Birnessite-type MnO2 Research Articles

Degradation of P-Nitrobenzoic Acid and 4-Chlorobenzoic Acid by Catalytic Ozonation with Modified Birnessite-Type MnO2 as Catalyst

Degradation of P-Nitrobenzoic Acid and 4-Chlorobenzoic Acid by Catalytic Ozonation with Modified Birnessite-Type MnO2 as Catalyst

Protons intercalation induced hydrogen bond network in δ-MnO2 cathode for high-performance aqueous zinc-ion batteries

Birnessite-type MnO2 (δ-MnO2) exhibits great potential as a cathode material for aqueous zinc-ion batteries (AZIBs). However, the structural instability and sluggish reaction kinetics restrict its further application. Herein, a unique protons intercalation strategy was utilized to simultaneously modify the interlayer environment and transition metal layers of δ-MnO2. The intercalated protons directly form strong O H bonds with the adjacent oxygens, while the increased H2O molecules also establish a hydrogen bond network (O H···O) between H2O molecules or bond with adjacent oxygens. Based on the Grotthuss mechanism, these bondings ultimately enhance the stability of layered structures and facilitate the rapid diffusion of protons. Moreover, the introduction of protons induces numerous oxygen vacancies, reduces steric hindrance, and accelerates ion transport kinetics. Consequently, the protons intercalated δ-MnO2 (H-MnO2-x) demonstrates exceptional specific capacity of 401.7 mAh/g at 0.1 A/g and a fast-charging performance over 1000 cycles. Density functional theory analysis confirms the improved electronic conductivity and reduced diffusion energy barrier. Most importantly, electrochemical quartz crystal microbalance tests combining with ex-situ characterizations verify the inhibitory effect of the interlayer proton environment on basic zinc sulfate formation. Protons intercalation behavior provides a promising avenue for the development of MnO2 as well as other cathodes in AZIBs.

Efficient fluoride removal in hybrid capacitive deionization enabled by Ce-Zn-MOF-derived CeO2@C and birnessite electrodes

Fluorine pollution has become a public health issue of global concern. Capacitive deionization (CDI) presents the benefits of simple operation, high energy efficiency, and good sustainability. The development of high adsorption performance, economical and environmentally friendly defluorination electrodes is the key direction of capacitive deionization. Here, a spherical metal–organic framework (MOF) Ce/Zn-BTC was prepared by solvothermal method utilizing benzene-tricarboxylic (BTC) acid as solvent, and then it was transformed into CeO2@C composites through pyrolysis. The spherical structure of the original MOFs is preserved by CeO2@C, leading to significant enhancements in specific surface area (275.48 m2/g), pore volume (0.3359 cm3/g), and electrochemical performance. In this work, the anode material CeO2@C was employed for the first time, while birnessite-type MnO2 (δ-MnO2) was utilized as a cathode material for the fabrication of a hybrid CDI (HCDI) device for the treatment of fluorinated wastewater. The CeO2@C/δ-MnO2 cell shows excellent fluoride removal performance with a removal capacity of 22.03 mg/g for 50 mg/L fluoride solutions under a 1.2 V applied voltage, which is better than most carbon-based materials. Importantly, the CeO2@C/δ-MnO2 cell has favorable fluoride selectivity and regeneration performance (>75 %) even after undergoing ten cycles. Fluoride is mainly removed by intercalation into the carbon skeleton, coordination with Ce, and electrostatic interaction. This study shows that the CeO2@C/δ-MnO2 cell has excellent fluoride removal performance and practical application prospects.

Nonradical-dominated pathway toward selective catalytic ozonation of NH4+-N to N2 in drinking water over birnessite

Ammonia nitrogen (NH4+-N), which exists in the dominant form of ammonium ion (NH4+) under the pH of 6.5–8.5, is one of the regular indexes and the most important pollutants in drinking water. The selective conversion of NH4+-N into harmless substances is urgently needed and also a great challenge. Herein we propose a new NH4+-N conversion pathway based on a catalytic ozonation process with birnessite-type MnO2 (δ-MnO2) catalysts. The δ-MnO2 exhibits a superior performance for NH4+-N (1.0 mg/L) removal in adsorption (8.26 %) and oxidation (44.6 %) as well as up to 95.2 % of N2 selectivity, surpassing almost all the reported O3-based catalysts. Unlike the traditional radical oxidation, a singlet oxygen (1O2)-dominated nonradical oxidation pathway is confirmed for the efficiently selective conversion of NH4+-N to N2 through the successive dehydrogenation, leading to a 15.0-fold enhancement in NH4+-N oxidation rate compared with ozone oxidation. The Mn(III)/Mn(IV) redox sites and surface lattice oxygen in δ-MnO2 act as the active sites promoting the decomposition of O3 into •O2− and then 1O2 via electrons transfer. In application, δ-MnO2 catalytic ozonation effectively removes NH4+-N in real drinking water and presents excellent stability. This work finds a nonradical reaction mechanism in catalytic ozonation for NH4+-N selective conversion to N2, and solidly solves the problem of low-concentration NH4+-N removal from drinking water under the limited pH of 6.5–8.5 condition.

Birnessite-Type MnO2 Modified Sustainable Biomass Fiber toward Adsorption Removal Heavy Metal Ion from Actual River Aquatic Environment.

In this work, a novel birnessite-type MnO2 modified corn husk sustainable biomass fiber (MnO2@CHF) adsorbent was fabricated for efficient cadmium (Cd) removal from aquatic environments. MnO2@CHF was designed from KMnO4 hydrothermally treated with corn husk fibers. Various characterization revealed that MnO2@CHF possessed the hierarchical structure nanosheets, large specific surface area, and multiple oxygen-containing functional groups. Batch adsorption experimental results indicated that the highest Cd (II) removal rate could be obtained at the optimal conditions of adsorbent amount of 0.200 g/L, adsorption time of 600 min, pH 6.00, and temperature of 40.0 °C. Adsorption isotherm and kinetics results showed that Cd (II) adsorption behavior on MnO2@CHF was a monolayer adsorption process and dominated by chemisorption and intraparticle diffusion. The optimum adsorption capacity (Langmuir model) of Cd (II) on MnO2@CHF was 23.0 mg/g, which was higher than those of other reported common biomass adsorbent materials. Further investigation indicated that the adsorption of Cd (II) on MnO2@CHF involved mainly ion exchange, surface complexation, redox reaction, and electrostatic attraction. Moreover, the maximum Cd (II) removal rate on MnO2@CHF from natural river samples (Xicheng Canal) could reach 59.2% during the first cycle test. This study showed that MnO2@CHF was an ideal candidate in Cd (II) practical application treatment, providing references for resource utilization of agricultural wastes for heavy metal removal.

Regulation of surface acidic sites on birnessite-type MnO2 and its function in the adsorption of gaseous ammonia

Ammonia (NH3) is not only a characteristic malodorous contaminant, but also one of the important precursors in the formation of haze. In engineering practice, the most widely used technology for NH3 purification is adsorption, and the development of adsorbent with excellent NH3 adsorption capacity is the key to adsorption method. Herein, the surface acidic sites of layered birnessite-type MnO2 were regulated for the adsorption of NH3. Results presented that the adsorption capacity of birnessite-type MnO2 reinforced by surface acidic sites could reach 36.1 mg/g, which significantly superior to pristine MnO2 and other commercial carbon materials. In addition, the effects of space velocity, NH3 concentration, adsorption temperature and relative humidity on its adsorption performance were also studied. It was found that the effect of space velocity and relative humidity had no significant effect on the equilibrium NH3 adsorption capacity; while the equilibrium adsorption capacity showed an increasing trend with the rise of NH3 concentration and the decrease of adsorption temperature. Furthermore, the function of surface acidic sites, especially Lewis and Brønsted acidic sites, in the adsorption of birnessite-type MnO2 for NH3 was further revealed. On the one hand, the acidic site strengthening method of acid impregnation can significantly increase the specific surface area of birnessite-type MnO2, which is beneficial for the physical adsorption of NH3. Importantly, this acidic site strengthening method significantly enhances the number and intensity of surface acidic sites of birnessite-type MnO2, especially the Brønsted acidic sites, which greatly promoted the adsorption of alkaline gas NH3. Finally, the cyclic thermal regeneration performance at low temperatures was further studied. This work reports a strategy to improve NH3 adsorption performance by enhancing acidic sites, and further reveals the functional role of surface acidic sites in NH3 adsorption.

Ammonium ion intercalation and oxygen-rich vacancies in birnessite-type MnO2 for supercapacitors and oxygen evolution applications

Defect engineering is an effective strategy to improve the electrochemical and electrocatalytic properties of transition metal oxide-based electrode materials.

Promoting cycle stability and rate performance of birnessite-type MnO2 cathode via cupper and bismuth dual ions pre-intercalation for aqueous zinc-ion batteries

Birnessite-type MnO2, as a promising and attractive cathode material for rechargeable aqueous zinc-ion batteries, is plagued by grievously poor cycling stability and rate performance, mainly attributed to structural collapse of MnO2 and slow Zn2+ diffusion kinetics. Herein, the Cu/Bi dual ions pre-intercalated birnessite-type MnO2 was fabricated by one-step hydrothermal method. It is validated by theoretical calculation in conjunction with experimentation that the Cu/Bi ions tends to occupy L1 sites, which not only can accelerate Zn2+ diffusion kinetics owing to the low the Zn2+ diffusion energy barrier, but also can stabilize the structure of MnO2 host due to the formation of chemical bonds between the pre-intercalated Cu/Bi ions and oxygen atoms. Consequently, the CBMO cathode displays a high discharge capacity of 412.3 mAh/g at 0.1 A/g and distinguished cycling stability at 3 A/g after 1000 cycles with only approximately 0.0042 % capacity fading per cycle, which will be a strong competitive cathode material for developing stable and high-performance rechargeable aqueous zinc-ion batteries.

Tailoring Oxygen Vacancies and Active Surface Oxygen Species in Copper-Doped MnO2 Catalysts for Total Catalytic Oxidation of VOCs

Catalytic oxidation has been considered an essential route to tackle volatile organic compounds (VOCs)-driven pollution. To this point, surface engineering has emerged as a robust pathway to promote the efficiency of MnO2-based materials toward VOC oxidation. However, regulating such surface properties has been a critical challenge. This investigation attempts to tailor surface oxygen vacancies and active surface oxygen for the total catalytic oxidation of various VOCs (e.g., formaldehyde, isopropanol, and toluene) via doping copper into cryptomelane and birnessite-type MnO2 catalysts. The catalysts are synthesized by a novel facile successive redox precipitation method between KMnO4 and an ethanol solution containing copper nitrate precursors, followed by annealing. It turns out that the low amount of Cu dopants, corresponding to the copper-to-manganese ratio of 0.17 (RCu/Mn = 0.17), generates a tunnel-structured cryptomelane-type MnO2 with strong bulk oxygen mobility. Such a crystalline structure exhibits the best catalytic performance for the total catalytic oxidation of toluene. The higher copper loading (RCu/Mn = 0.27–0.34) drives the formation of Cu-doped layered birnessite-type MnO2 materials containing rich oxygen vacancies and high active surface oxygen species. Those catalysts promote the oxidation of isopropanol and formaldehyde, respectively. To this end, oxygen vacancies and surface oxygen species crucially steer the molecular oxygen activation and interactions toward adsorbed oxygen species, significantly promoting the total oxidation of isopropanol and formaldehyde, respectively. The explored finding could disclose an outstanding platform toward highly selective and efficient oxidation of VOCs.

Ultrafast synthesis of K cations inserted birnessite-type MnO2 electrode in ethanolamine based deep eutectic solvents with improved supercapacitor performance

Specific capacitance of energy storage devices depends on the electrode materials and various manganese oxides have recently been developed and attracted much attention due to their superior electrochemical performance with high capacitance, energy density, and cyclic stability. Herein, K cations inserted birnessite-type MnO2 was ultrafast synthesized by a facile room temperature wetchemical method under ethanolamine based deep eutectic solvents (DESs), where monoethanolamine (MEA), diethanolamine, and triethanolamine were used as hydrogen bond donor (HBD) and choline chloride (ChCl) was acted as hydrogen bond acceptor. The results indicate that K+ can be pre-inserted into the layers of birnessite-type MnO2 during the preparation process by the addition of ethanolamine based DESs. The morphology, crystallinity, and porosity of manganese oxides can be effectively adjusted by changed types of HBD in the DESs. The mesoporous granular K+ pre-inserted birnessite-type MnO2 prepared in [ChCl:2MEA] (MnOx-CM) with a high specific surface area of 220 m2/g and electrical conductivity exhibits the best electrochemical performance with high specific capacitance of 290 F/g at the current density of 0.1 A/g. The pre-inserted K+ ions participating in the redox process of birnessite-type MnO2 can efficiently improve the electrochemical energy storage and cycling stability. Thus, the MnOx-CM can still maintain 92.5% capacity retention after 8000 cycles.

Acidity and metal complexation of edge surface of birnessite-type MnO2: Insight from first principles simulations.

Birnessite-type MnO2 plays key roles in scavenging trace elements in numerous natural environments and has also been regarded as a promising energy storage material. The interfacial properties of birnessite are highly pH-dependent due to the presence of various amphoteric groups on its edges, and, therefore, the acidity constants (pKa) of these groups are vital to the understanding of its electrochemical and environmental performances. However, an accurate acidity dataset for birnessite is absent yet. In this study, we employed first-principles molecular dynamics simulations and the vertical energy gap method to calculate the pKas of groups on the birnessite (010) edge. The interfacial hydration structure was characterized with a focus on the hydrogen bonding network. The obtained pKas suggest that MnOH2 is active while Mn2OH remains inert in a common pH range. Based on these results, the incorporation of transition metals on the edge surface was investigated by taking Ni2+ and Zn2+ as the model cations. The energy changes associated with the incorporation process of Ni2+ from the outer-sphere state indicate that incorporation on the edge surface is more feasible than that on the basal surface presumed in previous studies. Overall, the results obtained provide an atomic-scale insight into the acid-base chemistry of birnessite and form a physical basis for understanding the interfacial processes of birnessite.

Mn-vacancy birnessite for photo-assisted elimination of formaldehyde at ambient condition

Visible light-assisted catalysis has recently attracted considerable attention because it is efficient, cost effective, and does not cause indoor air pollution. Several birnessite-type MnO2 catalysts with different numbers of manganese vacancies (MVs) were synthesized in this study and used for photo-assisted catalytic oxidation of HCHO. Under visible light irradiation, MVs act as trapping centers to accelerate electrons transport and produce abundant reactive radicals to boost the activation of molecular oxygen, thereby improving the catalytic HCHO oxidation. The birnessite with the highest number of MVs exhibits remarkable oxidation activity with 80 ppm of HCHO (42% HCHO conversion was attained at ambient temperature) and a corresponding gas hourly space velocity (GHSV) of 60 L/(g·h) in a dynamic experiment. Moreover, it mineralizes 80 ppm of HCHO within 160 min in a static experiment, whereas it only takes 90 min under the same conditions with the visible light irradiation. The activity factor of birnessite with the highest MV content under visible light irradiation is 2.2 times that observed under dark conditions. Overall, this study elucidates the photothermal catalytic oxidation of HCHO, and concludes that the birnessite comprising MVs is a promising material for air purification applications.

Electrochemical behavior of MnO2/MWCNT nanocomposites for electrode material in supercapacitor

This study presents the findings of MnO2 tailoring in MWCNT for supercapacitor applications. Using a solvothermal method, we developed the MnO2/MWCNT nanocomposites with high energy storage capacity. The XRD peaks revealed the hexagonal structure of graphite and the tetragonal structure of birnessite type MnO2. TEM revealed that the MWCNT sidewalls were decorated with a huge number of high purity manganese nanoparticles. According to CV studies, the composite electrode's specific capacitance exceeds 314F/g. As per the researchers, the tailored MnO2/MWCNT nanocomposites should promote the best electrode material for supercapacitor applications.

Enhancement in catalytic performance of birnessite-type MnO2-supported Pd nanoparticles by the promotional role of reduced graphene oxide for toluene oxidation

We designed and prepared δ-MnO2-supported reduced graphene oxide-promoted Pd nanoparticles (xPd–yrGO/δ-MnO2). Such a catalytic material is promising in the practical application for VOCs removal.

Importance of water content in birnessite-type MnO2 catalysts for HCHO oxidation: Mechanistic details and DFT analysis

Water is featured in an indispensable role during the process of catalytic oxidation of HCHO. In this work, a rich water-containing birnessite-type MnO2 was synthesized, and its water content was adjusted through calcination. Phase structure and texture properties of the prepared birnessite were characterized. It was revealed that three types of water (namely absorbed water, molecular water, and structural hydroxyl) existed in birnessite. With the loss of water content, the interlayer distance of samples had decreased which changed the structure of birnessite to cryptomelane. This converted the morphology from an initial layered shape to a rod-like shape. Besides, the underlying mechanism for this effect on HCHO catalytic oxidation was elucidated. Results indicated that hydroxyl groups could slowly and sequentially oxidize HCHO to DOM, formate, and carbonate species. The hydroxyl groups also promoted the formation of oxygen vacancy which could activate O2 to O− 2 and O−. The hydroxyl groups which were consumed had originally been supplied by the reaction between O- 2, O−, and H2O (absorbed and interlayer water in birnessite) which was then replenished from air stream. Clearly, water is favorable to the catalytic reaction. It is the main reason why birnessite can continuously decompose HCHO.

Acid treated Ce modified birnessite–type MnO2 for ozone decomposition at low temperature: Effect of nitrogen containing co-pollutants and water

In this study, HNO3 treated Ce modified birnessite–type MnO2 (CexMn-AT; x = 0.01,0.1,0.2,0.5) have been designed for decomposition of ozone at low temperature (20–40 °C) in the absence or presence of nitrogen containing co-pollutants and water. The best catalyst Ce0.01Mn-AT exhibits stable ozone conversion of 94 % in nearly dry air (300 ppm of ozone, RH = 0.7 %, GHSV = 1200 L/(g.h), 20 °C) in the presence of N2O5/HNO3 pollutants. However, the ozone conversion drops to 64 % for the undoped catalyst showing the beneficial role of cerium. Additionally, the Ce0.1Mn-AT catalyst shows a stable ozone conversion of 91 % after 5 h on stream in moist air (RH = 30 %, 30 °C) in the same operating conditions as before. The high tolerance of the best acid-treated catalysts to co-pollutants and water can be explained by the high density of acid sites and oxygen vacancies which facilitate the adsorption and decomposition of ozone and allow to minimize the amount of nitrogen containing adspecies which can affect the catalytic performances for ozone decomposition.

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

Birnessite-type short rod-like MnO2 achieving propane low-temperature destruction: Benign synthesis strategy and reaction mechanism determination

Developing economical and robust noble metal-free materials for obstinate light alkane low-temperature decomposition is of great significance. Here, birnessite-type short rod-like MnO2 was firstly prepared by facile mixing KMnO4 and ascorbic acid under ambient conditions and employed in propane catalytic decomposition. Experimental results revealed that abundant oxygen vacancies and high valent Mn4+ species, superior reducibility, and high surface oxygen mobility guarantee the remarkable low-temperature activity of MnO2-SR, over which 90% of propane can be oxidized (T90) at temperature as low as 225 °C, achieving a temperature reduction over 70 °C compared with that of δ-MnO2 (T90 = 300 °C) and α-MnO2 (T90 = 355 °C). In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the dissociation and activation of propane molecules is the decisive step in propane oxidation. Gaseous propane is slowly oxidized by adsorbed oxygen directly to the final mineralization products at low temperature region (<200 °C); at high temperature region (>200 °C) however, propane molecules are firstly dissociated and activated before oxidized to carbonate intermediate products over active oxygen, and then eventually oxidized to carbon dioxide and water.

Atomically Dispersed Y or La on Birnessite-Type MnO2 for the Catalytic Decomposition of Low-Concentration Toluene at Room Temperature.

Room-temperature catalytic decomposition of low-concentration volatile organic compounds (VOCs) in indoor air is an exciting dream to solve their pollution. Herein, two kinds of rare-earth elements (Y and La) were separately doped into birnessite-type MnO2 nanosheets in the form of single atoms by the hydrothermal method. As-synthesized La/MnO2 achieved 100% removal of 10 ppm toluene at 40 °C under the gas hourly space velocity of 60 L g-1 h-1, which was even somewhat better than the single Pt atom-doped MnO2. In addition, La/MnO2 showed the good durability at room temperature for 0.5 ppm toluene removal under the GHSV of 300 L g-1 h-1 and could be effectively regenerated at 105 °C. GC/FID, online-MS and TD-GC/MS analysis demonstrated that only ignorable trace benzene (∼3.4 ppb, < one thousandth of inlet toluene) was generated in the gas phase during catalytic decomposition of 10 ppm toluene at room temperature. This research sheds light on the development of low cost and high activity catalysts for low-concentration VOC oxidation at room temperature.

Activated carbon fiber yarns with birnessite-type MnO2 and oxygen-functional groups for high-performance flexible asymmetric supercapacitors

Carbon fiber yarn (CFY) is deemed to be an ideal fiber flexible substrate because of its excellent mechanical flexibility, conductivity, and low-cost. In this study, positive electrode was prepared by hydrothermal process to form a birnessite-type MnO2 interconnected 3D nanostructure loading on the carbon fiber yarn (MnO2@CFY). Using an acid-etching process, the oxygen-containing functional groups successfully introduce to the surface of carbon fiber yarn (OCFY) as the negative electrode. The asymmetric all-solid-state flexible fiber-shaped supercapacitor (AFFSC) based on as-prepared MnO2@CFY and OCFY delivers an excellent volumetric energy density of 11.05 mWh cm−3 at a volumetric power density of 100.32 mW cm−3, maintaining 95.33% capacitance retention after 5000 bending cycles.