The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination te...A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co(10∶90)/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co(10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis(EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10∶90)/Al2O3 catalyst.展开更多
【目的】探究不同水稻品种对稻田温室气体排放的影响,以期筛选出适宜重庆地区种植的高产、温室气体低排放水稻品种。【方法】通过田间试验,采用静态箱—气相色谱法连续观测重庆地区主推的6个水稻品种(中浙优H7、渝两优华占、Q香优352、...【目的】探究不同水稻品种对稻田温室气体排放的影响,以期筛选出适宜重庆地区种植的高产、温室气体低排放水稻品种。【方法】通过田间试验,采用静态箱—气相色谱法连续观测重庆地区主推的6个水稻品种(中浙优H7、渝两优华占、Q香优352、神农优446、渝香优8133、渝香203)甲烷(CH_(4))和氧化亚氮(N_(2)O)排放通量,收获期测定水稻产量,并对比其全球增温潜势和温室气体排放强度。【结果】在6个水稻品种中,仅中浙优H7的CH_(4)排放通量呈双峰趋势,峰值分别出现在抽穗期—灌浆期和成熟期—收获期;其余5个品种的CH_(4)排放通量均呈单峰趋势,且峰值均出现在抽穗期—灌浆期。不同品种的CH_(4)排放总量为175.77~274.10 kg/ha,其中,Q香优352的CH_(4)排放总量最低,而渝香优8133排放总量最高,二者间存在显著差异(P<0.05,下同)。N_(2)O的明显排放峰出现在稻田落干后,排放总量为-0.100~0.464 kg/ha,各品种间的N_(2)O排放总量无显著差异(P>0.05),其中渝香优8133的N_(2)O排放总量为负值。不同品种水稻产量为4.94~8.20 t/ha,其中Q香优352产量最高,渝两优华占产量最低,二者间存在显著差异。全球增温潜势分析显示,中浙优H7的全球增温潜势最高,达7.67 t CO_(2)e/ha,而Q香优352的全球增温潜势最低,为4.98 t CO_(2)e/ha。不同水稻品种的温室气体排放强度在0.61~1.54 t CO_(2)e/t,其中Q香优352的温室气体排放强度最低,显著低于其他品种,而中浙优H7的温室气体排放强度最高。【结论】综合考虑产量和温室气体排放情况,Q香优352产量最高,且CH_(4)排放总量和温室气体排放强度最低,更适宜在重庆及类似地区推广种植。展开更多
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
文摘A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co(10∶90)/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co(10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis(EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10∶90)/Al2O3 catalyst.
文摘【目的】探究不同水稻品种对稻田温室气体排放的影响,以期筛选出适宜重庆地区种植的高产、温室气体低排放水稻品种。【方法】通过田间试验,采用静态箱—气相色谱法连续观测重庆地区主推的6个水稻品种(中浙优H7、渝两优华占、Q香优352、神农优446、渝香优8133、渝香203)甲烷(CH_(4))和氧化亚氮(N_(2)O)排放通量,收获期测定水稻产量,并对比其全球增温潜势和温室气体排放强度。【结果】在6个水稻品种中,仅中浙优H7的CH_(4)排放通量呈双峰趋势,峰值分别出现在抽穗期—灌浆期和成熟期—收获期;其余5个品种的CH_(4)排放通量均呈单峰趋势,且峰值均出现在抽穗期—灌浆期。不同品种的CH_(4)排放总量为175.77~274.10 kg/ha,其中,Q香优352的CH_(4)排放总量最低,而渝香优8133排放总量最高,二者间存在显著差异(P<0.05,下同)。N_(2)O的明显排放峰出现在稻田落干后,排放总量为-0.100~0.464 kg/ha,各品种间的N_(2)O排放总量无显著差异(P>0.05),其中渝香优8133的N_(2)O排放总量为负值。不同品种水稻产量为4.94~8.20 t/ha,其中Q香优352产量最高,渝两优华占产量最低,二者间存在显著差异。全球增温潜势分析显示,中浙优H7的全球增温潜势最高,达7.67 t CO_(2)e/ha,而Q香优352的全球增温潜势最低,为4.98 t CO_(2)e/ha。不同水稻品种的温室气体排放强度在0.61~1.54 t CO_(2)e/t,其中Q香优352的温室气体排放强度最低,显著低于其他品种,而中浙优H7的温室气体排放强度最高。【结论】综合考虑产量和温室气体排放情况,Q香优352产量最高,且CH_(4)排放总量和温室气体排放强度最低,更适宜在重庆及类似地区推广种植。
