefficient. Here, an effective strategy combining anion substitution, defect engineering, and the dopant effect to address the above two critical issues is shown. This strategy is demonstrated on a hybrid catalyst consisting of sulfur-deficient cobalt oxysulfide single crystals and nitrogen-doped graphene nanomeshes (CoO0.87 S0.13 /GN). The defect chemistries of both oxygen-vacancy-rich, nonstoichiometric cobalt oxysulfides and edge-nitrogen-rich graphene nanomeshes lead to a remarkable improvement in electrocatalytic performance, where CoO0.87 S0.13 /GN exhibits strongly comparable catalytic activity to and much better stability than the best-known benchmark noble-metal catalysts. In application to quasi-solid-state zinc-air batteries, CoO0.87 S0.13 /GN as a freestanding catalyst assembly benefits from both structural integrity and enhanced charge transfer to achieve efficient and very stable cycling operation over 300 cycles with a low discharge-charge voltage gap of 0.77 V at 20 mA cm-2 under ambient conditions.

The effect of manganese vacancy in birnessite-type MnO2 on room-temperature oxidation of formaldehyde in air

Catalytic reaction active site tends to be the structural defects, such as edges, corners, ribs and other position that has low coordination number. Here, the potassium (K+) type birnessite (i.e. a layered-structure MnO2) was designed with different amounts of manganese vacancy (VMn) for catalytic oxidation of formaldehyde (HCHO). The content of VMn was determined by the ratio of Mn/O and coordination number of Mn–Mn edge-sharing structure. The VMn showed a dramatic promotion effect on the activity of birnessite for HCHO oxidation. The specific rate at 30°C over the birnessite with the highest content of VMn was highest (0.052μmol/m2min) under 40ppm of HCHO, 120,000mL/g h of GHSV and ∼80% of relative humidity. The presence of VMn induced unsaturated oxygen species and K+ locating nearby VMn sites for charge balance facilitated the formation of active oxygen species, accordingly the activity for HCHO oxidation was greatly improved. This finding reveals a way to enhance the catalytic activity of metal oxides via adjusting metal vacancies.