Synergy of sodium doping and nitrogen defects in carbon nitride for promoted photocatalytic synthesis of hydrogen peroxide

Photocatalytic synthesis of hydrogen peroxide has gradually become a promising method for in-situ pro-duction of hydrogen peroxide,which relies on sustainable solar energy.However,the commonly used photocatalyst,i.e.,carbon nitride(CN),still suffers from the drawbacks of narrow light absorption range and fast charge recombination.Here,we report a facile method to introduce nitrogen defects into carbon nitride together with sodium ion.By adjusting the ratio of sodium dicyandiamide,the band gap of carbon nitride can be controlled,while the carrier separation and transfer ability of carbon nitride is improved.The modified CN with sodium doping and nitrogen defect(SD-CN)demonstrates outstanding H_(2)O_(2)pro-duction performance(H_(2)O_(2)yield rate of 297.2μmol L^(−1)h^(−1))under visible light irradiation,which is approximately 9.8 times higher than that of pristine CN.This work deepens the understanding of the coordinated effect of structural defect and element doping of carbon nitride on the photocatalytic H_(2)O_(2)production performance,and provides new insight into the design of photocatalytic system for efficient production of H_(2)O_(2).

Tuning nitrogen defects and doping sulfur in carbon nitride for enhanced visible light photocatalytic activity

Defect construction and heteroatom doping are effective strategies for improving photocatalytic activity of carbon nitride(g-C_(3)N_(4)).In this work,N defects were successfully prepared via cold plasma.High-energy electrons generated by plasma can produce N defects and embed sulfur atoms into g-C_(3)N_(4).The N defects obviously promoted photocatalytic degradation performance that was 7.5 times higher than that of pure g-C_(3)N_(4).The concentration of N defects can be tuned by different power and time of plasma.With the increase in N defects,the photocatalytic activity showed a volcanic trend.The g-C_(3)N_(4)with moderate concentration of N defects exhibited the highest photocatalytic activity.S-doped g-C_(3)N_(4)exhibited 11.25 times higher photocatalytic activity than pure g-C_(3)N_(4).It provided extra active sites for photocatalytic reaction and improved stability of N defects.The N vacancy-enriched and S-doped g-C_(3)N_(4)are beneficial for widening absorption edge and improving the separation efficiency of electron and holes.

Tailoring sulfur-doped and nitrogen-defective carbon nitride nanosheets for efficient photo-controlled radical polymerizations

Despite the challenges that remain,the synergistic adjustment of various microstructures and photochemical parameters of graphitic carbon nitride(g-C_(3)N_(4))in photocatalytic reactions holds promises for improving catalytic efficiency and reducing energy consumption.Herein,sulfur-doped and nitrogen-defective g-C_(3)N_(4)(n-SC_(3)N_(x))nanosheets were designed and elaborately synthesized.The resultant n-SC_(3)N_(x)possessed a precisely defined 2D layer structure with extensive porosity and incremental specific surface area.Enhanced photoinduced electron transfer-reversible addition-fragmentation chain transfer(PET-RAFT)polymerization of vinyl monomers with low dispersity,excellent temporal control and high chain-end fidelity was achieved under mild blue light irradiation in a nondegassed system.Owing to their ultrathin nanostructures with nitrogen defects and sulfur dopants,n-SC_(3)N_(x)was capable of catalyzing RAFT polymerization in aqueous solutions at significantly accelerated rates,which were nearly 8 times faster compared to bulk g-C_(3)N_(4).The ease of separation and efficient reusability in subsequent polymerizations was enabled by the heterogeneous nature of n-SC_(3)N_(x).The appeal of this approach was illustrated by the fact that utilizing a reusable and metal-free photocatalyst in aqueous environments allowed for the synthesis of polymers with molecular weight up to 300 kg mol^(-1) and a dispersity of 1.32.

磷掺杂氮缺陷g-C_(3)N_(4)的合成及其光催化性能研究

以二氰胺和硫脲为混合前驱体,(NH4)2HPO4为磷源,采用热聚合联合快速高温法合成了磷掺杂氮缺陷石墨相氮化碳(g-C_(3)N_(4)),考察了前驱体配比、磷掺杂量和高温处理温度对g-C_(3)N_(4)结构和光催化活性的影响。结果表明,硫脲与二氰胺质量比为6∶4,磷掺杂量为5%,高温处理温度为700℃时,得到样品(DS60-5%-700)光催化性能最优。其在60min时对亚甲基蓝的降解效率为96.15%,分别较DS60-5%和DS60%提升了1.24倍和1.5倍。P掺杂和快速高温处理降低了g-C_(3)N_(4)的带隙值,扩宽了可见光的吸收范围,同时在g-C_(3)N_(4)结构中进入了氮缺陷,促使光生载流子的有效分离。

Defect-rich potassium amide: A new solid-state potassium ion electrolyte

One of the major obstacles to the application of potassium-ion batteries in large-scale energy storage is the lack of safe and effective electrolytes.KNH_(2),a new potassium-ion solid electrolyte has been developed in this study.Its ionic conductivity reaches 4.84×10^(-5)S cm^(-1)at 150°C and can reach3.56×10^(-4)S cm^(-1)after mechanochemical treatment.The result from electron paramagnetic resonance(EPR) measurement shows that the increment of ionic conductivity is dependent on the concentration of nitrogen defects in the KNH_(2) electrolyte.To the best of our knowledge,this is the first report that adopts inorganic amide as an electrolyte for potassium-ion battery and initiates the search for a new amidebased solid electrolyte for an all-solid-state potassium-ion battery.

钨基复合材料光催化固氮的研究进展

总结了光催化固氮反应的基本原理与反应途径,归纳了改善钨基光催化剂性能的方法,并对钨基复合材料光催化固氮的未来前景做出展望。

氮缺陷g-C_(3)N_(4)光降解罗丹明B

本文通过简单的一步煅烧法制备了氮缺陷g-C_(3)N_(4)光催化剂材料,并通过X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)以及紫外可见漫反射吸收光谱(UV-vis)对所制备的光催化剂的结晶度、形貌、特征官能团和光学特性方面进行了表征分析。与此同时,通过光降解罗丹明B的实验探究了所制备的光催化剂的光催化性能。实验结果表明,当罗丹明B的质量浓度为10 mg/L,催化剂的用量为20 mg时,氮缺陷g-C_(3)N_(4)具有优异的光降解性能,在20 min内对罗丹明B的光降解效率达到了100%。这表明缺陷的引入可以有效提高原始g-C_(3)N_(4)的光吸收范围,促进光生电子与空穴对的分离,增强其光催化效率。本研究为有机污染物的处理提供了一定的理论指导价值,具有一定的实际应用前景。

稀土离子掺杂调控MIL-101的电子结构促进电催化氮还原反应

电催化氮还原反应(electrocatalytic nitrogen reduction reaction,eNRR)被认为是在环境条件下生产低浓度NH_(3)/NH_(4)^(+)的有效策略,而设计合适的催化剂是高效驱动eNRR的关键。本研究采用水热法制备MIL-101催化剂,研究水热温度和Gd元素掺杂对MIL-101催化剂e NRR性能的影响。结果表明:150-MIL-101具有最高的结晶度及e NRR性能(氨产率为11.5μg/(h·mg),法拉第效率为30.5%)。MIL-101-0.5Gd表面下凹,暴露了内部粗糙孔结构,催化剂表观活性提高,同时氧空位浓度的增加可优化催化剂的特性活性,其在0.1mol/L LiClO_(4)电解质、-1.3 V电位下的氨产率和法拉第效率分别为16.7μg/(h·mg)和37.6%,优于无掺杂150-MIL-101,且催化剂具有较好的长期稳定性。

ML20MnTiB线材表面翘皮缺陷成因分析

借助光学显微镜及扫描电镜SEM对缺陷横截面的形貌、组分等进行检测,通过氮氧分析仪对成品线材的气体含量进行检验,认为因钢中氮含量高生成的大量TiN夹杂物是导致线材表面缺陷形成的根本原因。通过对ML20MnTiB生产过程加强控制,控制钢中氮含量≤0.0060%,可有效控制TiN夹杂物的生成,进而避免线材表面翘皮缺陷的产生。

铁型覆砂灰铸铁件氮气孔缺陷分析与改善措施

针对铁型覆砂铸造工艺生产灰铸铁件时产生的氮气孔缺陷,通过使用EDS能谱仪对氮气孔缺陷进行定性和定量分析,并结合铸件生产工艺对氮气孔的形成原因进行分析,通过在原材料上更换覆膜砂、提高新砂加入量、分开管理壳型线和铁型线回用砂,生产工艺上采取增加排气塞和提高铁型温度、固化时间、浇注温度等措施降低缺陷风险。改进后的工艺连续生产超过10万件产品,未再出现氮气孔缺陷。

N-Graphene Nanowalls via Plasma Nitrogen Incorporation and Substitution: The Experimental Evidence

Incorporating nitrogen(N)atom in graphene is considered a key technique for tuning its electrical properties.However,this is still a great challenge,and it is unclear how to build N-graphene with desired nitrogen configurations.There is a lack of experimental evidence to explain the influence and mechanism of structural defects for nitrogen incorporation into graphene compared to the derived DFT theories.Herein,this gap is bridged through a systematic study of different nitrogen-containing gaseous plasma post-treatments on graphene nanowalls(CNWs)to produce N-CNWs with incorporated and substituted nitrogen.The structural and morphological analyses describe a remarkable difference in the plasma–surface interaction,nitrogen concentration and nitrogen incorporation mechanism in CNWs by using different nitrogen-containing plasma.Electrical conductivity measurements revealed that the conductivity of the N-graphene is strongly influenced by the position and concentration of C–N bonding configurations.These findings open up a new pathway for the synthesis of N-graphene using plasma post-treatment to control the concentration and configuration of incorporated nitrogen for application-specific properties.

Polysulfide regulation by defect-modulated Ta_(3)N_(5-x) electrocatalyst toward superior room-temperature sodium-sulfur batteries

Resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging in metalsulfur batteries.Motivated by a theoretical prediction,herein,we strategically propose nitrogenvacancy tantalum nitride(Ta3N5-x)impregnated inside the interconnected nanopores of nitrogendecorated carbon matrix as a new electrocatalyst for regulating sulfur redox reactions in roomtemperature sodium-sulfur batteries.Through a pore-constriction mechanism,the nitrogen vacancies are controllably constructed during the nucleation of Ta3N5-x.The defect manipulation on the local environment enables well-regulated Ta 5d-orbital energy level,not only modulating band structure toward enhanced intrinsic conductivity of Ta-based materials,but also promoting polysulfide stabilization and achieving bifunctional catalytic capability toward completely reversible polysulfide conversion.Moreover,the interconnected continuous Ta3N5-x-in-pore structure facilitates electron and sodium-ion transport and accommodates volume expansion of sulfur species while suppressing their shuttle behavior.Due to these attributes,the as-developed Ta3N5-x-based electrode achieves superior rate capability of 730 mAh g-1 at 3.35 A g-1,long-term cycling stability over 2000 cycles,and high areal capacity over 6 mAh cm-2 under high sulfur loading of 6.2 mg cm-2.This work not only presents a new sulfur electrocatalyst candidate for metal-sulfur batteries,but also sheds light on the controllable material design of defect structure in hopes of inspiring new ideas and directions for future research.

Applying heteroatom co-doped carbon nanotube for manifesting high performance in the electrochemical reduction of aqueous nitrogen oxide by gold nanoparticles

Electrochemical NO-to-NH_(3) under ambient conditions could be a viable alternative having advantages in terms of energy consumption and exhaust gas recycling of NO,replacing a traditional ammonia synthesis method of the Haber–Bosch process.In synthesizing boron(B-)and nitrogen(N-)co-doped carbon nanotube(CNT)based gold(Au)catalysts,B-dopants elevate the conductivity of carbon nanotube by sp2 hybridization on graphene and implant B–N domains within the graphene layer,and result in facilitating the embedding amount of Au accompanied by high dispersibility with low particle size.Theoretical density functional theory(DFT)calculations elucidate that the electron cloud transmitted from B-dopant to the active site of Au induces the Lewis acidic site,and the O-distal pathway occurs following a spontaneous reaction.Increment of the electron-deficient B-doping area accompanied by N-defects and B–O edges retains the major valence state of Au as Au^(δ+),and suppresses hydrogen evolution reaction(HER)by repulsing the hindrance of H*.This record exhibits the highest faradaic efficiency(FE)of 94.7%,and NH_(3) yield rate of 1877.4μg·h^(-1)·mg_(cat)^(-1),which is the optimal yield over energy consumption in the field of the ambient reduction of aqueous NO.

Defect and nanostructure engineering of polymeric carbon nitride for visible-light-driven CO_(2) reduction

Sunlight-induced photocatalytic carbon dioxide(CO_(2))reduction to energy-rich chemicals by metal-free polymeric carbon nitride(CN)semiconductor is a promising tactic for sustained solar fuel production.However,the reaction efficiency of CO_(2)photoreduction is restrained seriously by the rapid recombination of photogenerated carriers on CN polymer.Herein,we incorporate 2-aminopyridine molecule with strong electron-withdrawing group into the skeleton edge of CN layers through a facile one-pot thermal polymerization strategy using urea as the precursor,which renders a modified carbon nitride(ACN)with extended optical harvesting,abundant nitrogen defects and ultrathin nanosheet structure.Consequently,the ACN photocatalyst with desirable structural features attains enhanced separation and migration of photoexcited charge carriers.Under visible light irradiation with Co(bpy)^(2+)_(3)as a cocatalyst,the optimized ACN sample manifests a high CO_(2)deoxygnative reduction activity and high sta-bility,providing a CO yielding rate of 17μmol h^(-1),which is significantly higher than that of pristine CN.The key intermediates engaged in CO_(2)photoreduction reaction are determined by the in situ diffuse reflectance infrared Fourier transform spectroscopy,which sponsors the construction of the possible photocatalytic CO_(2)reduction mechanism on ACN nanosheets.

LaFeO_(3)/CQDs-g-C_(3)N_(x)催化剂的光催化性能研究

本实验制备了一种Z型含氮缺陷的石墨相氮化碳(LaFeO_(3)/CQDs-g-C_(3)N_(x))复合光催化剂。利用X射线衍射(XRD)、紫外-可见光漫反射(UV-Vis DRS)、光致发光光谱(PL)、扫描电镜(SEM)、透射电镜(TEM)以及X射线光电子能谱(XPS)等手段对催化剂进行了表征。结果表明,氮缺陷和CQDs的引入能增强光生载流子的迁移效率。LaFeO_(3)/CQDs-g-C_(3)N_(x)复合材料对罗丹明B(RhB)的光催化降解率是纯g-C_(3)N_(4)的3.98倍,并具有良好的光催化稳定性。同时对抗生素和其他有机污染物也表现出良好的降解能力。

Ultrafine MoO_(x)clusters anchored on g-C_(3)N_(4)with nitrogen/oxygen dual defects for synergistic efficient O_(2)activation and tetracycline photodegradation

Photocatalytic O_(2)activation to generate reactive oxygen species is crucially important for purifying organic pollutants,yet remains a challenge due to poor adsorption of O_(2)and low efficiency of electron transfer.Herein,we demonstrate that ultrafine MoO_(x)clusters anchored on graphitic carbon nitride(g-C_(3)N_(4))with dual nitrogen/oxygen defects promote the photocatalytic activation of O_(2)to generate·O_(2)−for the degradation of tetracycline hydrochloride(TCH).A range of characterization techniques and density functional theory(DFT)calculations reveal that the introduction of the nitrogen/oxygen dual defects and MoO_(x)clusters enhances the O_(2)adsorption energy from−2.77 to−2.94 eV.We find that MoO_(x)clusters with oxygen vacancies(Ov)and surface Ov-mediated Moδ+(3≥δ≥2)possess unpaired localized electrons,which act as electron capture centers to transfer electrons to the MoO_(x)clusters.These electrons can then transfer to the surface adsorbed O_(2),thus promoting the photocatalytic conversion of O_(2)to·O_(2)−and,simultaneously,realizing the efficient separation of photogenerated electron–hole pairs.Our fully-optimized MoO_(x)/g-C_(3)N_(4)catalyst with dual nitrogen/oxygen defects manifests outstanding photoactivities,achieving 79%degradation efficiency toward TCH within 120 min under visible light irradiation,representing nearly 7 times higher activity than pristine g-C_(3)N_(4).Finally,based on the results of liquid chromatograph mass spectrometry and DFT calculations,the possible photocatalytic degradation pathways of TCH were proposed.

氮掺杂工艺以及退火处理对直拉法单晶硅的影响

随着集成电路的飞速发展,要求超大规模集成电路用硅片具有更少的晶格缺陷及更低的有害杂质含量。因此,在晶体生长和器件制造过程中,必须对缺陷进行很好地控制,缺陷在硅材料的质量控制中起着关键作用。近年来通过氮掺杂控制缺陷动力学并改变缺陷的演变已被广泛应用于直拉法单晶硅中。本文以氮掺杂技术为基础,介绍了氮掺杂剂的基本性质及其与CZ硅中点缺陷的相互作用,氮掺杂对氧沉淀物、空洞的影响,以及退火处理对晶体原生颗粒、体微缺陷等的影响。

内置硬质α缺陷的TC4疲劳寿命试验研究

硬质α缺陷是TC4钛合金冶金过程中不可避免引入的一种缺陷,性质与钛合金基体差异较大,因而成为影响钛合金部件可靠使用的重要因素。为探究硬质α缺陷对于钛合金试件疲劳寿命的影响规律,克服冶金过程中产生硬质α缺陷尺寸不可检出的困难,制备了内置硬质α缺陷的TC4钛合金试验件,开展了低循环疲劳试验。采用面积等效法将夹杂尺寸等效为裂纹,并结合Franc3D程序,确定了内置不同含氮量的硬质α缺陷试验件裂纹萌生寿命。从试验结果中分析可得,硬质α缺陷会降低TC4钛合金的疲劳寿命,但存在一个含氮量的阈值。

金刚石NV色心在钢丝绳缺陷检测中的应用

氮-空位(NV)色心是金刚石中的一种晶格缺陷,由于其具有优异的自旋性质和光学性质,在量子精密测量领域受到广泛关注。利用金刚石的高灵敏度和高分辨率磁测量特性,实现灵敏且准确的钢丝绳缺陷检测。在磁场测量方面,该技术使用光学探测磁共振法测出NV色心的共振频率,从而计算出外界的磁场强度。在钢丝绳检测方面,以浓度为1.8×10^(17)~3.6×10^(17)的NV色心磁传感器为核心组成探头模块,三块高度集成的现场可编程门阵列(FPGA)板卡组成控制模块,搭建量子精密测量平台,检测钢丝绳断丝缺陷和微弱磨损缺陷。实验结果表明,该系统的磁场测量灵敏度可达6 nT/Hz,空间分辨率为200μm,可以对钢丝绳缺陷进行准确检测,为工业安全提供了新的检测方式。

氮对金刚石缺陷发光的影响

利用低温显微荧光光谱研究了IIa型、Ib型、Ia型金刚石的缺陷发光性质.研究发现,随着氮含量增加,间隙原子及空位逐渐被氮原子所束缚,从而使得GR1中心、533.5 nm及580 nm中心等本征缺陷发光减弱,而氮-空位复合缺陷(NV中心)及523.7 nm中心等氮相关缺陷发光增强.高温退火后,间隙原子与空位可以自由移动,IIa型金刚石中出现了NV^0中心,Ib型金刚石中只剩下了NV中心,Ia型金刚石中氮原子之间发生团聚,出现了H3中心及N3中心.另外,氮作为施主原子,有利于负电荷缺陷的形成,如3H中心、NV中心.