Investigation Of Anode Materials For Intermediate Temperature H₂S Solid Oxide Fuel Cells

Based on the development of higher temperature H2S Solid Oxide Fuel Cells (SOFC), in order to overcome the shortcoming of the materials under the condition of higher temperature and in H2S, the paper was focused on anode materials for intermediate temperature H2S SOFC by experiments and analysis of thermodynamic calculation. The preparations of sevrial anode and the properties of them in H2S were studied. After building single cells which electrolytes as surppoted, the tested electrochemical properties were used to find out a more suitable anode for intermediate temperature H2S SOFC.Urea combustion method was used to prepare a series of La0.7Sr0.3Cr1-xYx03-δ (abbreviation:LSCY). The measurements of X-ray diffraction (XRD), conductivities in H2S and H2-temperature programmed reduction (H2-TPR) were used to determine the optimum sintering temperature1350℃and the favourable doping quantity x=0.13. The maximum OCV was0.85V and the maximum power density was12.42mW·cm-2for the single cell LSCY13-SDC‖SDC‖Ag in5%H2S at600℃. The results of X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) after the cell test showed that La was replaced by Sr to produce oxygen vacancies which had no charge, and the oxygen vacancies provided channel for migrating of O2-, which enlarged area of reaction H2S with O2-. The appearance of delocalized d electron after Y doping enhanced the conduction of the anode material.Gel combustion method was used to synthesize Ce0.9Sr0.1Cr0.5Co0.5O4-δ (CSCCo) precursor, then reduced in3%H2at1100℃to get fluorite of CSCCo anode powder. The results of XRD, H2-TPR and FT-IR, et al. showed that CSCCo was suit for as anode for intermediate temperature H2S SOFC. The maximum OCV was0.97V and the maximum power density was14.21mW·cm-2for the single cell CSCCo-SDC‖SDC‖Ag in5%H2S at600℃. Due to the electron easily transfering from Ce3+to Co3+, the hoping elentron increased the electron conductivity of the material; meanwhile Sr doping producing oxygen vacancies was in favour of enhancing the electrochemical properties for intermediate temperature H2S SOFC.Ce0.9Sr0.1Cr0.5Mn0.5O4-δ (CSCMn) precursor was synthesized by gel combustion method, after reduction in3%H2, the fluorite of CSCMn anode powder was abtained. The analysis of XRD、H2-TPR and conductiviyies in H2S made sure CSCMn fitting as anode for intermediate temperature H2S SOFC. The maximum OCV was0.95V and the maximum power density was15.12mW·cm-2for the single cell CSCMn-SDC‖SDC‖Ag in5%H2S at600℃. After the single cell test, XPS patterns showed that electron transferred from Ce3+to Mn4+which enhanced the conduction of the anode material. Lattice oxygen on the surface of the anode was changed to interstitial atom of oxygen and letted out oxygen vacancies, which magnified the area of touching for H2S and O2-.Gel combustion method was used to synthesize Ce0.9Sr0.1Cr0.5Fe0.5O3-δ(CSCFe) precursor powder, perovskite CSCFe and fluorite type CSCFe were gotten after the reducrion in3%H2or in100%H2at1100℃for5h. XRD, H2-TPR and FT-IR were used to certain both CSCFe all suiting as anodes for intermediate temperature of H2S SOFC, and the single with them as anode, the maximum current densities were52.35mA·cm-2and82.38mA·cm-2, the maximum power densities were17.75mW·cm-2and18.75mW·cm-2for the cell CSCFe-SDC‖SDC‖Ag in5%H2S at600℃, respectively. The reason may be the difference from content of Ce3+in CSCFe; Ce3+in the former (30.35%) was less than the latter (70.26%).Model of the cell was proton conducting electrolyte BaCe0.35Zr0.5Y0.15O3-δ as supported. Amorphous structure BaCe0.35Zr0.5Y0.15O3-Li3PO4-CaSO4(BCZY-Li-Ca) and perovskite structure Ce0.8Sr0.2Cr0.5V0.5O3-δ(CSCV) as anode, the electrochemical propteries were carried out for the single cells BCZY-Li-Ca-BCZY‖BCZY‖Ag and CSCV8255-BCZY‖BCZY‖Ag in5%H2S at600℃, the maximum OCVs were0.81V and0.99V, the maximum power densities were13.1mW·cm-2and22.6mW·cm-2, respectively. The activity of fomer was lower than that of the former, the reason was that CSCV and BCZY were all perovskite and all contained Ce, which made magnify the chemical compatibility and reduced the contacting resisitance between them.