Ultrafine ordered L1_(2)-Pt-Co-Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.

Semi-closed synthesis of nitrogen and oxygen Co-doped mesoporous carbon for selective aqueous oxidation

Heteroatom-doped meso/micro-porous carbon materials are conventionally produced by harsh carbonization under an inert atmosphere involving specific precursors,hard/soft templates,and heteroatom-containing agents.Herein,we report a facile synthesis of N and O co-doped meso/micro-porous carbon(NOMC)by template-free carbonization of a small-molecule precursor in a semi-closed system.The semi-closed carbonizaiton process yields hydrophilic NOMCs with large surface area in a high yield.The porous structure as well as the elemental composition of NOMCs can be modulated by changing the holding time at a particular temperature.NOMCs as metal-free heterogeneous catalysts can selectively oxidize benzyl alcohol and its derivatives into aldehydes/ketones with>85%conversion in aqueous solution,which is much higher than that of the control sample obtained in tube furnace(21%conversion),mainly due to their high N content,high percentage of pyridinic N,and large surface area.The presence of O-containing moieties also helps to improve the hydrophilicity and dispersion ability of catalysts and thus facilitates the mass transfer process during aqueous oxidation.The NOMC catalysts also dispayed excellent activity for a wide range of substrates with a selectivity of>99%.

预置标记线在泪道内窥镜手术中的临床应用价值

目的:探讨应用预置标记线在泪道内窥镜手术中的临床应用价值,评估其对手术并发症的影响。方法:前瞻性临床研究。选取2015年6月至2018年12月在常熟市第二人民医院眼科就诊的泪道阻塞患者60例(60眼)进行泪道内窥镜手术,按患者住院号的单双号分为2组,单号作为对照组术中不预置标记线,即传统方法治疗;双号作为观察组,即先预置标记线。观察并记录2组患者术中泪道黏膜损伤、出血、穿孔(假道)、眼睑水肿及术后出血等并发症的发生情况。采用χ2检验对数据进行分析。结果:观察组术中可清晰地观察预置标记线的数量,结合泪道解剖学特征来判断泪道内窥镜探头所处位置,如泪道内窥镜下显示1根标记线提示在泪小管内;显示2根标记线汇聚处提示在泪总管内;显示2根标记线并且操作空间增大提示在泪囊内;显示2根标记线,可见黏膜皱襞提示在鼻泪管内。观察组术中泪道黏膜损伤发生率(16%)、术中出血发生率(13%)和眼睑水肿发生率(10%)明显低于对照组(分别为52%、52%、35%),差异均有统计学意义(χ2=8.543,P=0.003;χ2=8.718,P=0.003;χ2=4.069,P=0.044);而术中穿孔(假道)对照组中发生了1例,组间差异无统计学意义(χ2=0.001,P=0.973)。术后组间出血发生率差异无统计学意义(χ2=1.898,P=0.168)。2组中所有患者术中、术后出血量均为少量,术中注水后不影响操作,术后少许出血者2 d内均能自行止血。结论:泪道内窥镜手术中应用预置标记线能更好地操控内窥镜检查及手术,能准确定位操作所处的位置,可减少并发症的发生。