Addition Of Second Metal Research Articles

Metal-oxide catalysts for CO TOX and PROX processes in the Pt–Cr/Mo/W systems

The properties of Pt-based catalysts could be modified by the addition of second metal and formation of an alloy or metal-oxide interface. In the present work we studied the effect of Cr, Mo and W doping on the Pt performance in CO TOX and PROX reactions. [Pt(NH3)4]MO4 (M = Mo, W) salts and solid solutions [Pt(NH3)4](M’O4)x(M″O4)1-x (M’ = Cr,Mo,W; M’‘ = Cr,Mo,W) were used as a single-source catalyst precursors. They were synthesized and characterized by a number of physicochemical methods of analysis. The thermal properties of obtained salts were studied in an oxidative atmosphere. The process of the decomposition is multistage and ends with a formation of platinum and the corresponding oxides of base metals (Cr/Mo/W).

Enhanced removal of antibiotic resistance genes by nanoscale iron-cobalt particles modified with Ginkgo biloba L. leaf: Combining Illumina MiSeq sequencing and oligotyping analysis

The addition of second metal (Co) to nanoscale iron particles (NIPs) is an attractive strategy to improve catalytic capacity. However, the nanoparticles tend to form chain-like aggregates. In this study, bacterial 16S rRNA gene, antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) from secondary effluent were significantly removed by Ginkgo biloba L. modified nanoscale iron-cobalt particles (GNICPs). When the Co loading, initial pH value, DO and dosage were 10%, 7.33, 8.94 mg/L and 1.12 g/L, some ARGs and MGEs could be reduced below the detection limit at the 2nd or 3rd cycle. Illumina MiSeq sequencing demonstrated that negative correlations were found between ARGs and reaction time/cycles. The predicted microbial functions by FAPROTAX database indicated GNICPs were effective in eliminating human_pathogens_all. Furthermore, oligotyping revealed all ARGs and MGEs were positively correlated with oligotype 10, which indicated GNICPs removed oligotype 10 easily.

Comparative Study of the ORR Activity and Stability of Pt and PtM (M = Ni, Co, Cr, Pd) Supported on Polyaniline/Carbon Nanotubes in a PEM Fuel Cell.

The oxygen reduction reaction (ORR) activity and stability of platinum (Pt) and PtM (M = Ni, Co, Cr, Pd) supported on polyaniline/carbon nanotube (PtM/PANI-CNT) were explored and compared with the commercial Pt/C catalyst (ETEK). The Pt/PANI-CNT catalyst exhibited higher ORR activity and stability than the commercial Pt/C catalyst even though it had larger crystallite/particle sizes, lower catalyst dispersion and lower electrochemical surface area (ESA), probably because of its high electrical conductivity. The addition of second metal (M) enhanced the ORR activity and stability of the Pt/PANI-CNT catalyst, because the added M induced the formation of a PtM alloy and shifted the d-band center to downfield, leading to a weak chemical interaction between oxygenated species and the catalyst surface and, therefore, affected positively the catalytic activity. Among all the tested M, the addition of Cr was optimal. Although it improved the ORR activity of the Pt/PANI-CNT catalyst slightly less than that of Pd (around 4.98%) in low temperature (60 °C)/pressure (1 atm abs), it reduced the ESA loss by around 14.8% after 1000 cycles of repetitive cyclic voltammetry (CV). In addition, it is cheaper than Pd metal. Thus, Cr was recommended as the second metal to alloy with Pt on the PANI-CNT support.

Bimetallic platinum group metal-free catalysts for high power generating microbial fuel cells

M1-M2-N-C bimetallic catalysts with M1 as Fe and Co and M2 as Fe, Co, Ni and Mn were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR). The catalysts were prepared by Sacrificial Support Method in which silica was the template and aminoantipyrine (AAPyr) was the organic precursor. The electro-catalytic properties of these catalysts were investigated by using rotating ring disk (RRDE) electrode setup in neutral electrolyte. Fe-Mn-AAPyr outperformed Fe-AAPyr that showed higher performances compared to Fe-Co-AAPyr and Fe-Ni-AAPyr in terms of half-wave potential. In parallel, Fe-Co-AAPyr, Co-Mn-AAPyr and Co-Ni-AAPyr outperformed Co-AAPyr. The presence of Co within the catalyst contributed to high peroxide production not desired for efficient ORR. The catalytic capability of the catalysts integrated in air-breathing cathode was also verified. It was found that Co-based catalysts showed an improvement in performance by the addition of second metal compared to simple Co- AAPyr. Fe-based bimetallic materials didn't show improvement compared to Fe-AAPyr with the exception of Fe-Mn-AAPyr catalyst that had the highest performance recorded in this study with maximum power density of 221.8 ± 6.6 μWcm−2. Activated carbon (AC) was used as control and had the lowest performances in RRDE and achieved only 95.6 ± 5.8 μWcm−2 when tested in MFC.

Influence of Foreign Metal Dopants on the Durability and Performance of Zr/Ca Sorbents during High Temperature CO2 Capture

The effect of foreign metal on the adsorption performance and stability of the Zr/Ca sorbents has been investigated for high temperature CO2 capture. For this purpose, M/Zr/Ca (M˭Al, W, Hf, Ce, and Y) sorbents are prepared by the flame spray pyrolysis method with the molar ratio 0.5:0.5:10. Improvement in the stability and sorption capacity were observed in Zr/Ca sorbents after doping with some foreign metals. The Al-doped Zr/Ca sorbent (Al/Zr/Ca) with the molar ratio of 0.5:0.5:10 exhibits excellent performance and remarkable stability among all the sorbents tested. The sorbent was stable up to about 50 carbonation-decarbonation cycles due to its high resistance towards sintering. The sorbent shows CO2 capture capacity of 0.54 g/g which is comparable to Zr/Ca (1/10) sorbent (0.53 g/g). Surface area measurements show that addition of a second metal to the Zr/Ca sorbents greatly influences both the surface area and pore volume of the sorbents. Our TPD results indicate that addition of second metal lowers the decarbonation temperature. XRD results show that the improved resistance of the Al/Zr/Ca (0.5/0.5/10) sorbent was attributed to the formation of structures like CaZrO3 and Ca12Al14O33, which provided a stable framework to the sorbent during the adsorption process.

Synthesis and characterization of bimetallic nanocatalysts and their application in selective hydrogenation of citral to unsaturated alcohols

TiO2-supported bimetallic nanocatalysts were prepared and reduced at two different temperatures, 375°C and 575°C for selective hydrogenation of citral to corresponding unsaturated alcohols (geraniol (GOL) and nerol (NOL)). The nanocatalysts were characterized by difference techniques of Fourier transform infrared spectroscopy (FT-IR), Brunauer, Emmett and Teller (BET) surface area measurement, scanning electron microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared nanocatalysts are uniformly dispersed with an average particle size of 50–100 nm and zero valence metallic state. Catalysts reduced at higher temperature lead to an increase in selectivity toward unsaturated alcohols (GOL and NOL). The Pt–Ru/TiO2 shows higher activity compared to Pt–Pd/TiO2 and Pt–Au/TiO2 nanocatalysts. In addition, a second metal (Ru) also leads to an increase in GOL and NOL selectivity during citral hydrogenation. Partially generated oxidized second metal species due to the difference in electronegativity, strongly binds the C=O group and also paves the way for selective activation of C=O bond. The Pt-Ru/TiO2 nanocatalyst reduced at higher temperature leads to an increase in selectivity toward unsaturated alcohols (GOL and NOL). The addition of second metal (Ru) generates partial positive charge on Ru centre due to the difference in electronegativity, which strongly binds C=O group and paves way for the selective activation of the C=O bond.

Performance studies of copper–iron/ceria–yttria stabilized zirconia anode for electro-oxidation of butane in solid oxide fuel cells

Addition of second metal to Cu is useful for electro-oxidation of hydrocarbons in solid oxide fuel cells (SOFC). In this work, electro-catalysts based on Cu–Fe bimetallic anode for use of both H2 and n-C4H10 in SOFC is prepared by wet impregnation method into a porous CeO2–YSZ matrix. The prepared Cu–Fe/CeO2–YSZ anodes are then characterized by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), elemental dispersive X-ray (EDX) and scanning electron microscopy (SEM). Carbonaceous deposits formed on Cu–Fe/CeO2–YSZ anodes after exposure to n-C4H10 are studied using a combination of i–V characteristics and TGA measurements. It is observed that the addition of Fe to Cu in CeO2–YSZ cermet anode enhance the performance in H2 and n-C4H10 fuels. The performance of cell having molar ratio of Cu–Fe of 1:1 in Cu–Fe/CeO2–YSZ anode shows power density of 240 mW cm−2 and 260 mW cm−2 in n-C4H10 and in H2 after n-C4H10 flow at 800 °C. The i–V curve shows that the conductivity of the anode improves after exposure to n-C4H10. No apparent degradation in performance is observed after n-C4H10 flow except for carbon fibre formation indicating Cu–Fe bimetallic is worth considering as an anode for direct butane SOFC.

Selective hydrogenolysis of dichlorodifluoromethane (CCl 2F 2) over CCA supported palladium bimetallic catalysts

La, Bi, Sb, Sn, Ba, and Zn are chosen for addition on carbon covered alumina (CCA) supported Pd catalyst. The effect of these second metals on supported Pd catalysts has been studied for the hydrogenolysis activity of CCl 2F 2. Bi and Sb promoters have been found to improve not only the thermal stability but also selectivity towards CH 2F 2. Sn bimetallic catalyst exhibited high selectivity towards CHClF 2. This may be explained on the basis of the metal–metal interactions that influence the reducibility of the palladium. These improved properties arise due to inter-metallic compound formation as evidenced from the XRD and TPR data on CCA supported bimetallic palladium catalysts. The effect of addition of second metal on Pd/CCA catalyst is screened in terms of partial dehalogenation ability and thermal stability for hydrodechlorination activity of CCl 2F 2 to maximize the CH 2F 2 yield.