Synthesis and Characterization of Cobalt and Nitrogen Co Doped Peat Derived Carbon Catalysts for Oxygen Reduction in Acidic Media

In this study, several peat derived carbons PDC were synthesized using various carbonization protocols. It was found that depending on the carbonization method, carbons with very different surface morphologies, elemental compositions, porosities, and oxygen reduction reaction ORR activities were obtained. Five carbons were used as carbon supports to synthesize Co N PDC catalysts, and five different ORR catalysts were acquired. The surface analysis revealed that a higher nitrogen content, number of surface oxide defects, and higher specific surface area lead to higher ORR activity of the Co N PDC catalysts in acidic solution. The catalyst Co N C 2 ZnCl2 , which was synthesized from ZnCl2 activated and pyrolyzed peat, showed the highest ORR activity in both rotating disk electrode and polymer electrolyte membrane fuel cell tests. A maximum power density value of 210 mW cm2 has been obtained. The results of this study indicate that PDCs are promising candidates for the synthesis of active non platinum group metal type catalyst

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Anion Effect of Zinc Source on Chemically Deposited ZnS(O,OH) Films

The study on the anion effect of different Zn sources—Zn(CH3COO)2, ZnCl2, ZnI2, Zn(NO3)2 and ZnSO4—on the chemical deposition of ZnS(O,OH) films revealed that the growth rate and composition of the ZnS(O,OH) layer depend on the instability constant (pK) value of the corresponding Zn-complex Zn(L)n in the chemical bath solution. In the region of pKZn(NH3)2+>pKZn(L)n the ZnS(O,OH) film's growth rate and ZnS concentration in films increased with the increasing pK value of the used Zn salt complex up to the pK value of the Zn[NH3]2+ complex and decreased in the region where pKZn(NH3)2+<pKZn(L)n. The band gap values (around 3.6 eV in most cases) of deposited ZnS(O,OH) films did not depend on the Zn precursor's instability constant, the ZnS(O,OH) film from zinc nitrate containing bath has higher band gap energy (Eg = 3.8 eV). The maximum efficiency of CISSe and CZTSSe monograin layer solar cells was gained with ZnS(O,OH) buffer layer deposited from CBD solution containing Zn(CH3COO)2 as Zn source, which provided the highest growth rate and ZnS concentration in the ZnS(O,OH) film on glass substrates

Effects of sulphur and tin disulphide vapour treatments of Cu2ZnSnS(Se)4 absorber materials for monograin solar cells

AbstractThe aim of this study was to find a heat-treatment procedure for monograin powders using a controllable reactive gas phase to improve the CZTS(Se) crystal surface for effectively working p-n junctions. The influence of an isothermal treatment in S and SnS2 vapour on the parameters of monograin layer solar cells is depending on the CZTS(Se) initial composition. The efficiencies of solar cells improve continuously with increasing temperatures of the absorber materials’ post-annealing from 823 to 973K under constant sulphur vapour pressure of 100 Torr. The highest values of Jsc= 18.4mA/cm2 and Voc= 720mV were obtained for a device made from CZTS powder annealed at 1013K in SnS2 vapour

Isothermal and Two-Temperature Zone Selenization of Mo Layers

Glass/Mo, Mo foil, glass/Mo/In, and glass/Mo/Cu stacked layers were selenized in closed vacuum tubes by isothermal and/or two-temperature zone annealing in Se vapors. The selenization process was studied dependent on Se vapor pressure, temperature and time. Samples were selenized from 375 to 580°C for 30 and 60 minutes. The applied Se pressure was varied between 130 and 4.4⋅103 Pa. The increase of MoSe2 film thickness was found to depend on the origin of Mo. MoSe2 thickness dL on Mo-foil was much higher than on sputtered Mo layers, and it depended linearly on time and as a power function dL~PSe1/2 on Se vapor pressure. The residual oxygen content in the formed MoSe2 layers was much lower in the two-zone selenization process. If Mo was covered with Cu or In before selenization, these were found to diffuse into formed MoSe2 layer. All the MoSe2 layers showed p-type conductivity

Exploring Different Synthesis Parameters for the Preparation of Metal Nitrogen Carbon Type Oxygen Reduction Catalysts

The influence of various synthesis conditions of a metal nitrogen carbon M N C catalyst material on oxygen reduction reaction ORR kinetics is discussed. Seven M N C catalysts based on cobalt are obtained by changing various synthesis conditions, such as the mixing environment, pyrolysis gas, and post treatment. The ORR activity and stability measurements are performed using the classical three electrode configuration in a 0.1 M HClO4 solution. The most active and stable ORR catalyst proves to be the material obtained by mixing a cobalt salt, 2,2 bipyridine, and a high surface area silicon carbide derived carbon together in water and pyrolyzing the mixture in argon. In a fuel cell test, however, a maximum power density value of 135 mW cm amp; 8722;2 is achieved with the catalyst mixed together in a planetary ball mill at a low catalyst loading of 1.0 0.1 mg cm amp; 8722;2 and at a test cell temperature of 60 oC despite of the fact that preparing the catalyst via dry ball milling reduces the surface area of the material roughly 40 more than in the case of using a solution based method. Consequently, mixing the catalyst precursors together without any additional chemicals in a planetary ball mill instead of in a solution appears to be the most promising choic

Peat derived carbon based non platinum group metal type catalyst for oxygen reduction and evolution reactions

For the first time, a novel peat derived carbon PDC was used to synthesize an active non platinum group metal type catalyst for the oxygen reduction reaction ORR and oxygen evolution reaction OER . The obtained catalyst exhibited a smaller specific surface area and was more graphitic compared to a catalyst synthesized identically but using carbide derived carbon CDC instead of PDC. Due to the organic nature of the used peat, the PDC contained numerous additives. In 0.1 M KOH, both the PDC and CDC based catalysts displayed ORR activity comparable to Pt Vulcan. Additionally, equally high OER activities of 1.59 V vs RHE at 10 mA cm amp; 8722;2 were reached for both catalysts studied. Considering the remarkable bifunctional activity of the PDC based catalyst, it can be concluded that PDC is an exceptionally promising carbon support material for ORR and OER catalyst

Cobalt and Nitrogen Co Doped Peat Derived Carbon Based Catalysts for Oxygen Reduction

Using different carbonization protocols, five peat derived carbon materials were synthesized. These carbons have very different surface morphology confirmed by HR SEM and different porosities and pore size distributions obtained by N2 sorption method. The ORR activity of the peat derived carbons also differs significantly in 0.1 M HClO4 solution. Additionally, co doping the peat derived carbons with cobalt and nitrogen enhanced their catalytic activity considerably. The most active ORR catalyst was achieved using the carbon support where the dry milled peat was mixed with ZnCl2 and pyrolyzed in Ar for 2 h at 700 C. Interestingly, the activity of the initial carbon powder does not seem to be a clear indicator of the final activity of the M N C catalysts synthesized from i