Solution-processed Cu2ZnSnS4 thin film with mixed solvent and its application in superstrate structure solar cells

Cu₂ZnSnS₄ (CZTS) thin film solar cells become an interesting research topic due to some advantages of the CZTS thin film such as having nontoxic and abundant components, a low price and excellent optoelectronic properties. In this work, a solution-based preparation method was developed to fabricate a CZTS solar cell with a superstrate structure of FTO/TiO₂/CdS/CZTS/P3HT/Cu by using mixed solvent. Nanocrystalline TiO₂ porous thin film was used as the bottom layer for deposition of CZTS to increase the interfacial area of CZTS. To deposit CZTS inside the porous structure leading to a good contact of CZTS with porous TiO₂ thin film, the CZTS precursor particle size is successfully regulated by changing the volume ratios of N,N-dimethylformamide and ethanol. More importantly, small size CZTS precursor particles can easily enter into the porous structure of nanocrystalline thin film leading to a good interfacial contact, which allowed the effective improvement of the light-to-electric conversion efficiency for the present superstrate CZTS solar cell. This work may provide a promising way for the design of high-efficient superstrate solar cells.

Solution processed superstrate CZTS solar cells with mixed solvent to adjust CZTS particle size.     

Correction: Extremely low coercivity in Fe3O4 thin film grown on Mg2TiO4 (001)

Correction for ‘Extremely low coercivity in Fe₃O₄ thin film grown on Mg₂TiO₄ (001)’ by X. H. Liu et al., RSC Adv., 2017, 7, 43648–43654.

The authors regret that two co-authors were not included in the author list for the original article. The corrected author list, to which A. C. Komarek and C. F. Chang have been added, is presented herein. The corresponding correction to the first sentence of the Acknowledgements is presented below:“We thank L. H. Tjeng from the MPI CPfS for stimulating discussions”.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Electrical and electrochemical properties of Li2M(WO4)2 (M = Ni,Co and Cu) compounds

Li₂M(WO₄)₂ (M = Co, Cu or Ni) materials have been synthesized using the solid-state reaction method. X-ray diffraction measurements confirmed the single phase of the synthesized compounds in the triclinic crystal system (space group P$\bar{1}$). The SEM analyses revealed nearly spherical morphology with the particle size in the range of 1–10 μm. The IR spectra confirm the presence of all modes of WO₄²⁻. The impedance spectroscopy measurements showed the presence of grain boundaries and allow determination of the conductivity of the synthesized materials at room temperature. As positive electrode materials for lithium ion batteries, Li₂M(WO₄)₂ (M = Co, Cu or Ni) cathode materials deliver initial discharge capacities of 31, 33 and 30 mA h g⁻¹ for cobalt, nickel, and copper, respectively.

Li₂M(WO₄)₂ (M = Co, Cu or Ni) materials have been synthesized using the solid-state reaction method.     

Comparison of nano-structured transition metal modified tri-metal MgMAl–LDHs (M = Fe,Zn, Cu,Ni, Co) prepared using co-precipitation

Comparison of layered double hydroxides (LDHs) synthesised using different methods, conditions and post-treatment is difficult to achieve because these greatly modify their material properties. This paper aims to provide a comparison of material properties for modified quintinite, where all LDHs were synthesised at the same conditions – thus allowing for direct comparison of the material properties obtained. Nano-structured materials were formed in all cases. The nano-structured transition metal (TM) MgMAl–LDHs were synthesised using constant pH co-precipitation. Five TMs (M = Fe, Co, Ni, Cu, Zn) were included in the LDH layers with molar substitutions of 0.5%, 1%, 5%, 10%, and 25% based on Mg-replacement for divalent TM cations and Al-replacement for trivalent TM cations. The materials were characterised using powder X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared analysis (ATR-FTIR), thermogravimetric analysis (TGA) and particle size analysis (PSA). The modified LDHs were synthesised free of major by-products and with similar morphologies. It could be shown that the crystallite dimensions varied between the different TM substitutions, that morphological changes were visible for some of the TMs used, that the processability depended on the TMs substituted, and that the substitution of TMs influenced the thermal stability of the LDHs.

Comparison of the effect of transition metal modification on the material properties of quintinite synthesised using co-precipitation under the same conditions.     

Theoretical study of ternary silver fluorides AgMF4 (M = Cu,Ni, Co) formation at pressures up to 20 GPa

Only several compounds bearing the Ag(ii) cation and other paramagnetic transition metal cations are known experimentally. Herein, we predict in silico stability and crystal structures of hypothetical ternary silver(ii) fluorides with copper, nickel and cobalt in 1 : 1 stoichiometry at a pressure range from 0 GPa up to 20 GPa employing the evolutionary algorithm in combination with DFT calculations. The calculations show that AgCoF₄ could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(i) and high-spin Co(iii). Although none of the compounds bearing Ag(ii) could be preferred over binary substrates at ambient conditions, at increased pressure ternary fluorides of Ag(ii) featuring Cu(ii) and Ni(ii) could be synthesized, in the pressure windows of 7–14 and 8–15 GPa, respectively. All title compounds would be semiconducting and demonstrate magnetic ordering. Compounds featuring Ni(ii) and particularly Co(ii) should exhibit fundamental band gaps much reduced with respect to pristine AgF₂. The presence of Cu(ii) and Ni(ii) does not lead to electronic doping to AgF₂ layers, while Co(ii) tends to reduce Ag(ii) entirely to Ag(i).

Only several compounds bearing the Ag(ii) cation and other paramagnetic transition metal cations are known experimentally. Here, we predict as yet unknown AgMF₄ phases and their stability in function of pressure.     

Fluorinated β-diketonate complexes M(tfac)2(TMEDA) (M = Fe,Ni, Cu,Zn) as precursors for the MOCVD growth of metal and metal oxide thin films

Partially fluorinated β-diketonate complexes M(tfac)₂(TMEDA) (M = Fe 1, Ni 2, Cu 3, Zn 4; tfac = 1,1,1-trifluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) were synthesized and structurally (sc-XRD) and thermochemically (TGA) characterised. A new polymorph of Fe(tfac)₂(TMEDA) was found. The structural and physicochemical properties of 1–4 were compared with related M(acac)₂(TMEDA) and M(hfac)₂(TMEDA) (acac = 2,4-pentanedionate, hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate) β-diketonate complexes to evaluate the effect of the degree of fluorination. A positive effect on the thermal behaviour of the metal acetylacetonates was observed, but no discernible trends. Application of complexes 1–4 as precursors in a MOCVD process yielded either metal (Ni, Cu) or metal oxide thin films (Fe₃O₄, ZnO), which were further oxidized to NiO, CuO and α-Fe₂O₃ films by calcination in air at 500 °C.

Novel trifluoroacetylacetonate complexes M(tfac)₂·TMEDA (M = Fe, Ni, Cu, Zn) were used as precursors for the MOCVD growth of metal and metal oxide thin films.     

Activation of peroxymonosulfate by metal (Fe,Mn, Cu and Ni) doping ordered mesoporous Co3O4 for the degradation of enrofloxacin

Various transition metals (Fe, Mn, Cu and Ni) were doped into ordered mesoporous Co₃O₄ to synthesize Co₃O₄-composite spinels. Their formation was evidenced by transmission electronic microscopy (TEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. It was found that Co₃O₄-composite spinels could efficiently activate peroxymonosulfate (PMS) to remove enrofloxacin (ENR) and the catalytic activity followed the order Co₃O₄–CuCo₂O₄ > Co₃O₄–CoMn₂O₄ > Co₃O₄–CoFe₂O₄ > Co₃O₄–NiCo₂O₄. Moreover, through the calculation of the specific apparent rate constant (k_sapp), it can be proved that the Co and Cu ions had the best synergistic effect for PMS activation. The Co₃O₄-composite spinels presented a wide pH range for the activation of PMS, but strong acidic and alkaline conditions were detrimental to ENR removal. Higher reaction temperature could promote the PMS activation process. Sulfate radical was identified as the dominating reactive species in Co₃O₄-composite spinel/PMS systems through radical quenching experiments. Meanwhile, the probable mechanisms concerning Co₃O₄-composite spinel activated PMS were proposed.

Various transition metals (Fe, Mn, Cu and Ni) were doped into ordered mesoporous Co₃O₄ to synthesize Co₃O₄-composite spinels.     

Syntheses,crystal structures,magnetic properties and ESI-MS studies of a series of trinuclear CuIIMIICuII compounds (M = Cu,Ni, Co,Fe, Mn,Zn)

Six trinuclear Cu^IIM^IICu^II compounds (M = Cu, Ni, Co, Fe, Mn, Zn) derived from the Schiff base ligand, H₂L (2 + 1 condensation product of salicylaldehyde and trans-1,2-diaminocyclohexane) are reported in this investigation. The composition of the metal complexes are [{Cu^IIL(ClO₄)}₂Cu^II(H₂O)]·2H₂O (1), [{Cu^IIL(ClO₄)}{Ni^II(H₂O)₂}{Cu^IIL}]ClO₄·CH₃COCH₃ (2), [{Cu^IIL(ClO₄)}{Co^II(CH₃COCH₃)(H₂O)}{Cu^IIL(CH₃COCH₃)}]ClO₄ (3) and isomorphic [{Cu^IIL(ClO₄)}₂M^II(CH₃OH)₂] (4, M = Fe; 5, M = Mn; 6, M = Zn). Two copper(ii) ions in 1–6 occupy N₂O₂ compartments of two L²⁻ ligands, while the second metal ion occupies the O(phenoxo)₄ site provided by the two ligands, i.e., the two metal ions in both Cu^IIM^II pairs are diphenoxo-bridged. Positive ESI-MS of 1–6 reveals some interesting features. Variable-temperature and variable-field magnetic studies reveal moderate or weak antiferromagnetic interactions in 1–6 with the following values of magnetic exchange integrals (H = −2JS₁S₂ type): J₁ = −136.50 cm⁻¹ and J = 0.00 for the Cu^IICu^IICu^II compound 1; J₁ = −22.16 cm⁻¹ and J = −1.97 cm⁻¹ for the Cu^IINi^IICu^II compound 2; J₁ = −14.78 cm⁻¹ and J = −1.86 cm⁻¹ for the Cu^IICo^IICu^II compound 3; J₁ = −6.35 cm⁻¹ and J = −1.17 cm⁻¹ for the Cu^IIFe^IICu^II compound 4; J₁ = −6.02 cm⁻¹ and J = −1.70 cm⁻¹ for the Cu^IIMn^IICu^II compound 5; J = −2.25 cm⁻¹ for the Cu^IIZn^IICu^II compound 6 (J is between two Cu^II in the N₂O₂ compartments; J₁ is between Cu^II and M^II through a diphenoxo bridge).

Six homo/heterotrinuclear Cu^IIM^IICu^II (M = Mn–Zn) compounds derived from salicylaldehyde-trans-1,2-diaminocyclohexane, which is a rarely utilized ligand, are reported.     

Facile preparation of rGO/MFe2O4 (M = Cu,Co, Ni) nanohybrids and its catalytic performance during the thermal decomposition of ammonium perchlorate

Reduced graphene oxide/metal ferrite (rGO/MFe₂O₄, M = Cu, Co, Ni) nanohybrids are successfully prepared through a simple, one-step hydrothermal method. The rGO/MFe₂O₄ nanohybrids are characterized by XRD, TEM, FT-IR, XPS, Raman and BET surface area measurements. The rGO/MFe₂O₄ nanohybrids demonstrate amazing catalytic activities on the thermal decomposition of ammonium perchlorate (AP). DSC results indicate that rGO/MFe₂O₄ nanohybrids (3 wt%), could decrease the decomposition temperature of pure AP from 424.7 °C to 329.1 °C, 338.3 °C, and 364.8 °C, respectively. This enhanced catalytic performance is mainly attributed to the synergistic effect of NPs and rGO. The activation energy (E_a) of AP mixed with nanohybrids is investigated by two isoconversion methods, Flynne–Walle–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS), on a conversion degree (α) range from 0.05 to 0.95. The values of E_a calculated from the above two methods matched with each other. A strong dependence of E_a on α is observed, indicating a complex decomposition process.

The rGO/MFe₂O₄ (M = Cu, Co, Ni) nanohybrids show amazing catalytic activity in the thermal decomposition process of AP.     

ZnO/MoX2 (X = S,Se) composites used for visible light photocatalysis

Hybrid density functional has been adopted to investigate the structural, electronic, and optical properties of ZnO/MoS₂ and ZnO/MoSe₂ composites as compared with the results of ZnO, MoS₂, and MoSe₂ monolayers. The results indicate that MoS₂ and MoSe₂ monolayers could contact with monolayer ZnO to form ZnO/MoS₂ and ZnO/MoSe₂ heterostructures through van der Waals (vdW) interactions. The calculated bandgap of ZnO/MoS₂ (ZnO/MoSe₂) is narrower than that of ZnO or MoS₂ (MoSe₂) monolayers, facilitating the shift of light absorption edges of the composites towards visible light in comparison with bare ZnO and MoX₂ monolayers. Through the application of strain, the ZnO/MoS₂ and ZnO/MoSe₂ composites which own suitable bandgaps, band edge positions, efficient charge separation, and good visible light absorption will be promising for visible light photocatalytic water splitting. These results provide a route for design and development of efficient ZnO/MoS₂ and ZnO/MoSe₂ photocatalysts for water splitting.

The ZnO/MoS₂ (ZnO/MoSe₂) heterostructures with the strain of –2% (+2%) have suitable bandgap and band edge position for hydrogen production via visible light photocatalytic water splitting.     

Peculiarities of the microwave properties of hard–soft functional composites SrTb0.01Tm0.01Fe11.98O19–AFe2O4 (A = Co,Ni, Zn,Cu, or Mn)

Herein, we investigated the correlation between the chemical composition, microstructure, and microwave properties of composites based on lightly Tb/Tm-doped Sr-hexaferrites (SrTb_0.01Tm_0.01Fe_11.98O₁₉) and spinel ferrites (AFe₂O₄, A = Co, Ni, Zn, Cu, or Mn), which were fabricated by a one-pot citrate sol–gel method. Powder XRD patterns of products confirmed the presence of pure hexaferrite and spinel phases. Microstructural analysis was performed based on SEM images. The average grain size for each phase in the prepared composites was calculated. Comprehensive investigations of dielectric properties (real (ε′) and imaginary parts (ε′′) of permittivity, dielectric loss tangent (tan(δ)), and AC conductivity) were performed in the 1–3 × 10⁶ Hz frequency range at 20–120 °C. Frequency dependency of microwave properties were investigated using the coaxial method in frequency range of 2–18 GHz. The non-linear behavior of the main microwave properties with a change in composition may be due to the influence of the soft magnetic phase. It was found that Mn- and Ni-spinel ferrites achieved the strongest electromagnetic absorption. This may be due to differences in the structures of the electron shell and the radii of the A-site ions in the spinel phase. It was discovered that the ionic polarization transformed into the dipole polarization.

Paper presents the correlation between the composition, microstructure, and microwave properties of composites based on Tb/Tm-doped Sr-hexaferrites and spinel ferrites (AFe₂O₄), which were fabricated by a one-pot citrate sol–gel method.     

Catalytic oxidation of ethyl acetate over LaBO3 (B = Co,Mn, Ni,Fe) perovskites supported silver catalysts

A series of silver catalysts supported on lanthanum based perovskites LaBO₃ (B = Co, Mn, Ni, Fe) were synthesized and evaluated in the catalytic oxidation of ethyl acetate. XRD, BET, TEM/HRTEM, HAADF-STEM, XPS and H₂-TPR were conducted, and the results indicate that redox activity of the catalysts is of great importance to the oxidation reaction. Activity tests demonstrated that Ag/LaCoO₃ was more active than the other samples in ethyl acetate oxidation. Moreover, the CO₂ selectivity, CO_x yields and byproduct distributions for all catalysts were studied, and Ag/LaCoO₃ showed the best catalytic performance. Besides, Ag/LaCoO₃ also showed excellent catalytic activity for other OVOCs.

Ag/LaBO₃ (B = Co, Mn, Ni, Fe) were investigated for the catalytic oxidation of ethyl acetate, and Ag/LaCoO₃ showed the best catalytic performance.     

Comparison of transition metal (Fe,Co, Ni,Cu, and Zn) containing tri-metal layered double hydroxides (LDHs) prepared by urea hydrolysis

This paper details a successful synthesis and comparison of a range of tri-metal hydrotalcite-like layered double hydroxides (LDHs) using urea hydrolysis. Transition-metal-substituted MgMAl-LDHs were synthesized with M = Fe, Co, Ni, Cu or Zn. 5 mol% and 10 mol% substitutions were performed, where Mg was substituted with Co, Ni, Cu and Zn, and Al with Fe. The successful synthesis of crystalline MgMAl-LDHs was confirmed using X-ray powder diffraction (XRD) analysis. Energy-dispersive X-ray (EDX) spectroscopy was used to identify substituted metals and determine changes in composition. Changes in morphology were studied using scanning electron microscopy (SEM). Thermogravimetric analysis was used to determine the effect of Fe-, Co-, Ni-, Cu- or Zn-substitution on the thermal degradation of the MgMAl-LDH phase. The structure, morphology and thermal behavior of the LDHs were shown to be influenced by the substituted transition metals. The observed thermal stability took the order MgNiAl- > MgFeAl- = MgAl- ≥ MgCoAl- > MgCuAl- > MgZnAl-LDH. The urea hydrolysis method was shown to be a simple preparation method for well-defined crystallite structures with large hexagonal platelets and good distribution of transition metal atoms in the substituted LDHs.

This paper details a successful synthesis and comparison of a range of tri-metal hydrotalcite-like layered double hydroxides (LDHs) using urea hydrolysis.     

Enhancement of NH3-SCR performance of LDH-based MMnAl (M = Cu,Ni, Co) oxide catalyst: influence of dopant M

Transition metal (Cu, Ni, Co) doped MnAl mixed oxide catalysts were prepared through a novel method involving the calcination of hydrotalcite precursors for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The effects of transition metal modification were confirmed by means of XRD, BET, TEM, XPS, NH₃-TPD, and H₂-TPR measurements. Experimental results evidenced that CoMnAl-LDO presented the highest NO_x removal efficiency of over 80% and a relatively high N₂ selectivity of over 88% in a broad working temperature range (150–300 °C) among all the samples studied. Moreover, the CoMnAl-LDO sample possessed better stability and excellent resistance to H₂O and SO₂. The reasons for such results could be associated with the good dispersion of Co₃O₄ and MnO_x, which could consequently provide optimum redox behavior, plentiful acid sites, and strong NO_x adsorption ability. Furthermore, dynamics calculations verified the meaningful reduction in apparent activation energy (E_a) for the CoMnAl-LDO sample, which is in agreement with the DeNO_x activity.

In situ doping of M (M = Cu, Ni, Co) into MnAl-LDH laminate to promote the NH₃-SCR performance of the MnAl-LDO catalyst.     

Efficient (Cu1−xAgx)2ZnSn(S,Se)4 solar cells on flexible Mo foils

Cation substitution plays a crucial role in improving the efficiency of Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells. In this work, we report a significant efficiency enhancement of flexible CZTSSe solar cells on Mo foils by partial substitution of Cu⁺ with Ag⁺. It is found that the band gap (E_g) of (Cu_1−xAg_x)₂ZnSn(S,Se)₄ (CAZTSSe) thin films can be adjusted by doping with Ag with x from 0 to 6%, and the minimum E_g is achieved with x = 5%. We also found that Ag doping can obviously increase the average grain size of the CAZTSSe absorber from 0.4 to 1.1 μm. Additionally, the depletion width (W_d) at the heterojunction interface of CAZTSSe/CdS is found to be improved. As a result, the open-circuit voltage deficit (V_oc,def) is gradually decreased, and the band tailing is suppressed. Benefiting from the enhanced open-circuit voltage (V_oc), the power conversion efficiency (PCE) is successfully enhanced from 4.34% (x = 0) to 6.24% (x = 4%), and the V_oc,def decreases from 915 to 848 mV.

Cation substitution plays a crucial role in improving the efficiency of Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells.     

Direct atomic absorption determination of the 3d elements (Fe, Cu, Mn, Co, Ni) and zinc in biological material

The authors' findings evidence the possibility of the blood serum, liver, spleen, and bone marrow Fe, Cu, Mn, Co, Ni, and Zn measurements by the direct atomic absorption method without their separation and extraction. The technique is simple, meets the requirements to physicochemical analyses, and may be recommended for investigations in theoretical and practical medicine. The method is not devoid of a number of drawbacks, that limit the range of its applications; this concerns, among other things, Co measurements. The studies have demonstrated significant differences in the levels of trace elements in the tested biological material, which is explained by the species and organic characteristics of their metabolism.     

Nb and Cu co-doped (La,Sr)(Co,Fe)O3: a stable electrode for solid oxide cells

Solid oxide cells (SOCs) are electrochemical devices that convert the chemical energy of a fuel into electricity. With regard to electrodes, the development of materials with mixed conduction properties is a key issue for improving the performance of SOCs at high temperatures. New Cu and Nb co-doping La_1−xSr_xFe_yCo_1−yO_3−δ (LSCF) materials were studied as electrode materials on yttria-stabilized zirconia (YSZ) supports. The results show that Cu_0.05 + Nb_0.05 co-doped LSCF maintains a stable cubic structure even after several heat treatments and has better conductivity than a classically used LSCF.

The stabilization of the cubic phase of LSCF co-substitution on the Fe site deposited on YSZ + GDC symmetrical cells to improve the performance.     

Nano ferrites (AFe2O4, A = Zn,Co, Mn,Cu) as efficient catalysts for catalytic ozonation of toluene

Nano ferrites (AFe₂O₄, A = Zn, Co, Mn, Cu) were supported on the surface of γ-Al₂O₃ support by hydrothermal synthesis to prepare a series of novel composite catalysts (AFe₂O₄/γ-Al₂O₃) for catalytic ozonation for elimination of high concentration toluene at ambient temperature. The characterization results showed that the high-purity nano-AFe₂O₄ particles were uniformly loaded on mesoporous γ-Al₂O₃. Further, it was confirmed that among the several catalysts prepared, the amount of oxygen vacancies (O_vs), Lewis acid sites (LAS), and Brønsted acid sites (BAS) of the ZnFe₂O₄/γ-Al₂O₃ catalyst were the highest. This meant that the ZnFe₂O₄/γ-Al₂O₃ catalyst had a strong adsorption capacity for toluene and ozone (O₃), and had a strong catalytic activity. When the temperature was 293 K and the space velocity was 1500 h⁻¹, the mol ratio of O₃ to toluene was 6, the degradation rate of toluene (600 mg m⁻³) can reach an optimum of 99.8%. The results of electron paramagnetic resonance (EPR) and Fourier infrared (FT-IR) proved superoxide radicals and hydroxyl radicals by catalytic ozonation. Moreover, the GC-MS analysis results indicated that the toluene degradation began with the oxidation of methyl groups on the benzene ring, eventually producing CO₂ and H₂O. After repeated experiments, the toluene degradation rate remained stable, and the residual content of O₃ in each litre of produced gas was less than 1 mg L⁻¹, thereby indicating that the ZnFe₂O₄/γ-Al₂O₃ catalyst had excellent reusability and showed great potential for the treatment of toluene waste gas.

Nano ferrites (AFe₂O₄, A = Zn, Co, Mn, Cu) were supported on the surface of γ-Al₂O₃ by hydrothermal synthesis to prepare a series of novel catalysts (AFe₂O₄/γ-Al₂O₃) for catalytic ozonation of high concentration toluene at ambient temperature.     

Recyclable MFe2O4 (M = Mn,Zn, Cu,Ni, Co) coupled micro–nano bubbles for simultaneous catalytic oxidation to remove NOx and SO2 in flue gas

NO_x can be efficiently removed by micro–nano bubbles coupling with Fe³⁺ and Mn²⁺, but the catalyst cannot be reused and the adsorption wastewater should be treated. This work developed a new technology that uses micro–nano bubbles and recyclable MFe₂O₄ to simultaneously remove NO_x and SO₂ from flue gas, and clarified the effectiveness and reaction mechanism. MFe₂O₄ (M = Mn, Zn, Cu, Ni and Co) prepared by a hydrothermal method was characterized. The results show that MFe₂O₄ can be activated to produce ˙OH which can accelerate the oxidation absorption of NO_x. Compared with no catalyst, the NO_x conversion rate increased from 32.85% to 83.88% in the NO_x–SO₂–MFe₂O₄-micro–nano bubble system, while the removal rate of SO₂ can reach 100% at room temperature. The catalytic activities of MFe₂O₄ showed the following trend: CuFe₂O₄ > ZnFe₂O₄ > MnFe₂O₄ > CoFe₂O₄ > NiFe₂O₄. The results provide a new idea for the application of advanced oxidation processes in flue gas treatment.

NO_x-SO₂-MFe₂O₄-micro–nano bubbles system for NO_x removal.     

Three-dimensional mesoporous PtM (M = Co,Cu, Ni) nanowire catalysts with high-performance towards methanol electro-oxidation reaction and oxygen reduction reaction

Alloying with transition elements is proven to be an effective way to improve the methanol electro-oxidation reaction (MOR) and oxygen reduction reaction (ORR) activities of Pt catalysts for direct methanol fuel cells (DMFCs). Through a process of rapid solidification and two-step dealloying, we have successfully fabricated three-dimensional mesoporous PtM (M = Co, Cu, Ni) nanowire catalysts, which show much enhanced electrocatalytic properties towards MOR and ORR in comparison with the commercial Pt/C catalyst. Electrochemical tests indicate that alloying with Cu presents the best ORR activities, the half-wave potential of which is 42 mV positively shifted compared with the commercial Pt/C (0.892 V vs. RHE). Meanwhile, the PtM nanowire catalysts also possess good CO tolerance as well as stability for 10 000 cycles of cyclic voltammetry scanning. This convenient preparation method is promising for the development of high performance electrocatalysts for MOR and ORR in DMFCs.

Alloying with transition elements is proven to be an effective way to improve the methanol electro-oxidation reaction (MOR) and oxygen reduction reaction (ORR) activities of Pt catalysts for direct methanol fuel cells (DMFCs).