Commercial MnO2 Research Articles

A general molten salt method to conduct doping engineering for high-performance LiMn2O4 cathode

The doping strategy is considered as an effective method to enhance the electrochemical performances of LiMn2O4 (LMO). There is little report on the simultaneous preparation and doping of LMO by molten salt method. Herein, a ternary molten salt of KCl@LiCl@MCl2 (M = Ni, Cu, and Co) is proposed to convert commercial MnO2 to M-doped LMO, the successful preparation is proved by various characterizations. More importantly, the doping engineering enhances the charge transfer and storage of LMO, and ex-situ XRD and XPS prove the improved structure stability of LMO in the cycling test. Therefore, Ni-doped LMO offers a high reversible capacity of 108.6 mA h g−1 at 0.05 A g−1 and a long cyclic life with 87.4 mA h g−1 after 800 cycles at 0.2 A g−1. This work offers a new idea for implementing doping strategy.

Catalytic selectivity in activating peroxymonocarbonate with a commercial MnO2 catalyst for water remediation

An in-situ formed peroxymonocarbonate (HCO4-) oxidation system from an equilibrium reaction of H2O2 and HCO3– was established for eliminating organic pollutants in water. With H2O2 as a co-existing oxidant in the system, a commercial available MnO2 was able to proceed selective catalytic activation of HCO4- to generate reactive oxygen species (ROS), such as ·OH and CO3·-. The MnO2 catalyst showed excellent catalytic ability, structural stability and recyclability in the HCO4--based oxidation system for removing tetracycline. The degradation rate of tetracycline reached 86 % and the catalyst could be used for at least 5 times with only 0.1 ppm of Mn leached in water. The kinetic study indicated that HCO4- was more related to the degradation of tetracycline and generated ·OH at the yield of 40 % was primarily from HCO4- activation rather than H2O2 activation. The evaluation of ROS and quenching experiments suggested that CO3·- was most responsible for tetracycline degradation. The catalyst characterization and reaction mechanism indicated that low-valent Mn species were the active sites for HCO4- activation. Finally, in-situ formation of HCO4- derived from CO2 in Na2CO3 solution with H2O2 was preliminarily explored, presenting a MnO2-catalzyed CO2-derived HCO4--based oxidation system for pollutant control. This study shows that a cheap and commercial available MnO2 can be an efficient, facile and selective catalyst for in-situ formed HCO4--based advanced oxidation processes.

Phase evolution of nanocrystalline Mn-based oxides screened under different calcination temperatures using different precursors for proficient application in near infrared pigmentation

We examined how different calcination temperatures and precursors affect the formation of Mn-based oxides. The formation of these oxides was influenced by both the temperature (400–––1000 °C) and the type of precursors used (MnCl2·4H2O, MnCO3, MnO2, and KMnO4). When MnCl2·4H2O was calcined at 800 and 1000 °C/3h, we obtained pure tetragonal Mn3O4 phase materials. Calcining MnCO3 at 600 and 1000 °C resulted in cubic Mn2O3 and tetragonal Mn3O4 phase materials, respectively. Heating commercial MnO2 powder at 600 and 800 °C transformed it into cubic Mn2O3 phase materials. At 400 °C, the tetragonal MnO2 phase remained, but at 1000 °C, mixed Mn3O4 and Mn2O3 phases formed. Calcining KMnO4 at 1000 °C/3h led to the formation of δ-MnO2 materials. The morphological features of Mn2O3 and Mn3O4 materials exhibited different sizes and shapes, including nanostone-like, nanorod-like, and nanoflakes morphologies. The thermal analysis revealed significant differences in weight loss and thermal events, including exo and endothermic peaks. The Raman spectra and UV–Vis DRS measurements data support the formation of Mn-based oxides. The highest NIR reflectance for the various synthesized materials of Mn3O4 phase indicates a reflectance of 68 % in the solar region and 91 % in the color pigment region.

Surface adsorbed–H2O promoted aerobic oxidation of biomass–derived alcohols on MnOx catalysts

Manganese oxides (MnOx) have been emerged as highly active catalysts for the aerobic oxidation of biomass-derived compounds. Herein, a facile urea–redox hydrothermal method was employed to scalable synthesis of MnOx oxides with surface abundant unsaturated Mn and O species. The defective MnOx (MnOx–D) catalyst exhibits remarkable catalytic performance, enabling the room-temperature aerobic oxidation of biomass–derived alcohols with yields exceeding 99%. This represents a substantial 90.8-fold increase in activity compared to commercial MnO2. Moreover, MnOx–D catalyst demonstrates broad substrate scopes for various biomass–derived alcohols and displays recyclability for the aerobic oxidative conversion of 5-hydroxymethylfurfural (HMF) over five cycles. Through a comprehensive analysis involving X–ray photoelectron spectroscopy (XPS), in–situ infrared (IR) spectroscopy, and controlled experiments, it is established that the presence of surface–adsorbed H2O species on MnOx–D catalyst significantly influences its catalytic performance. Mechanism studies reveal that the aerobic oxidation of biomass–derived R–CH2–OH compounds into the corresponding aldehydes can proceed via radical and non–radical pathways. Notably, the catalytic activity of MnOx–D catalyst in both pathways is mediated by the surface adsorbed H2O species. In the radical route, surface adsorbed H2O and O2 species are converted into active •OH radical species, while in the non–radical route, surface adsorbed H2O can form a complex of HMF––H2O species. Both processes enhance the abstraction of H from the O–H and C–H bonds in the R–CH2–OH compounds on MnOx–D catalyst. This discovery could potentially guide the development of efficient metal oxidic catalysts for the oxidation of biomass–derived R–CH2–OH compounds.

Precisely constructing orbital coupling-modulated iron dinuclear site for enhanced catalytic ozonation performance

The advancement of atomically precise dinuclear heterogeneous catalysts holds great potential in achieving efficient catalytic ozonation performance and contributes to the understanding of synergy mechanisms during reaction conditions. Herein, we demonstrate a "ship-in-a-bottle and pyrolysis" strategy that utilizes Fe2(CO)9 dinuclear-cluster to precisely construct Fe2 site, consisting of two Fe1-N3 units connected by Fe-Fe bonds and firmly bonded to N-doped carbon. Systematic characterizations and theoretical modeling reveal that the Fe-Fe coordination motif markedly reduced the devotion of the antibonding state in the Fe-O bond because of the strong orbital coupling interaction of dual Fe d-d orbitals. This facilitates O-O covalent bond cleavage of O3 and enhances binding strength with reaction intermediates (atomic oxygen species; *O and *OO), thus boosting catalytic ozonation performance. As a result, Fe dinuclear site catalyst exhibits 100% ozonation efficiency for CH3SH elimination, outperforming commercial MnO2 catalysts by 1,200-fold. This research provides insights into the atomic-level structure-activity relationship of ozonation catalysts and extends the use of dinuclear catalysts in catalytic ozonation and beyond.

Optimization of Carbon-Defect Engineering to Boost Catalytic Ozonation Efficiency of Single Fe─N4 Coordination Motif.

Carbon-defect engineering in single-atom metal-nitrogen-carbon (M─N─C) catalysts by straightforward and robust strategy, enhancing their catalytic activity for volatile organic compounds, and uncovering the carbon vacancy-catalytic activity relationship are meaningful but challenging. In this study, an iron-nitrogen-carbon (Fe─N─C) catalyst is intentionally designed through a carbon-thermal-diffusion strategy, exposing extensively the carbon-defective Fe─N4 sites within a micro-mesoporous carbon matrix. The optimization of Fe─N4 sites results in exceptional catalytic ozonation efficiency, surpassing that of intact Fe─N4 sites and commercial MnO2 by 10 and 312 times, respectively. Theoretical calculations and experimental data demonstrated that carbon-defect engineering induces selective cleavage of C─N bond neighboring the Fe─N4 motif. This induces an increase in non-uniform charges and Fermi density, leading to elevated energy levels at the center of Fe d-band. Compared to the intact atomic configuration, carbon-defective Fe─N4 site is more activated to strengthen the interaction with O3 and weaken the O─O bond, thereby reducing the barriers for highly active surface atomic oxygen (*O/*OO), ultimately achieving efficient oxidation of CH3SH and its intermediates. This research not only offers a viable approach to enhance the catalytic ozonation activity of M─N─C but also advances the fundamental comprehension of how periphery carbon environment influences the characteristics and efficacy of M─N4 sites.

Optimizing Mn in Prussian blue analogs with double redox active sites to induce boosted Zn2+ storage

Prussian Blue analogs (PBAs) are a suitable aqueous zinc-ion batteries (AZIBs) cathode material, but they face issues related to low specific capacity and cycling lifespan due to insufficient active sites and poor ion de-intercalation structural stability. In this study, Mn-Prussian Blue Analog (Mn-PBA) is fabricated using a simple co-precipitation method and the morphology of Mn-PBA is further optimized through artificially manipulating concentration gradients strategy, effectively enhancing the structural stability of Zn2+ de-intercalation. Furthermore, the introduction of Mn established dual Zn2+ active centers in Mn-PBA (Mn-O and Fe(CN)6]4−/[Fe(CN)6]3−), leading to an increased specific capacity. As a proof of concept for AZIBs, the optimized Mn-PBA-3 cathode exhibits a high reversible specific capacity of 143.5 mAh/g and maintains a capacity retention of 88.5 % after 250 cycles at 1 A/g, surpassing commercial MnO2 (30.5 mAh/g after 100 cycles). Mn-PBA-3 also delivers a high capacity of 79.0 mA h g−1 after 2000 cycles of 10 A/g. The mechanism of the Zn2+ double redox reaction of Mn-PBA-3 has been revealed in detail by in situ Raman and a series of ex situ techniques. Under a high operating voltage window of 0–1.9 V, Zn//Mn-PBA-3 demonstrates a capacity of 99.3 mAh/g after 800 cycles (5 A/g) by assembling zinc ion button battery. This work has reference significance for structurally modulated PBAs used in high performance AZIBs.

Refining Asymmetric Low‐Coordinated Fe‐N3 Motif to Boost Catalytic Ozonation Activity

AbstractIn the quest to boost the intrinsic activity of single‐atom catalysts (SACs), optimizing the electronic properties of metal centers and maximizing active sites play a pivotal role. Here, a facile surface molten salt‐assisted approach for fabricating porous iron‐nitrogen‐carbon catalysts enriched with catalytically accessible single‐atom motifs is reported. Multiple characterization analyses prove that abundant intrinsic defects are generated at the edge sites, resulting in the formation of thermally stable unstitched Fe‐N3 motif. Theoretical investigations unveil that the transition from Fe‐N4 to Fe‐N3 induces structural alteration, resulting in the convergence of Fe‐3d orbital energy to Fermi energy. The low‐coordinated Fe‐N3 motif exhibits higher activation ability, reinforcing its interaction with O3 and weakening the O‐O bond. This leads to a reduction in the reactivity of surface atomic oxygen barriers (O3‐to‐*O/*OO), ultimately achieving efficient catalytic oxidation of methyl mercaptan and its intermediates, achieving performance 20‐fold higher than intact Fe‐N4 catalysts and 625‐fold higher than commercial MnO2. These findings present a comprehensive approach for synthesizing SACs with fully accessible active sites and boosted electronic configurations to advance catalytic ozonation activity.

Bimetal-Initiated Concerted Zn Regulation Enabling Highly Stable Aqueous Zn-Ion Batteries

Aqueous zinc ion batteries are highly sought after for the next generation of sustainable energy storage systems. However, their development is significantly impeded by the presence of undesired zinc dendrites, which greatly reduce their cycle life. It is well-received that surface passivation by introducing foreign metals represents a compelling measure to enhance the stability of Zn anodes. Nevertheless, the vast potential of effecting concerted interplay between multiple metal elements for enhanced overall performance in Zn ion batteries remains elusive, due to the overwhelming challenge in creating uniform textures from hetero-units and understanding the mechanism underlying the synergistic performance gain. In this work, an innovative bimetallic overlaying strategy is proposed that renders possible the synergy between AgZn3 and CuZn5 in effecting uniform Zn deposition in a laterally confined and compact manner. The seeded growth of Zn on the bimetal-modulated interface effectively reduces the nucleation potential barrier, yielding a low nucleation overpotential (25 mV). In full cell testing with a commercial MnO2 applied as the cathode, superb cycling stability, surpassing the results reported in previous works, is achieved. The cell delivers an outstanding remaining capacity of 215 mA h g−1 after 300 cycles with almost no capacity degradation observed. The simple and highly efficient bimetal design, which synergizes the strengths of distinct metals, has the potential to drive innovations in the development of multicomponent aqueous Zn batteries with exceptional performance.

Facile synthesis of δ-MnO2 biotemplated by waste tobacco stem-silks for enhanced removal of Sb(III).

The elimination of antimony pollution has attracted increasing concerns because of its high toxicity to human health and the natural environment. In this work, biomimetic δ-MnO2 was synthesized by using waste tobacco stem-silks as biotemplate (Bio-δ-MnO2) and used in the capture of Sb(III)from aqueous solution. The tobacco stem-silks not only provided unique wrinkled morphologies but also contained carbon element self-doped into the resulting samples. The maximum Sb(III) adsorption capacity reached 763.4mg∙g -1, which is 2.06 times higher than δ-MnO2 without template (370.0mg∙g -1), 4.53 times than tobacco stem-silks carbon (168.5mg∙g -1), and 10.39 times than commercial MnO2 (73.5mg∙g -1), respectively. The isotherm and kinetic studies indicated that the adsorption behavior was consistent with the Langmuir isotherm model and the pseudo-second-order kinetic equation. As far as we are aware, the adsorption capacity of Bio-δ-MnO2 is much higher than that of most Sb(III) adsorbents. FT-IR, XPS, SEM, XRD, and Zeta potential analyses showed that the main mechanism for the adsorption of Sb(III) by Bio-δ-MnO2 includes electrostatic attraction, surface complexation, and redox. Overall, this study provides a new sustainable way to convert agricultural wastes to more valuable products such as biomimetic adsorbent for Sb(III) removal in addition to conventional activated carbon and biochar.

Converting commercial MnO2 into Co-doped LiNi0.5Mn1.5O4 with adjustable disordered/ordered phase ratio by a quaternary molten salt

The electrochemical performances of LiNi0.5Mn1.5O4 (LNMO) materials are strongly correlated with the ratio of disordered to ordered phases. Nevertheless, there are few reports on the adjustment of ordered and disordered phase ratio. In this paper, the ratio of ordered to disordered phases in LNMO is successfully adjusted by using a quaternary molten salt, which is proven by XRD refinement, FT-IR, and XPS. Reductive quaternary molten salt and Co doping are favorable for Ni/Mn cation disorder, leading to the increased disordered phase. LNMO with an appropriate ratio of ordered to disordered phases can exhibit enhanced electronic/ionic transfer rate and structural stability, revealed by electrochemical tests and ex situ characterizations. Therefore, the optimized material delivers a reversible capacity of 121 mA h g−1 at 20 mA g−1 and a long cyclic life with 61 mA h g−1 at 1000 mA g−1 over 1200 cycles. The present work offers a new idea for achieving a regulated ratio of ordered to disordered phases in LNMO.

Bulk‐Phase Grain Boundaries Regulation Enables Highly Reversible Zn Anodes for Rechargeable Aqueous Zn‐Ion Batteries

AbstractDendrites and side reactions of Zn anodes severely restrict the application of aqueous Zn‐based batteries for grid‐scale energy storage. While surface/interface modification strategies have shown some progress in improving Zn anode reversibility, they still fall short in addressing the overall regulation and intrinsic mechanisms from the bulk‐phase perspective. Herein, a bulk‐phase composite Zn/CNTs anodes fabricated by a powder‐metallurgy‐based strategy is introduced. Benefiting from the regulation of grain boundary engineering on local electric conductivity, electric field distributions, and Zn atom absorption energy, the Zn/CNTs anodes effectively suppress dendrite growth and enhance corrosion resistance during Zn stripping/plating cycles. Symmetrical cells equipped with Zn/CNT4 anodes exhibit extended cycling stability with minimal voltage hysteresis (only 22 mV). Furthermore, the full cells incorporating Zn/CNT4 with commercial MnO2 demonstrate superior rate performance and specific capacitance retention after 500 h cycling. This breakthrough opens up new avenues for optimizing metallic anodes at the bulk phase level using powder metallurgy, enabling scalable manufacturing processes, and providing valuable insights for various metal anode systems.

Efficient degradation of organic contaminants in aqueous media using oxygen vacancy-rich MnO catalyst via peroxymonosulfate activation

Understanding the role of oxygen vacancies (OVs) in endowing catalytic activity is important for the design of efficient catalysts for advanced oxidation processes. In this study, we prepared MnO catalysts with different amounts of OVs under an atmosphere of H2 (MnO-H) and N2 (MnO-N) and investigated their acetaminophen (ACE) degradation efficiency via peroxymonosulfate (PMS) activation. MnO-H exhibited the best degradation performance because of its numerous OVs, compared with that of MnO-N and the commercial MnO. Data analysis revealed that ACE degradation proceeded via electron transfer. Density functional theory calculations confirmed that compared with the other catalysts, MnO-H/PMS with more OVs had higher catalytic activity, higher adsorption energy, lower work function, and higher electron transformation. The MnO-H/PMS system was stable at pH 3.0–9.0 and showed good recyclability. We believe that our findings will provide deeper insights into the role of OVs and encourage the use of less toxic metal oxides as catalysts in the selective degradation of organic pollutants in water bodies.

Nitrogen-coordinated cobalt embedded in hollow carbon polyhedron for catalytic ozonation of odor CH3SH at ambient temperature

Metal − organic framework (MOF) derived carbon-based nanocatalysts have received great attention in environmental remediation applications. Herein, a hollow carbon polyhedron with nitrogen-coordinated cobalt embedded has been synthesized by thermal transformation of the core–shell structure ZIF-8@ZIF-67 (marked as ZIF-8@ZIF-67-C). Remarkably, the ZIF-8@ZIF-67-C catalyst could remove almost 98% of CH3SH after running for 60 min, exceeding the reported values (about 30 times higher than that of commercial MnO2 catalysts). Elimination performance experimental results demonstrate that ZIF-8@ZIF-67-C has better anti-interference ability and anti-toxicity properties. The excellent catalytic performance can be attributed to the following facts: unique structure, high conductivity, abundant hierarchical porous structure, and accessible active sites. Theoretical calculation reveals the mechanism is that the Co-N electron bridge promotes Co nanoparticles adsorb O3, providing electrons to O3 and producing 1O2 to further oxidize CH3SH into CO2/SO42−. Also, the ZIF-8@ZIF-67-C catalyst supported on Al2O3 still shows excellent catalytic activity and durability, which deepened the practical application. This work provides a strategy for the development of MOF-on-MOF-derived metal/carbon hybrid materials in environmental applications.

Inhibition of iron chelate degradation in liquid redox desulfurization by nanoscale MnO2 through H2O2 decomposition

AbstractBACKGROUNDSignificant operating costs incurred in the liquid‐phase oxidation process using iron chelate catalytic solution (e.g. LO‐CAT) due to degradation and eventual loss of the iron chelate is a serious deficiency. Hydroxyl radicals formed in the Fenton reaction of ferrous chelate with H2O2, generated during the regeneration of the ferrous chelate with air, are responsible for iron chelate degradation. Although iron chelate degradation may be slowed down or inhibited by the catalytic decomposition of H2O2 into O2 and H2O, what is not yet clear is the impact of H2O2 decomposition by MnO2 on iron chelate degradation. In this work, the effects of H2O2 concentration, MnO2 concentration, oxygen as well as the initial pH value on iron chelate degradation in alkaline Fenton system of Fe2+‐EDTA/H2O2 (where EDTA is ethylenediaminetetraacetic acid) were studied.RESULTSResults showed that the percentage degradation of Fe‐EDTA increased with H2O2 concentration and decreased with H2O2 decomposition. In contrast to commercial MnO2, nanoscale MnO2 had much excellent catalytic activity on the decomposition of H2O2; thus 60 mmol L−1 nanoscale MnO2 inhibited Fe‐EDTA degradation by up to 82%. Furthermore, the inhibition in Fe‐EDTA degradation by H2O2 decomposition on nanoscale MnO2 was independent of pH from 6.0 to 8.5, and was related to oxygen concentration.CONCLUSIONNanoscale MnO2 can effectively inhibit the iron chelate degradation in LO‐CAT, and the significant operational costs associated with iron chelate degradation will be reduced by H2O2 decomposition on recyclable nanoscale MnO2 catalysts. © 2023 Society of Chemical Industry (SCI).

Interstitial carbon-platinum electronic metal-support interaction structure boost synergistic removal of O3 and CH3SH via surface atomic oxygen

Carbon atoms in the interstitial sites of metal nanoparticles have strong influence on heterogeneous catalysis via electronic metal-support interactions (EMSI). Here, the Pt catalysts with interstitial C-Pt EMSI structures were first developed and identified to boost the removal of ozone (O3) and methyl mercaptan (CH3SH). Experimental results showed that the intrinsic activity of the catalysts with low Pt loading (wt%, 0.95 %) was 186 times higher than that of commercial MnO2. This excellent catalytic performance was attributed to dual-site catalytic structures to promote the adsorption/activation of O3 at interstitial C and capture/oxidation of CH3SH at Pt simultaneously. More importantly, the interstitial C sites retained surface atomic oxygen (*O) with excellent reactivity and lowered the energy barrier of CS bond breakage, thus achieving efficient decomposition of CH3SH into CO2/SO42-. This work provides high-performance catalysts and new mechanistic insights for the synergistic control of O3 and CH3SH.

Binder‐Free Electro‐Deposited MnO2 @3D Carbon Felt Network: A Positive Electrode for 2V Aqueous Supercapacitor

Electrochemical supercapacitors have been considered the most promising energy storage system due to their attractive features, high power, energy density, and good cycle performance. This work investigates the capacitor performance of the tailor‐made electro‐deposited (ED) MnO2‐coated 3D‐carbon felt (CF) as a positive electrode. Manganese, a well‐known transition metal, has good electrochemical activity in various electrolyte conditions with broad operating potential and high specific capacity. The ED MnO2@CF delivers a maximum specific capacitance of and 231.5 Fg−1 at 10 mV s−1 in three electrode configurations. The asymmetric cell is developed using MnO2@CF as a positive electrode and the cell deliveres a maximum capacitance of 187.5 F g−1 at 0.2 A g−1 at a high‐voltage window of 2 V. The cycle life of the asymmetric capacitor is also tested up to 10 000 cycles, and the cell deliveres a round trip efficiency of 99%. To elucidate further the high‐voltage window (2 V) of the present work, an asymmetric cell configuration is fabricated using commercial MnO2 and the performance characteristics are also compared.

Improved Interface Stability and Zinc‐Ions Distribution Achieved by Functional Protective Layer Containing Abundant Oxygen Sites and Regular Channels for Long‐Life Zinc‐Metal Anodes

AbstractAqueous zinc (Zn)‐ion batteries (AZIBs) have attracted much attention for the high safety, economy and nontoxic property, but further practical applications are still hindered due to the severe interfacial corrosion and annoying dendrite growth. Herein, a functional protective layer (FPL) containing abundant oxygen sites and regular channels is proposed as the surface coating to stabilize the Zn‐metal anode. Specifically, transferred free water molecules and mitigated Zn‐ions can be attracted by these polar oxygen sites, beneficially reliving corrosion behavior, reducing side reactions and inducing uniform Zn deposition. Furthermore, the cross‐linked structure with opening channels of FPL benefits electrolyte to quickly arrive the electrode surface and maintain the superior movement of Zn‐ions. As a result, a superior cycling performance with high stability of 450 h at 5 mA cm−2 and excellent rate behavior have been endowed by Zn electrode loading FPL. In the exploration of practical utilization, full battery consisting of Zn@FPL anode and cathode adopting commercial MnO2 powder also exhibits an outstanding capacity retention of 98.9 % after 300 cycles at 0.5 A g−1. The proposed strategy of constructing a protective layer with functional sites and opening structure shows a good guiding significance for protecting Zn‐metal anode.

Designing of 3D MnO2-graphene catalyst on sponge for abatement temperature removal of formaldehyde

The Mn-based catalysts, with low cost and high activity, are believed to be the effective composites for eliminating in-door formaldehyde (HCHO), while the powdered form nanosized catalysts are hardly to apply for practical application. Herein, hetero-structure of nanosheets manganese oxide (MnO2) encapsulating N-doping graphene sphere (GS) were deposited in network-like sponge for constructing 3D catalyst. The prepared MnO2-GS-Sponge composite catalyst exhibited excellent performance for removing HCHO at room temperature compared with GS and commercial MnO2. The MnO2-GS with larger specific surface area (209.1 m2·g−1) was dispersed evenly in 3D network of sponge, which facilitated exposing more activate sites and achieving fast transport kinetics accelerating catalytic reaction for converting 97.1 % of 100 ppm of HCHO continuously to CO2 for 120 h. Moreover, rely on the chemisorption of amino groups on N-doping GS surface, HCHO could be enriched even at low concentrations and efficient elimination (from 1000 ppb to12 ppb, at 35 ℃ in 48 h). The average oxidation state and infrared spectra analysis suggested that abundant oxygen vacancies on MnO2-GS-Sponge could be identified as surface-active sites of converting HCHO into the intermediates of dioxymethylene and formate. This work might inspire the designing 3D composite material for potential application in other fields of environmental engineering or energy industrial.

Crystal form modulation enables high-performance manganese dioxide cathode for aqueous zinc ion battery

Manganese dioxide (MnO2) is a promising cathode candidate for advanced rechargeable Zn-ion batteries (ZIBs) owing to its low cost, high theoretical capacity and high output voltage. However, the poor stability and low practical capacity has greatly hampered its commercialization. Herein, we demonstrate a crystal form modulation strategy to enhance the capacity and cycling durability of commercial γ-MnO2 as robust ZIBs cathode material. By introducing new β-MnO2 crystal form with compact (1 × 1) tunnel structure after simple calcination, the γ- and β- co-existed MnO2 (denoted as m-MO) shows enhanced electrical conductivity and structural stability. Consequently, the m-MO cathode exhibits an excellent capacity of 273.6 mAh g–1 at 0.25 A g–1 with good cycle stability, much higher than the pristine γ-MnO2 cathode (156.7 mAh g–1). Furthermore, an aqueous ZIBs based on m-MO cathode delivers a large peak energy density of 349.1 W h kg–1 at 0.322 kW kg–1 and power density of 4.77 kW kg–1 at 123.01 W h kg–1. This work presents an effective crystal form modulation strategy to construct high-performance ZIBs cathodes based on commercial MnO2, which is highly potential for further commercial applications.