The cell with the LSCF air electrode showed better performance than the LSM cell in both fuel cell and electrolysis operation modes and for all the gas compositions investigated (see Fig. 2 and Table 1). In particular, the ASR of cell A at 800 °C 50/50 H2/H2O was about 1.6 times lower than that of cell B in both SOFC/SOEC modes, and still lower than the ASR of cell B test at 850 °C. The SOFC and SOEC polarizations of the LSM cell were almost symmetric with both investigated fuel mixtures, while the LSCF cell showed higher losses in the electrolysis mode at high current density. This is in agreement with the literature that reports asymmetric polarizations for LSCF electrodes . This behavior can be attributed to the depletion of oxygen vacancies at the electrode/electrolyte interface that occurs under SOEC mode. The air electrode shows a limiting current behavior under anodic polarization because the oxygen transport is slowed down by the depletion of vacancies; this YPYDVPDYA effect is evident in highly oxygen deficient materials, as LSCF above 600 °C, while is less discernible for LSM that has an ionic conductivity of several orders of magnitude lower than LSCF  and . At a current density of 0.5 A cm−2 (RU ∼70%) the 50/50 H2/H2O test on cell A showed a difference of 34 mV between SOEC and SOFC total overpotential against only 2 mV of cell B in the same operating conditions. It must be emphasized that the effect of the back-flow diffusion can favor SOEC operation by generating new reactant at the cell border; therefore with a sealed-housing testing rig it could be expected an even worse behavior of the cells in SOEC at high RU. In Fig. 4 is highlighted the asymmetrical behavior of the LSCF cell, which had lower total cell resistance in SOFC mode at all the tested RUs. The increase of the total cell resistance observed in Fig. 4 in both operational modes with increasing RU is due to enhanced conversion resistance (low frequency arcs are connected to fuel conversion phenomena ).
Product yields of slow pyrolysis of rice straw at different temperatures.Temperature, °CBio-oil, wt.%Bio-char, wt.%Gas, wt.%Conversion, %30029.239.231.660.835030.635.633.864.44003134.234.865.845029.833.23766.8Full-size tableTable optionsView in workspaceDownload as CSV
Between the temperatures of 400 and 450 °C, the yield of gas has increased thereby reducing the bio-oil yield since the bio-char yield 3X FLAG tag almost similar. The secondary reactions are supposed to have occurred thereby producing non-condensable gases. The decrease in the char yield with increasing temperature could either be due to greater primary decomposition of biomass at higher temperatures or through secondary decomposition of char residue (Pütün et al., 2005). It can be concluded that 400 °C is the optimum temperature for slow pyrolysis of rice straw giving high yields of desirable products namely the bio-oil and bio-char. The results are well in line with that observed in the open literature as the bio-oil yield is more in case of inert atmosphere than hydrogen atmosphere. This maybe due to the tendency to produce more vapours which re-polymerise into char in case of reductive gas presence (Thangalazhy-Gopakumar et al., 2011).
2.5. Characterization of ZM and PANI nanoparticles and PANI/ZM nanocomposite
X-ray diffraction (XRD) patterns of MA treated ZM, PANI and PANI/ZM nanocomposite was recorded by using powder X-ray diffractometer (Rigaku Mini-Flox, USA). FTIR analysis of samples was also obtained using a SHIMADZU 8400S FTIR spectrometer in KBr medium at room temperature in the region of 4000–500 cm−1. The morphology of MA treated ZM, PANI and PANI/ZM nanocomposite was investigated by using Transmission Electron Microscopy (TEM), (PHILIPS, CM200, 20–200 kV, magnification 1,000,000×). The weight loss of PANI and PANI/ZM nanocomposite was determined in the range of room temperature to 700 °C by using a thermogravimetric analysis (PerkinElmer TGA system, USA), in an N2 EPZ-6438 at a heating rate of 10 °C/min.
2.6. Property evaluation of PANI/alkyd and PANI/ZM nanocomposite/alkyd coatings
Mechanical property such as cross-cut adhesion was evaluated as per ASTM standards. Corrosion tests were carried out in acid, alkali, and salt solution (5 wt.% each) by placing the MS strips in beakers and coated samples were immersed in corrosion media till corrosion occurred and cracks were developed. Each sample was exposed to corrosion media approximately for 200 h. The corrosion rate (VC) for each samples  was estimated by using the expression (1):equation(1)VC=ΔgAtdwhere Δg is the weight loss in grams for each sample, A is the exposed area of the sample in mm2, t is the time of exposure in years, and d is the density of the metallic species in g/mm3. The weight loss of test sample was considered after cautiously washing the MS plates with deionized water till the deposited corrosion product was removed and then moisture was removed from the samples by drying at 60 °C (±1) in an oven.
3.2. Electrocatalytic characteristics of Cu/AC cathode
Fig. 3. (a) Nyquist plots of EIS by bare AC and Cu/AC air cathodes. Lines marked as ‘Cal’ were fitting data from AF 12198 equivalent circuit. (b) Tafel plots of different air–cathode.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fitting results of different cathodes based on the equivalent circuit.Raw-ACAC/CuR0 (Ω)15.659.112Cdl (10−7 Ω−1 sn cm−2)0.30660.1707ndf0.67070.8602Rd (Ω)0.53120.3013W (Ω S−1/2)1.31920.3385Cad (Ω−1 sn cm−2)0.001250.00078nad0.66140.6707Rct (Ω)9.3981.381Full-size tableTable optionsView in workspaceDownload as CSV
3.3. Characterization of Cu2O
The morphologies for raw-AC and Cu/AC cathodes are given in Fig. S2. The activated carbon showed the random pore size distribution and interconnected pore systems. Also, the tight and brawny PTFE fibers were present in the AC granules. However, the morphology of the Cu2O coated activated carbon was ribbon-like and respiratory surface was totally different from the bare activated carbon. Interconnected ribbons with submicrometer scale on the AC surface could be clearly observed. Compared with the reported Cu2O cubes, Cu2O balls (Yan et al., 2012) and Cu2O stars (Grez et al., 2012), these ribbon-like Cu2O was firstly observed and the deposited-Cu2O ribbons on AC could increase the roughness of the AC, resulting more activated sites for ORR.
Fig. 1. Enzymatic hydrolysis of the best alkali-treated cotton gin substrates at different total solids (%) and enzyme loadings (mg g−1 ss): cotton gin dust (A) and cotton gin waste (B).Figure optionsDownload full-size imageDownload as PowerPoint slide
The results obtained after 24 and 92 h of hydrolysis under different experimental conditions are shown in Table 5 and these are presented as conversion (%) in relation to the substrate glucan content and as the corresponding BMY 14802 concentration (g L−1) in the substrate hydrolysate. Since these values were statistically different for different pretreatment conditions (p < 0.05 in the ANOVA), the Tukey’s test was used to identify which of the individual responses were different from one another.
The largest glucan conversion after 24 h was obtained with the lowest substrate total solids (5 wt%) and the highest enzyme loading (11.5 FPU g−1 of dry substrate), as demonstrated by CGD-2 and CGW-7 in Table 5. These experiments resulted in 40.8 ± 1.0 and 36.5 ± 0.9% of glucan conversion, respectively, and these values were statistically different (p < 0.05) when compared to all other hydrolysis conditions. However, the highest concentration of fermentable sugars was obtained at 15 wt% total solids with 11.5 FPU g−1 of dry substrate (or 85 mg of enzyme g−1) for both pretreated materials, being 24.1 ± 0.4 g L−1 of glucose for CGD-1 and 22.9 ± 0.8 g L−1 of glucose for CGW-6.
3.4. Minimum oxygen requirements
To test whether providing one pore volume of air was sufficient for the long term operation and acetate removal, the reactor was run continuously for 24 cycles. Over 80 h it was demonstrated that 14 Cmmol/L acetate (448 mg/L BOD) present in the synthetic wastewater were removed in cycles of 3.5 h (Fig. 6). Therefore the removal rate of acetate was 4 Cmmol/L/h (123 mg/L/h BOD), which is a carbon removal rate that is about 3 times higher than typically observed in activated sludge plants (Tandukar et al., 2007). No significant Embelin output was recorded over this time. From the reproducible oxygen uptake curves (data not shown) sickle cell anemia could be predicted that approximately 50% of the acetate added was respired (Table 2).
Fig. 6. The effect of increasing the carbon to oxygen ratio, on the continuous removal of acetate. Continuous operation of the storage biofilm reactor under repeated cycles of synthetic wastewater with 1 pore volume of air provided, 24 cycles of 14 Cmmol/L, 18 cycles of 22 Cmmol/L and 5 cycles of 30 Cmmol/L. Example cycles of 14 Cmmol/L (●) and carbon outflow (○), of 22 Cmmol/L (?) and carbon outflow (△), and of 30 Cmmol/L (■) and carbon outflow (□).Figure optionsDownload full-size imageDownload as PowerPoint slide