氮硫共掺杂高比表面中空碳球的制备及其在电催化二氧化碳还原中的应用

化石燃料是现代能源体系的重要支柱,其大量使用导致大气中CO2浓度不断增加,加剧了全球变暖和环境恶化.因此,各国研究人员开发了大量技术手段以捕获和重新再利用CO2这一丰富的碳资源.其中, CO2电催化还原(CO2RR)技术在减少CO2排放和将其转化为有用化学品等方面极具潜力.但是, CO2RR具有反应能垒高和动力学过程缓慢等特点,进而限制其转化效率,故使用传统的贵金属材料(Ag, Au, Cu及Pd等)作为CO2RR高效的催化剂.然而,贵金属材料的大规模应用受限于它们成本高昂、稳定性差及环境毒性等缺点.在各类可替代贵金属催化剂中,碳材料因其廉价丰富、结构可调和导电性高的特点在CO2RR应用上展现出诱人的前景,因此,探索合适的碳基催化剂在高效催化二氧化碳领域具有重要的研究价值和意义.本文通过简单有效的方法制备了一种氮硫共掺杂的高比表面的碳基催化剂(SZ-HCN)用于CO2RR.首先利用表面活性剂胶束Triton X-100作为模板诱导调控,合成了具有中空结构的苯胺-吡咯共聚物,并以此为碳前驱体,通过一步热解共聚物和硫粉获得N和S共掺杂多孔碳,材料的高比表面积(1510 m2g–1)得益于中空结构和ZnCl2盐造成的纳米孔结构.值得注意的是,高比表面的多孔结构且有效共掺杂N/S,能提供更多的高活性催化位点和有利于相关反应物种的传输.通过扫描电子显微镜、高分辨透射电子显微镜、高角环形暗场-扫描透射-元素分布、N2吸脱附等温分析及X射线光电子能谱等物理表征证实了催化剂材料的中孔结构和N/S共掺杂组分.进一步通过电化学测试分析和产物测试分析可知,电催化剂SZ-HCN在-0.60 V还原CO2为CO的法拉第效率高达93%,明显抑制竞争反应HER.此外,在-0.60 V恒电位下连续20 h测试,依旧保持稳定的电流密度(-5.2 m A cm–2)和高的CO选择性,显示了出色的耐久性和潜在应用性.我们采用密度泛函数理论探究N和S掺杂的影响,模拟计算可知,相比单一N掺杂的催化剂, N, S共掺杂可以提供更多的活性位点,降低CO2还原为CO反应中决速步生成COOH*的吉布斯自由能垒,进而提高催化活性.SZ-HCN催化剂展现出的优异CO2RR活性和稳定性主要归因于:(1)N和S元素均匀掺杂到碳基体中,两者的协同效应导致碳电荷再分布形成高活性位点,提高本征活性;(2)高比表面的多级孔结构提供了丰富的三相接触界面和有利的传输通道,便于反应相关物种的快速转移.该碳基催化剂材料在替代贵金属应用于CO2RR展示了一定的潜力.

Comparison of Ex‑PRESS implantation versus trabeculectomy combined with phacoemulsification in primary open‑angle glaucoma:a retrospective in vivo confocal microscopy study

Background:To compare the efficacy of Ex-PRESS implantation versus trabeculectomy combined with phacoemulsification.Methods:A retrospective 12-month study on patients with coincident primary open-angle glaucoma(POAG)and cataract.The patients underwent combined phacoemulsification and Ex-PRESS implant(Phaco-ExPRESS,n=35)or phacotrabeculectomy(Phaco-Trab,n=35).The morphological structures of the filtering bleb were examined by slitlamp,anterior segment optical coherence tomography(AS-OCT)and in vivo confocal microscopy(IVCM).Complete success was defined as postoperative intraocular pressure(IOP)<18 mmHg without the use of anti-glaucoma medication.Qualified success was defined as postoperative IOP<18 mmHg with or without anti-glaucoma medications.The data were collected preoperatively and postoperatively at 2 weeks,1 month,3 months,6 months,and 12 months.Results:No significant difference in the variables such as age,IOP and perimetry was found between the groups of Phaco-ExPRESS and Phaco-Trab.At the one-year postoperative visit for filtering blebs,Phaco-ExPRESS increased the mean area of epithelial microcysts significantly from 0.10±0.05 to 0.20±0.09μm^(2)perμm^(2),while Phaco-Trab decreased the mean area significantly from 0.08±0.04 to 0.04±0.06μm^(2)perμm^(2).Notably,the hyperreflective dots detected by IVCM decreased by 84.9%in Phaco-ExPRESS but increased by 36.3%in Phaco-Trab.The hyperreflective dots were further identified as neutrophil-and monocyte-like cells.The number of these cells were negatively correlated with the microcysts area(r=−0.7,P<0.01)but positively associated with the grade of connective tissue(r=0.5,P<0.01).By creating different microstructural changes in the filtering blebs,Phaco-ExPRESS produced a higher complete success rate(84.9%vs.41.2%,P<0.01)and significant decrease in the number of anti-glaucoma medications(P<0.01)when compared with those in Phaco-Trab.However,the qualified success showed no significant difference between the two groups(100.0%vs.91.2%,P=0.24).Conclusions:At the one-year follow-up,Phaco-ExPRESS generated better filtering bleb with larger area of microcysts,looser connective tissues,and less inflammation than that of Phaco-Trab,providing adequate IOP control and less IOP-lowering medications.These findings indicate that Phaco-ExPRESS could be more preferred than Phaco-Trab for the treatment of patients with coincident POAG and cataract.

Grain Boundaries Engineering of Hollow Copper Nanoparticles Enables Highly Efficient Ammonia Electrosynthesis from Nitrate

Electrochemical nitrate reduction reaction(NO_(3)−RR)is an ideal route to produce ammonia(NH_(3))under ambient conditions.Although a markedly improved NH3 production rate has been achieved on the NO_(3)−RR compared with the nitrogen reduction reaction(NRR),the NH_(3) production rate of NO_(3)−RR is still well below the industrial Haber-Bosch route due to the lack of robust electrocatalysts for yielding high current densitieswith concurrently good suppression of hydrogen evolution reaction(HER).Herein,we describe an in situ electrochemical strategy for the synthesis of hollow carbon-coated Cu nanoparticles(NPs)(HSCu@C)with abundant grain boundaries(HSCu-AGB@C)for highly efficient NO_(3)−RR in both alkaline and neutral media.Impressively,in alkaline media,the HSCu-AGB@C can achieve a maximum NH3 Faradaic efficiency of 94.2% with an ultrahigh NH_(3) rate of 487.8 mmol g^(−1) cat h^(−1) at−0.2 V versus a reversible hydrogen electrode,more than 2.4-fold of the rate obtained in the Haber-Bosch.Both theoretic computations and experimental results uncover that the grain boundaries play the key to improve the NO_(3)−RR performance.Herein,the industrial-scale NH_(3) production ratemay open exciting opportunities for the practical electrosynthesis NH_(3) under ambient conditions.