Nanoflower-like Morphology Research Articles

Facile one-step solvothermal synthesis of Co3O4/CuO nanoflowers as an excellent catalyst for CO oxidation in coal mines

In the present study, Cobalt oxide (Co3O4)/Copper oxide (CuO) nanoflower catalysts were synthesized through a one-step solvothermal method, and the impact of various factors, including reaction time, on the catalytic activity of the catalysts towards carbon monoxide (CO) was investigated. The results showed that the catalysts synthesized at 140 °C and a reaction time of 4 h provided the best catalytic performance for carbon monoxide, and the regular nanoflower-like morphology provided a larger specific surface area as well as a greater number of active sites, allowing the instantaneous 100 % elimination of CO at 200 °C. Additionally, a plausible reaction mechanism was elucidated, wherein CO initially adsorbed onto the sample's surface, subsequently reacting with lattice oxygen to form intermediate carbonate species. This process ultimately led to the production of carbon dioxide (CO2), followed by the desorption of CO2 molecules from the sample's surface. The results demonstrate that these composite catalysts effectively mitigate CO levels during CO over limit in coal mines, thereby enhancing the safety of production personnel.

Hierarchical nanoflowers of Bi/Fe-based selenide as a bifunctional electrocatalyst for alkaline water electrolysis

The current study presents a freestanding bifunctional electrocatalyst comprising hierarchically assembled Bi/Fe-based selenide with a nanoflower-like morphology on Ni foam for water electrolysis application. The impact of systematically adding Fe ions to Bi2Se3 on the phase and morphology is elaborately discussed. It is shown that tuning the Bi/Fe molar ratio governs the phase, electronic bandgap, and morphology, driven by the evolution of hetero-interfacial chemistry. The existence of multivalent metal ions, lattice defects, and an extended surface area remarkably improves the electrocatalytic activity. The optimized nanoflower-like composite electrode (1Bi1Fe-Se@NF) exhibits robust electrocatalytic efficacy with extremely low overpotentials of ∼53 mV and ∼230 mV at 10 mA cm−2 for hydrogen and oxygen evolution reactions, respectively. The symmetrical alkaline electrolyser, utilizing 1Bi1Fe-Se@NF electrodes (+,−), operates at a cell voltage of ∼1.52 V at 10 mA cm−2, lower than the device equipped with commercial Pt/C@NF (-) and RuO2@NF (+) (∼1.57 V). Even after 100 h of operation at 50 mA cm−2, the symmetrical cell maintains a stable voltage, highlighting the outstanding bifunctional catalytic activities of noble metal-free 1Bi1Fe-Se@NF for overall water electrolysis.

Engineering 2D Mg-Al-layered double oxides with highly dispersed and enhanced basic sites for efficient ambient NO2 reactive removal

The release of nitrogen dioxide (NO2) into the atmosphere significantly contributes to air pollution, posing threats to both the environment and human health. Selective adsorption technologies have gained attention for their potential to mitigate NO2 emissions under ambient conditions. However, certain solid adsorbents lack accessible active basic sites, a crucial requirement for high NO2 adsorption capacities due to the acidic nature of NO2. Metal-based layered double oxides (LDOs), derived from layered double hydroxides (LDHs), show promise for ambient NO2 adsorption due to their layered structures, strong basic properties, and adjustable adsorption affinity. In this study, we synthesized a series of M-Al-LDO/A (M = Ni, Co, and Mg) using a facile aqueous miscible organic solvent treatment (AMOST) method. The newly synthesized M-Al-LDO/A exhibited a 2D nano flower-like morphology with expanded surface area, increased pore volume, and enhanced accessible basic sites. Dynamic breakthrough experiments demonstrated the exceptional NO2 adsorption capacity of Mg-Al-LDO/A (4.67 mmol g−1) under ambient conditions, surpassing Mg-Al-LDO/CP (0.13 mmol g−1) synthesized from the conventional method by more than 35 times. Temperature-programmed desorption (TPD) results and spectroscopic analyses revealed that the improved NO2 capacity of Mg-Al-LDO/A resulted from the highly dispersed and increased basic sites (Mg-O2-). These findings hold promise for advancing efficient and environmentally friendly NO2 adsorption materials, critical for addressing the challenges posed by NO2-induced air pollution and safeguarding air quality.

Electric field-assisted laser ablation fabrication and assembly of zinc oxide/carbon nanocomposites into hierarchical structures for supercapacitor electrodes.

One of the major challenges in the field of electrochemical energy storage device performance improvement is the development of suitable synthetic materials for electrodes that can provide high power and high energy density features combined with their long-term stability. Here, we have developed a novel two-step approach based on DC glow discharge plasma pre-treatment of a carbon cloth substrate followed by electric field-assisted laser ablation for the synthesis of ZnO/C nanocomposites in a liquid and their simultaneous assembly into hierarchically organized nanostructures onto the pre-processed carbon cloth to produce a supercapacitor electrode. To form such nanostructures, a processed carbon cloth was included in the electrical circuit as a cathode during laser ablation of zinc in water, while a zinc target served as an anode. A series of studies have been performed to explore the structure, morphology, composition and electrochemical characteristics of the synthesized ZnO/C nanocomposites. Application of the external field provided additional possibilities for tuning the particle morphology. The parameters of the obtained nanostructures were shown to depend on the direction of the applied electric field and liquid composition. SEM studies revealed a nanoflower-like morphology of the prepared nanomaterial having potential in supercapacitor applications due to a large surface area. The ZnO/C nanoflowers, deposited onto a carbon cloth substrate, were tested for energy storage by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis. The results showed a pseudocapacitor behavior with a maximum specific capacitance of about 3045 F g-1 (at a scan rate of 1 mV s-1). These results demonstrate a promising storage efficiency of the synthesized ZnO/C nanocomposite as a material for supercapacitors.

Nanoflower like FeNi–B–P based on bifunctional nickel foam as a binder free electrocatalyst for high-efficiency oxygen evolution reaction

Nickel foam as a current collector and substrate material is frequently utilized in electrochemical applications such as supercapacitors, batteries and the promising oxygen evolution reaction (OER). Herein, nanoflower like FeNi–B–P self-growing on nickel foam (FNBP/NF) is developed by electrodeposition and the B/P molar ratios within FNBP/NF are regulated to investigate the best OER performance at different ratios of boron and phosphorus. Moreover, the NF in this study achieves dual functionalization. It serves not only as a self-supporting formwork to maintain the intrinsic conductivity of the composite, but also as nickel source to provide attachment points and a growing environment. Thanks to the strong skeleton of NF, the catalyst shows extreme stability, as it remains almost constant during a 24 h chronopotentiometry test. Meanwhile, the convective effect of the NF prevents the accumulation of gas products at the interface, accelerating the precipitation of O2 and reducing contact resistance. Through electrochemical treatment, high-valence iron and nickel ions exhibit a synergistic effect that accelerates the coupling of O–O bonds, thereby promoting the evolution of O2. In 1.0 M KOH solution, the OER performance of FNBP/NF has been explored, when the current densities are 10 and 50 mA cm−2, the corresponding overpotentials are 253 and 318 mV, respectively, suggesting satisfactory electrocatalytic activity. Field emission scanning electron microscopy reveals a unique nanoflower-like morphology of FNBP/NF, providing abundant accessible sites for effective contact between the active substance and reactants. This study introduces bifunctional NF in OER catalysis to achieve dual synergistic effects, both synergistic effects of high-valence Fe–Ni ions and convective effect of NF, which accelerate O2 releasing and effectively reduce contact resistance, presenting a novel approach to achieving high-efficiency oxygen evolution.

A novel electrochemical sensing platform based on double-active-center polyimide covalent organic frameworks for sensitive analysis of levofloxacin.

The development of a simple and sensitive electrochemical sensing platform for levofloxacin (LVF) analysis is of great significance to human health. In this work, a covalent organic framework (TP-COF) was in situ grown on the surface of Sn-MoC nanospheres with nanoflower-like morphology through a one-pot method to obtain the TP-COF@Sn-MoC composite. The prepared composite was used to modify a glassy carbon electrode (GCE) to realize the sensitive detection of levofloxacin. TP-COF was formed by polycondensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and pyromellitic dianhydride (PMDA), in which C = O and C = N groups served as double active centers forthe recognition and electrocatalytic oxidation of the target molecule. Meanwhile, the introduction of Sn-MoC improved the conductivity of the electrode. The TP-COF@Sn-MoC composite produced a strong synergistic effect and showed a high electrocatalytic ability toward levofloxacin oxidation. The linear range of LVF was 0.6-1000μM and the limit of detection (LOD) was 0.029μM (S/N = 3). In addition, the sensor has been successfully applied for the analysis of LVF in human urine and blood serum samples with acceptable recovery rates, demonstrating that the sensor was promising in practical applications.

Revealing dynamic structural evolution of V and P co-doping-induced Co defects as large-current water oxidation catalyst

Metallic defects can improve catalysts' intrinsic activity by regulating its electronic structure and enhancing conductivity. However, the impact of these defects on the kinetics of the oxygen evolution reaction (OER) has not been extensively studied. Here, a V/P codoped nanoflower-like CoS2 catalyst with rich Co defects on carbon cloth (V,P-CoS2/CC) is fabricated by feasible directional construction. The V,P-CoS2/CC validates extraordinary OER performance with overpotentials of 227/300 mV at 10/100 mA cm−2 and robust long-term stability. The enhanced single-electron spin resonance signal and higher lifetime strength indicate an increased number of surface Co defects induced by V/P codoping. Density functional theory (DFT) calculations verify that Co defects induced by V/P codoping of the surface reconstituted V-CoOOH/CoS2 catalyst can optimize the adsorption/desorption energy of oxygen-containing intermediates to accelerate OER process. Besides, the nanoflower-like morphology with large electrochemical active surface area and good hydrophilicity facilitates electrolyte diffusion/gas emission, thereby synergistically elevating OER performance.

Antagonistic activity of a novel chitosan-selenium nanoflower against common aquaculture pathogen Aeromonas caviae

Aquatic pathogens contribute to the most severe economic loss in fishes. Nanoparticles are being developed as potent antimicrobial agents against various pathogens. The bacteria Aeromonas caviae is one of the most common aquatic pathogens that infects the majority of economically important fishes causing significant losses to the aquaculture industry. This study involved synthesizing and characterizing of a novel chitosan‐selenium nanoflower employing multiple spectroscopic and microscopic approaches. The UV‐vis spectra obtained at 265 nm indicated the formation of the Chitosan‐selenium nanoflower. The particle size analysis revealed the size of the nanoflowers to be 186.3 nm. The transmission electron micrographs revealed a unique nanoflower-like morphology. XRD spectrum revealed amorphous nature. The Raman spectrum showed a strong resonance peak at 254 cm−1 which is a characteristic absorption band for monoclinic Se and α‐Se. Cytotoxicity analysis of the synthesized nanoflowers against isolated fish pathogen Aeromonas caviae showed increasing toxicity in a dose‐dependent manner with maximum cytotoxicity of 75.06% at 1000 µg/mL. The DCFDA assay was conducted to estimate the increase in reactive oxygen species (ROS) production, and the highest percentage increase in ROS of 96.02% was observed at 1000 µg/mL. The lipid peroxidation assay was performed by quantification of the lipid oxidation product malondialdehyde (MDA). The highest percentage of lipid peroxidation was found to occur at a dose of 500 µg/mL. As a result, the synthesized chitosan‐selenium nanoflowers can be exploited as a promising antibacterial treatment against the fish pathogen Aeromonas caviae.

Nano-flower like CoFe-layered double hydroxide@reduced graphene oxide with efficient oxygen reduction reaction for high-power air-cathode microbial fuel cells

Microbial fuel cells (MFCs) are “self-sufficient” renewable energy sources that utilize the redox processes inherent in microbial metabolism to generate an electrical potential. However, the cathodic region of these fuel cells typically utilizes an oxygen reduction reaction (ORR) operating at high overpotential and slow reaction kinetics significantly, restricting the power generation capacity of MFCs. Herein, to improve the cathodic reduction efficiency, we synthesized CoFe-layered double hydroxides (LDH) on partially-reduced graphene oxide (p-rGO) via electrostatic interaction. In contrast to pure CoFe-LDH, CoFe-LDH@p-rGO composite possessed a three-dimensional uniform porous nanoflower-like morphology, giving the catalyst a high surface area for efficient catalysis. The proportions of CoFe-LDH to p-rGO were optimized to minimize layer stacking through strong π-π bond and van der Waals force, maximizing the overal electron transfer numbers n (3.66), with the lowest charge transfer resistance Rct (38.5 Ω). As a result, this novel catalyst combined the rich Co/Fe metal center catalytic active sites and interlayer structure of CoFe-LDH, with the high electrical conductivity of p-rGO to accelerate the electron transfer rate of ORR. Air-cathode microbial fuel cell (ACMFC) utilizing CoFe-LDH@p-rGO catalyst showed comparable output voltage of 423 mV to Pt/C catalyst, and a comparably high-power density of 204 mW m−2. This work provides a new path towards development of nanostructured non-noble metal catalysts for the optimization of oxygen reduction reaction in high-power ACMFCs.

Surface Dual Metal Occupations in Fe-Doped FexBi2-xO3 Induce Highly Efficient Photocatalytic CO2 Reduction.

CO2 possesses extraordinary thermodynamic stability, and its reduction reaction involves multiple electron-transfer processes. Thus, high-density electron occupation on a catalyst surface is an effective driving force for improving the photocatalytic activity. Here, we report on the fabrication of Fe-doped Bi2O3 catalysts (denoted as FexBi2-xO3) with different Fe contents using the solvothermal method. The self-assembled catalyst has a nanoflower-like morphology, and its performance of CO2 reduction to CO is improved largely dependent on the Fe content. In the sample with a 7.0% Fe content (Fe0.07Bi1.93O3), the CO evolution rate reaches 30.06 μmol g-1 h-1, which is about 6 times higher than the 4.95 μmol g-1 h-1 of pristine Bi2O3, and shows excellent photostability after three cycles, with each cycle lasting for 7 h. Theoretical calculation and spectral characterization reveal that such a good CO2 reduction reaction performance arises from effective surface occupation of Fe, which not only enhances sunlight absorption but also significantly increases the surface electron density on the double metal active sites. This work provides a new strategy for improving the photocatalytic performance by surface metal doping in some metal oxide photocatalysts.

Synergistic Effect of P Doping and Mo-Ni-Based Heterostructure Electrocatalyst for Overall Water Splitting.

Heterostructure construction and heteroatom doping are powerful strategies for enhancing the electrolytic efficiency of electrocatalysts for overall water splitting. Herein, we present a P-doped MoS2/Ni3S2 electrocatalyst on nickel foam (NF) prepared using a one-step hydrothermal method. The optimized P[0.9mM]-MoS2/Ni3S2@NF exhibits a cluster nanoflower-like morphology, which promotes the synergistic electrocatalytic effect of the heterostructures with abundant active centers, resulting in high catalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte. The electrode exhibits low overpotentials and Tafel slopes for the HER and OER. In addition, the catalyst electrode used in a two-electrode system for overall water splitting requires an ultralow voltage of 1.42 V at 10 mA·cm-2 and shows no obvious increase in current within 35 h, indicating excellent stability. Therefore, the combination of P doping and the heterostructure suggests a novel path to formulate high-performance electrocatalysts for overall water splitting.

Optical and Dielectric Characterization of Nanoparticle-Based Cu2Ni1+xSn1–xS4 Nanosphere Synthesized by Facile Solvothermal Method

Here, we have reported an excellent optical, dielectric, and electrical behavior of Cu2Ni1+xSn1–xS4 (CNTS) nanospheres synthesized by the facile solvothermal technique. From its structural analysis, the polycrystalline nature of the material was confirmed due to the presence of the sphalerite phase along with several secondary phases, demonstrating the structural tuning possibilities with a compositional variation. Further analysis of the electronic structure showed the presence of Cu+1, Ni+2, Sn+4, and S–2 valence states in the composition. The nanoflower-like morphology made up of nanospheres remained the same even after the compositional variation and enhanced the light-trapping effect. However, the increase in the optical band gap and decrease in the refractive index showed distinctive properties with the Ni concentration variation. The frequency and temperature-dependent behavior of dielectric parameters, conductivity, impedance, and electric modulus parameters broadened the application possibilities along with the optoelectronic properties. The increase in AC conductivity with temperature enabled the hopping of charge carriers, and properties like an increase in the loss factor at a lower frequency and higher temperature made the nanomaterials favorable for devices based on high-power circuits. The decrease in impedance values indicated less current dissipation in lower-frequency regions, and the electric modulus parameter showed non-Debye-type behavior. The tunable optical, dielectric, and electrical properties of the CNTS materials widen the cutting-edge optoelectronic application possibilities.

Heterogenized molecular Pd(ii) catalyst on ultrathin 2D metal–organic frameworks with nanoflower-like morphology for isonitrile-involved cyclization reaction

An ultrathin 2D MOF based catalyst with fully exposed single-site Pd(ii) active centers shows superior catalytic efficiency for the isonitrile-involved cyclization reaction compared to 3D MOF based Pd(ii) catalyst and homogeneous counterpart.

Hydrothermally synthesized 2H-MoS2 under optimized conditions – A structure and morphology analysis

In this study, we obtained the optimized conditions to synthesize pure semiconducting 2H-MoS2 nanomaterial, using a facile and scalable hydrothermal route under the variation of growth parameters such as reaction temperature, reaction time and sulfur precursors. The structural and phase identification of obtained MoS2 powders was analysed using XRD and raman spectroscopy. The reproducible formation of pure 2H-MoS2 phase is reported for the optimized reaction time of 22 h at a temperature of 200 °C using thiourea as sulfur source, with a high yield of 77.4%. FESEM analysis revealed nanoflower-like morphology of average diameter of 300–400 nm with identifiable petals of thickness ∼25 nm for the formed 2H-MoS2 under the optimized conditions. The crystallite size, strain and dislocation density were estimated theoretically using Williamson-Hall plots for the MoS2 formed under the variation of growth temperatures. Tensile strain values were obtained for MoS2 formed using thiourea, which correlated only with phase transitions from mixed 1 T/2H-MoS2 to pure 2H-MoS2. In contrast, only mixed 1 T/2H-MoS2 phase were obtained for MoS2 powders using L-Cysteine, and correspondingly the strain values were extremely small, which may be due to no phase transition observed and presence of nanosheets without curved petal-like features. The results of this study provide optimized condition for the formation of semiconducting 2H-MoS2 nanomaterial by a scalable route. This is useful for low-cost fabrication of flexible nanoelectronic devices such as non-volatile ReRAMs, supercapacitors and sensors based on 2H-MoS2.

Fabrication of Z-scheme CdS/H5PMo10V2O40/g-C3N4 for the photocatalytic depolymerization of lignin into aromatic monomers

As the most abundant resource composed of aromatic groups in nature, lignin harbors significant potential for the production of bio-based fuels and chemicals. In recent years, solar-driven photocatalysis with its mild, low cost and environmental benign, has been employed for lignin depolymerization. Herein, we designed a Z-scheme CdS/H5PMo10V2O40/g-C3N4 (CdS/HPA-2/CN) photocatalyst via hydrothermal method for the photocatalytic depolymerization of lignin. The prepared CdS/HPA-2/CN presents a nanoflower-like morphology with the average diameter of ∼600 nm. With the presence of electron-mediated HPA-2, CdS/HPA-2/CN exhibits the enhanced separation and transfer capacity of photogenerated charge carriers through Z-scheme mechanism. Result shows that the total yield (Y) of vanillin and vanillic acid from lignin depolymerization over optimized CdS/HPA-2/CN can reach to 32.7 mg/g lignin in DMF/formic acid (v/v = 40/10) for 4 h. Reusability experiment of optimized CdS/HPA-2/CN displays that Y (26.5 mg/g lignin) can still reach to 81.0% of initial one after three cycles. Qualitative analysis of depolymerized products reveals that most components are aromatic compounds with the dominant products of vanillin and vanillic acid. Evidence also shows that photocatalysis promotes the reaction and small molecular products increased significantly after depolymerization. In addition, mechanism experiments and electron spin resonance tests exhibit that h+, ·O2− and ·OH took part in lignin depolymerization together and the effect sequence was ·O2− > ·OH > h+. In this work, as an electron mediator, HPA-2 provides the inspiration for construction of Z-scheme heterojunction, and CdS/HPA-2/CN exhibits enormous potential in lignin depolymerization by photocatalysis.

Synthesis, Structural and Optical Properties of ZrBi2Se6 Nanoflowers: A Next-Generation Semiconductor Alloy Material for Optoelectronic Applications.

ZrBi2Se6 nanoflower-like morphology was successfully prepared using a solvothermal method, followed by a quenching process for photoelectrochemical water splitting applications. The formation of ZrBi2Se6 was confirmed by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The estimated value of work function and band gap were found to be 5.5 and 2.26 eV measured using diffuse reflection spectroscopy and ultraviolet photoelectron spectroscopy, suggesting the potential candidate for water splitting. The highest current density of 9.7 μA/cm2 has been observed for the ZrBi2Se6 photoanode for the applied potential of 0.5 V vs SCE. The flat-band potential value was −0.46 V, and the 1.85 nm width of the depletion region is estimated from the Mott–Schottky (MS) analysis. It also reveals that the charge carrier density for the ZrBi2Se6 nanoflowers is 4.8 × 1015 cm–3. The negative slope of the MS plot indicates that ZrBi2Se6 is a p-type semiconductor. It was observed that ZrBi2Se6 nanoflowers had a high charge transfer resistance of ∼730 kΩ and equivalent capacitance of ∼40 nF calculated using electrochemical impedance spectroscopy (EIS) measurements. Using chronoamperometry, the estimated rise time and decay time were 50 ms and 0.25 s, respectively, which reveals the fast photocurrent response and excellent PEC performance of the ZrBi2Se6 photoanode. Furthermore, an attempt has been made to explain the PEC activity of ZrBi2Se6 nanoflowers using an energy band diagram. Thus, the initial results on ZrBi2Se6 nanoflowers appear promising for the PEC activity toward water splitting.

Surfactant-assisted facile synthesis of petal-nanoparticle interconnected nanoflower like NiO nanostructure for supercapacitor electrodes material

Nickel oxide (NiO) nanostructures with diverse morphology were prepared by facile sol–gel route using cationic, anionic, and non-ionic surfactants as stabilizing agents. The effects of surfactants on the physical and morphological properties of NiO were investigated. In addition, the electrochemical properties of grown products were also studied. We have observed that cationic surfactant (CTAB) leads to petal-nanoparticle interconnected nanoflower-like morphology. The electrochemical study revealed that all electrodes have pseudocapacitive nature with Faradic charge-storage mechanism. The CTAB assisted electrode owns large specific capacitance/energy density/power density of 397F/g/27.57 Wh/kg/0.54 KW/kg at 1 A/g current density in 1.0 M KOH electrolyte with superior cycling stability. The formation of nanoflower-like morphology in CTAB assisted electrode provides a larger surface area for ions transportation, higher conductivity, fast charge transfer, higher current density, and high electrochemical active surface area, attributing to boosted supercapacitive behavior of synthesized electrodes.

Facile synthesis of Sm doped ZnO nanoflowers by Co-precipitation method for enhanced photocatalytic degradation of MB dye under sunlight irradiation

Rare earth (RE) metal doping into the metal oxide semiconductor (MOS) is considered an effective way to boost photocatalytic performance for its capability to decelerate the electron-hole pair recombination upon excitation. In the current work, Zinc oxide (ZnO) nanoflowers were synthesized via facile co-precipitation method with varying concentrations of samarium (Sm) ions. Several techniques were used to analyze the structural, morphological, optical, and elemental composition properties of the prepared photocatalyst. FE-SEM studies revealed the nanoflower-like morphology, whereas the structural properties confirm the wurtzite crystal structure of ZnO which is identified by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. Additionally, the observed shift in XRD planes toward lower theta values justifies the incorporation of Sm3+ ions into the Zinc Oxide lattice. The photo induced activity of Sm doped ZnO nanoflowers was studied by the degradation of methylene blue (MB) under sunlight irradiation, especially 5% Sm-ZnO shows the highest degradation efficiency with 96% within 90 min. The photocatalytic degradation mechanism and scavenger test towards MB using Sm doped ZnO NFs have also been discussed.

In Situ Construction of Hierarchical Nanoflower-Like MnO2/Biomass-Based Boron-Doped Carbon Spheres for Oxygen Evolution Reaction

Herein, a novel boron doped carbon sphere (BCS) and its derived MnO2 nanocomposite electrode (abbreviated as MnO2/BCS) are firstly prepared via a facile hydrothermal strategy, which was successfully confirmed via a combined characterization including SEM, TEM, EDS, FT-IR, Raman and XPS. Due to the introduction of BCS, the MnO2/BCS shows hierarchical nanoflower-like morphology with a smaller particle size and higher specific surface area than that of pristine MnO2. Importantly, the resultant MnO2/BCS with proper addition of BCS displays superior OER performance than those of the pristine MnO2. The electrochemical measurement results demonstrate that the optimal MnO2/BCS0.08 can give rise to a lowest overpotential mere 170 mV at 10 mA·cm−2, onset potential reaching 1.33 V together with smallest Tafel slope value of 31.43 mV dec−1, which can be mainly due to the higher conductivity, faster charge transfer kinetics and higher electrocatalytic active sites of the MnO2/BCS0.08 than those of other counterparts. Undoubtedly, the incorporation of BCS is mainly responsible for the enhanced electrocatalytic activity. Furthermore, the MnO2/BCS0.08 also has a prominent long-term stability in alkaline conditions. In conclusion, our present work demonstrates an effective strategy to enhance the OER performance of MnO2 by incorporation of the carbon nanomaterials.

Amorphization activated RhPb nanflowers for energy-saving hydrogen production by hydrazine-assisted water electrolysis

Utilizing the easy oxidation reaction of small molecules to replace sluggish oxygen evolution reaction shows high potential to lower the potential of water splitting for hydrogen production, which depends on identification of active catalysts. Herein, amorphous RhPb nanoflowers (a-RhPb NFs) are synthesized through one-step hydrothermal reaction, in which CO is derived from decomposition of formaldehyde as a reducing agent and structure directing agent. Benefiting from 3D nanoflower-like morphology, amorphous structure, and strong electronic interaction, the a-RhPb NFs show excellent catalytic performance for hydrogen evolution and hydrazine oxidation reactions, requiring overpotentials of −36 and 18 mV to achieve the current density of 10 mA cm−2, respectively. Inspiringly, when a-RhPb NFs serve as bifunctional electrocatalysts for hydrazine-assisted water splitting, low potentials of 0.095 and 0.321 mV are achieved at 10 and 100 mA cm−2, respectively. This study offers an attractive approach to synthesize amorphous bimetallic electrocatalysts towards efficient hydrogen production and beyond.