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揭示明确定义的金属-N_(4)位点在电催化硝酸盐还原中的活性趋势
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作者 蒋远 杨级 +5 位作者 李沐霖 王雪佳 杨娜 陈伟平 董金超 李剑锋 《Chinese Journal of Catalysis》 SCIE CAS CSCD 2024年第4期195-203,共9页
氨是一种重要的化工原材料,广泛用于肥料、药物、塑料以及其它化工产品的生产.特别是,氨作为一种绿色、新型的替代燃料,正逐渐被视为未来可持续能源体系的重要组成部分之一.近期,研究者们提出了一种新的等离子体电催化合成氨的方法,为... 氨是一种重要的化工原材料,广泛用于肥料、药物、塑料以及其它化工产品的生产.特别是,氨作为一种绿色、新型的替代燃料,正逐渐被视为未来可持续能源体系的重要组成部分之一.近期,研究者们提出了一种新的等离子体电催化合成氨的方法,为氨的生产开辟了新的途径.该方法首先在等离子处理条件下将空气中的氮气和氧气氧化成为氮氧化物;然后,通过电催化还原NOx-(主要为NO_(2)-/NO3-等)合成氨.在该过程中,金属-氮-碳单原子(M-N-C SACs)催化剂因其金属原子利用率高、活性和选择性好等优点而受到广泛关注.然而,由于当前催化剂合成路线的可控性不足,导致金属中心的配位环境复杂,MNx配位数(x=2-5)不明确,阻碍了对催化剂本征活性趋势的深入揭示.为了解决上述问题,研究者们开始关注具有均匀且明确MN_(4)结构的金属酞菁(MPc),并将其作为模型催化剂,用于深入研究电催化硝酸盐还原反应的活性位点和反应机理.本文将六种具有明确MN_(4)结构的金属酞菁催化剂(M=Mn,Fe,Co,Ni,Cu和Zn)负载在卡博特碳黑XC-72R载体上,并探究了不同金属中心的MN_(4)位点对硝酸盐还原合成氨的活性影响.扫描电子显微镜、X射线光电子能谱以及氮气吸脱附等温曲线结果表明,六种不同金属中心的MPc/XC-72R催化剂间的差异仅在于金属中心,从而排除了载体等其他因素的干扰.实验结果显示,金属中心对硝酸盐还原合成氨的活性顺序为:FeN_(4)>CuN_(4)>NiN_(4)>MnN_(4)>CoN_(4)>ZnN_(4).其中,FeN_(4)位点表现出最好的催化活性,在-1.0 V vs.RHE时,氨的法拉第效率达到83.3%,产率为2.94 mgNH3 h^(-1)cm^(-2),转化频率(TOF)为4395.2 h^(-1).相比之下,在相同条件下,ZnN_(4)位点上亚硝酸盐的选择性和产率最高,亚硝酸盐的法拉第效率为49.1%,产率达到16.8 mgNO_(2)h^(-1)cm^(-2).此外,FeN_(4)位点的单原子催化剂表现出较好的循环稳定性,在-0.8 V vs.RHE的电位下,经过20次循环测试,氨的法拉第效率仍能维持在80%左右.密度泛函理论计算结果表明,FeN_(4)位点对NO_(2)中间体和氢原子具有适宜的吸附能,有利于硝酸盐加氢进一步生成氨.相比之下,NO_(2)在ZnN_(4)位点上吸附很弱,导致NO_(2)容易从催化剂表面脱附至溶液中,形成亚硝酸盐副产物.此外,计算结果还显示,FeN_(4)位点上硝酸还原反应的决速步骤NO*→HNO*的自由能差仅为0.07 eV,进一步证实了FeN_(4)位点在硝酸盐还原合成氨反应中的优异活性.综上,本文系统研究了六种具有明确MN_(4)结构的金属酞菁催化剂在硝酸盐还原合成氨反应中的活性趋势,并探究了不同MN_(4)位点对硝酸盐还原的活性影响.结合密度泛函理论计算,揭示了不同MN_(4)位点对硝酸盐还原反应的机理.为深刻理解硝酸盐还原反应机制,指导设计高效活性位提供了参考. 展开更多
关键词 电催化 金属酞菁 金属-N_(4) 硝酸根还原成氨 活性趋势
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Projections of surface air temperature and precipitation in the 21st century in the Qilian Mountains,Northwest China,using REMO in the CORDEX 被引量:1
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作者 Lan-Ya LIU xue-jia wang +2 位作者 Xiao-Hua GOU Mei-Xue YANG Zi-Han ZHANG 《Advances in Climate Change Research》 SCIE CSCD 2022年第3期344-358,共15页
Qilian Mountains(QM)is an important ecological security barrier in China and has been significantly affected by climate change,it is therefore of great importance and necessity to project its future climate change usi... Qilian Mountains(QM)is an important ecological security barrier in China and has been significantly affected by climate change,it is therefore of great importance and necessity to project its future climate change using high-resolution climate models because of mountainous areas in the QM and relatively few targeted simulation analyses.In this study,we used the simulations of the regional climate model REMO with 25 km spatial resolution,driven by three different global climate models(MPI-ESM-MR,NorESM1-M,and HadGEM2-ES),to evaluate how annual and seasonal mean surface air temperature and precipitation in the QM are likely to change for three future periods(2011-2040,2041-2070,and 2071-2100)under two representative concentration pathways(RCP2.6 and RCP8.5).The REMO model,shows noticeable cold and wet biases compared to observations for the reference period(1971-2000)and air temperature simulation outperforms precipitation simulation.The REMO simulations exhibit a warm and wet centre around lake,indicating that the simulation are likely influenced by lake.Projections under RCP2.6 show regional warming reaching 1.74℃ during 2011-2100,characterized by an initial increase and a decrease afterwards.Under RCP8.5,air temperatures increase monotonously from 2011 to 2100,with a warming magnitude of 5.36℃ for 2071-2100 relative to 1971-2000.The overall change in regional-average annual precipitation is not evident during 2011-2100,with some increases or decreases in certain time periods.In the 2071-2100 both the strongest warming and precipitation increase are projected to occur in winter under both scenarios,while precipitation in summer and autumn is projected to decrease in the east of the QM for the three future periods.The results suggest that the QM is likely to experience drought conditions in warm seasons in the future,which could impact agricultural and livestock production. 展开更多
关键词 Qilian Mountains Climate projection REMO RCP scenario Regional climate model
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