Recent Advances in Transition Metal-Based Catalysts for Electrocatalytic Nitrate Reduction Reaction

The accumulation of excessive nitrate in the atmosphere not only jeopardizes human health but also disrupts the balance of the nitrogen cycle in the ecosystem.Among various nitrate removal technologies,electrocatalytic nitrate reduction reaction(eNO_(3)RR)has been widely studied for its advantages of being eco-friendly,easy to operate,and controllable under environmental conditions with renewable energy as the driving force.Transition metal-based catalysts(TMCs)have been widely used in electrocatalysis due to their abundant reserves,low costs,easy-to-regulate electronic structure and considerable electrochemical activity.In addition,TMCs have been extensively studied in terms of the kinetics of the nitrate reduction reaction,the moderate adsorption energy of nitrogen-containing species and the active hydrogen supply capacity.Based on this,this review firstly discusses the mechanism as well as analyzes the two main reduction products(N_(2)and NH_(3))of eNO_(3)RR,and reveals the basic guidelines for the design of efficient nitrate catalysts from the perspective of the reaction mechanism.Secondly,this review mainly focuses on the recent advances in the direction of eNO_(3RR)with four types of TMCs,Fe,Co,Ni and Cu,and unveils the interfacial modulation strategies of Fe,Co,Ni and Cu catalysts for the activity,reaction pathway and stability.Finally,reasonable suggestions and opportunities are proposed for the challenges and future development of eNO_(3)RR.This review provides far-reaching implications for exploring cost-effective TMCs to replace high-cost noble metal catalysts(NMCs)for eNO_(3)RR.

Identification of Dynamic Active Sites Among Cu Species Derived from MOFs@CuPc for Electrocatalytic Nitrate Reduction Reaction to Ammonia

Direct electrochemical nitrate reduction reaction(NITRR)is a promising strategy to alleviate the unbalanced nitrogen cycle while achieving the electrosynthesis of ammonia.However,the restructuration of the high-activity Cu-based electrocatalysts in the NITRR process has hindered the identification of dynamical active sites and in-depth investigation of the catalytic mechanism.Herein,Cu species(single-atom,clusters,and nanoparticles)with tunable loading supported on N-doped TiO_(2)/C are successfully manufactured with MOFs@CuPc precursors via the pre-anchor and post-pyrolysis strategy.Restructuration behavior among Cu species is co-dependent on the Cu loading and reaction potential,as evidenced by the advanced operando X-ray absorption spectroscopy,and there exists an incompletely reversible transformation of the restructured structure to the initial state.Notably,restructured CuN_(4)&Cu_(4) deliver the high NH_(3) yield of 88.2 mmol h^(−1)g_(cata)^(−1) and FE(~94.3%)at−0.75 V,resulting from the optimal adsorption of NO_(3)^(−) as well as the rapid conversion of^(*)NH_(2)OH to^(*)NH_(2) intermediates originated from the modulation of charge distribution and d-band center for Cu site.This work not only uncovers CuN_(4)&Cu_(4) have the promising NITRR but also identifies the dynamic Cu species active sites that play a critical role in the efficient electrocatalytic reduction in nitrate to ammonia.

Oxygen‑Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.

Selective synthesis of nitrate from air using a plasma-driven gas-liquid relay reaction system

The direct oxidation of nitrogen is a potential pathway to achieving the zero-carbon-emission synthesis of nitric acid or nitrate, because it does not involve ammonia synthesis and additional ammonia oxidation processes. However, the slow kinetics of nitrogen oxidation and the difficult selective control of oxidation products hinder the development of this process. In this study, a plasma-driven gas-liquid relay reaction system was developed to overcome these limitations. A typical feature of this reaction system is that it can efficiently generate NO_x under plasma exposure;moreover, the specific anions in the absorption solution can be oxidized to strong oxidants capable of relay oxidation of low-valence nitrogen oxides. This feature allows for the deep oxidation of nitrogen, thus enabling the oxidation products of nitrogen to exist in high-valence states in the absorption solution. For experimental verification, we achieved the 100% selective synthesis of nitrate under plasma exposure, with air as the supply gas and a sodium sulfate solution as the absorption solution.

Preparation of high purity ruthenium nitrosyl nitrate from spent Ru-Zn/ZrO_(2)catalyst

Preparation of high purity ruthenium nitrosyl nitrate using spent Ru-Zn/ZrO_(2)catalyst was studied,including melting and leaching to obtain potassium ruthenate solution,reduction,dissolving,concentrating and drying to obtain ruthenium trichloride,nitrosation and hydrolysis to obtain ruthenium nitrosyl hydroxide,removing of K^(+)and Cl^(-),and neutralization with nitric acid.The effects of temperature,concentration,time and pH on the yield and purity of intermediates and final product were studied,and the optimum process conditions were obtained.The yield of ruthenium nitrosyl nitrate is 92%,the content of ruthenium in high purity product is 32.16%,and the content of Cl^(-)and K^(+)are much less than 0.005%.The reaction kinetics of ruthenium nitrosyl chloride to ruthenium nitrosyl hydroxide was studied.The reaction orders of Ru(NO)Cl_(3)at 40,55 and 70℃are 0.39,0.37 and 0.39,respectively,while those of KOH are 0.16,0.15 and 0.17,respectively.The activation energy is-2.33 k J/mol.

Electrocatalysts with atomic-level site for nitrate reduction to ammonia

Ammonia(NH_(3))is an important raw material for modern agriculture and industry,being widely demanded to sustain the sustainable development of modern society.Currently,the industrial production methods of NH_(3),such as the traditional Haber-Bosch process,have drawbacks including high energy consumption and significant carbon dioxide emissions.In recent years,the electrocatalytic nitrate reduction reaction(NO_(3)RR)powered by intermittent renewable energy sources has gradually become a multidisciplinary research hotspot,as it allows for the efficient synthesis of NH_(3)under mild conditions.In this review,we focus on the research of electrocatalysts with atomic-level site,which have attracted attention due to their extremely high atomic utilization efficiency and unique structural characteristics in the field of NO_(3)RR.Firstly,we introduce the mechanism of nitrate reduction for ammonia synthesis and discuss the in-situ characterization techniques related to the mechanism study.Secondly,we review the progress of the electrocatalysts with atomic-level site for nitrate reduction and explore the structure-activity relationship to guide the rational design of efficient catalysts.Lastly,the conclusions of this review and the challenges and prospective of this promising field are presented.

Mesoporous Carbon Nanofibers Loaded with Ordered PtFe Alloy Nanoparticles for Electrocatalytic Nitrate Reduction to Ammonia

Highly dispersed bimetallic alloy nanoparticle electrocatalysts have been demonstrated to exhibit exceptional performance in driving the nitrate reduction reaction(NO_(3)RR)to generate ammonia(NH_(3)).In this study,we prepared mesoporous carbon nanofibers(mCNFs)functionalized with ordered PtFe alloys(O-PtFe-mCNFs)by a composite micelle interface-induced co-assembly method using poly(ethylene oxide)-block-polystyrene(PEO-b-PS)as a template.When employed as electrocatalysts,O-PtFe-mCNFs exhibited superior electrocatalytic performance for the NO_(3RR)compared to the mCNFs functionalized with disordered PtFe alloys(D-PtFe-mCNFs).Notably,the NH_(3)production performance was particularly outstanding,with a maximum NH_(3)yield of up to 959.6μmol/(h·cm~2).Furthermore,the Faraday efficiency(FE)was even 88.0%at-0.4 V vs.reversible hydrogen electrode(RHE).This finding provides compelling evidence of the potential of ordered PtFe alloy catalysts for the electrocatalytic NO_(3)RR.

Pollution characteristics of peroxyacetyl nitrate in karst areas in Southwest China

桂林是世界著名的地处喀斯特地区的旅游胜地,其光化学污染问题日益严重,过氧乙酰硝酸酯(PAN)被认为是光化学污染的可靠指标,也是本研究的重点.本研究于2021年10月首次观测了桂林的PAN的浓度为0.087-2.559ppb,同时探讨了PAN典型高值过程的成因.此次污染主要来源于东北方向污染气团的水平和高空输送,同时,高温,强辐射和低湿度等气象条件也促进了本地PAN的形成.本研究同时估算了桂林市的O3背景浓度为20.347ppb.这项研究为城市的光化学污染控制工作提供了理论基础。

Elucidating the Role of Mass Transfer in Electrochemical Redox Reactions on Electrospun Fibers

Mass transfer can tune the surface concentration of reactants and products and subsequently infl uence the catalytic perfor-mance.The morphology of nanomaterials plays an important role in the mass transfer of reaction microdomains,but related studies are lacking.Herein,a facile electrospinning technique utilizing cellulose was employed to fabricate a series of carbon nanofi bers with diff erent diameters,which exhibited excellent electrochemical nitrate reduction reaction and oxygen evolu-tion reaction activities.Furthermore,the microstructure of electrocatalysts could infl uence the gas-liquid-solid interfacial mass transfer,resulting in diff erent electrochemical performances.

Robust and highly efficient electrocatalyst based on ZIF-67 and Ni^(2+) dimers for oxygen evolution reaction:In situ mechanistic insight

Electrochemical water splitting is a straightforward process that involves two distinct reactions:the oxygen evolution reaction(OER)which produces oxygen(O_(2))and the hydrogen evolution reaction(HER)which generates hydrogen(H_(2)).However,in the whole process,the OER is a bottleneck as it requires more energy than a four-electron reaction involving critical raw materials(such as RuO_(2)or IrO_(2))as electrocatalysts.Therefore,here,we address the challenge of erratic kinetics/limited durability of OER in water electrolysis,In this paper,we demonstrate that the deposition of ultrasmall amounts of nickel(Ⅱ)nitrate in zeolitic imidazolate framework-67(ZIF-67)can be used as a general approach to enhance the electrocatalytic performance of the framework.We investigated the influence of Ni(NO_(3))·x6H_(2)O loading on ZIF-67(from 0.1 to 0.0001 M)and found that ZIF-67 enriched with only 0.001 M of Ni(NO_(3))2·x6H_(2)O(ZIF-670.001 Ni)exhibited massive promotion in OER.The ZIF-670.001 Ni showed a large specific surface area of 2577 m^(2)g^(-1),a low overpotential of 299 mV,a lower Tafel slope of 94.1 mA dec^(-1),and an outstanding overpotential retention of 99.8%(at 50 mA cm^(-2)).By conducting electron paramagnetic resonance(EPR)measurements,we also discovered that the 0.001 M of Ni(NO_(3))_(2)·x6H_(2)O loading in ZIF-67 introduces Ni^(^(2+))dimers,which contribute to the enhanced electroactivity of the modified ZIF-67.This phenomenon was further revealed during density-functional theory(DFT)calculations,which allowed us to identify different possible forms of Ni^(^(2+))dimers and modeling of active centers.Along with in situ experiments,we provide mechanistic insight into the OER mechanism under alkaline conditions and found that it follows the lattice oxygen mechanism(LOM).Our study proposes a facile and efficient room-temperature route to boost the electrochemical performance of ZIF-67 in OER.For the first time,we demonstrate that modifying ZIF-67 with an ultrasmall amount of different nickel(Ⅱ)salts opens a general route to enhance its electroactivity during water-splitting reactions.

Ultrasonically Assisted Regioselective Nitration of Aromatic Compounds in Presence of Certain Group V and VI Metal Salts

Ultrasonically assisted nitration reactions (USANR) with anilides, moderately activated and non-activated aromatic compounds underwent smoothly and afforded good yields of products with high regio selectivity. Observed longer reaction times (6 - 8 hrs.) in metal catalyzed reactions reduced to (1 - 2 hrs.) under sonication. When ortho position is blocked para derivatives are obtained, and ortho nitro products are obtained when para position is blocked. In case of USANR of aromatic carbonyl and related compounds the effect of sonication is much more effective. The reactions could be completed only in few minutes.

High-throughput mechanistic study of highly selective hydrogen-bonded organic frameworks for electrochemical nitrate reduction to ammonia

Hydrogen-bonded organic frameworks(HOFs),an emerging porous macrocyclic materials linked by hydrogen-bond,hold potential for gas separation and storage,sensors,optical,and electrocatalysts.Here,HOF-based electrocatalysts are rationally developed for nitrates reduction to ammonia,allowing not only to regulate wastewater pollution but also to accomplish carbon-neutral ammonia(NH_(3))synthesis.We preform high-throughput computational screening of thirty-six HOFs with various metals as active sites,denoted as HOF-M1,for nitrate reduction reaction(NO_(3)RR)toward NH_(3).We have implemented a hierarchical four-step screening strategy,and ultimately,HOF-Ti1 was selected based on its exceptional catalytic activity and selectivity in the NO_(3)RR process.Through additional analysis,we discovered that the d band center of the active metal sites serves as an effective parameter for designing and predicting the performance of HOFs in NO_(3)RR.This research not only showcases the immense potential of electrocatalysis in transforming NO_(3)RR into NH_(3)but also provides researchers with a compelling incentive to undertake further experimental investigations.

Zeolite-mediated hybrid Cu^(+)/Cu~0 interface for electrochemical nitrate reduction to ammonia

The electrocatalytic conversion of reactive nitrogen species to ammonia is a promising strategy for efficient NH_(3) synthesis.In this study,we reveal that the hybrid Cu^(+)/Cu~0 interface is catalytically active for electrochemical ammonia synthesis from nitrate reduction.To maintain the hybrid Cu^(+)/Cu~0 state at negative reaction potentials,hydrophilic zeolite is used to modify Cu/Cu_(2)O electrocatalyst,which demonstrates an impressive NH_(3) production rate of 41.65 mg h^(-1) cm^(-2)with ~100% Faradaic efficiency of ammonia synthesis at-0.6 V vs.RHE.In-situ Raman spectroscopy unveil the high activity originates from the zeolite reconstruction at the electrode–electrolyte interface,which protects the valence state of Cu~0/Cu^(+) site under negative potential and promotes electrochemical activity towards NH_(3) synthesis.

Recent progress and challenges in structural construction strategy of metal-based catalysts for nitrate electroreduction to ammonia

Ammonia plays an essential role in human production and life as a raw material for chemical fertilizers.The nitrate electroreduction to ammonia reaction(NO_(3)RR)has garnered attention due to its advantages over the Haber-Bosch process and electrochemical nitrogen reduction reaction.Therefore,it represents a promising approach to safeguard the ecological environment by enabling the cycling of nitrogen species.This review begins by discussing the theoretical insights of the NO_(3)RR.It then summarizes recent advances in catalyst design and construction strategies,including alloying,structure engineering,surface engineering,and heterostructure engineering.Finally,the challenges and prospects in this field are presented.This review aims to guide for enhancing the efficiency of electrocatalysts in the NO_(3)RR,and offers insights for converting NO_(3)-to NH_(3).

2,4,5-三碘基咪唑在微通道式反应器中的硝化反应

采用微通道式反应技术,以2,4,5-三碘基咪唑(2,4,5-TII)为原料,分别在20%、50%、65%、98%不同质量分数的硝酸中进行硝化反应,合成2,4,5-三硝基咪唑的咪唑盐(2,4,5-TNI咪唑盐);采用傅里叶变换红外光谱(FT-IR)、核磁共振光谱(NMR)、元素分析(EA)和熔点测定法等表征了产物结构。结果表明,采用微通道式硝化反应技术时,由2,4,5-TII制备2,4,5-TNI咪唑盐最优工艺条件为:2,4,5-TII与98%硝酸摩尔比为1∶20、在微通道式反应器停留时间6min、反应液温度70~72℃,得率为21.8%。微通道式反应工艺与常规釜式反应工艺相比,具有反应时间短、硝化试剂用量降低、反应温度略有降低、得率略有提高的优点,但也无法完全避免氧化副反应的发生。

1-甲基-2,4,5-三硝基咪唑的微通道合成技术

采用微通道式反应技术,分别以1-甲基-2,4-二硝基咪唑(2,4-MDNI)与硝硫混酸硝化反应、2,4,5-三硝基咪唑钾盐(2,4,5-TNIK)与硫酸二甲酯(DMS)甲基化反应,合成了1-甲基-2,4,5-三硝基咪唑(MTNI);采用傅里叶变换红外光谱(FT-IR)、核磁共振光谱(NMR)、元素分析(EA)、熔点等表征了其结构。结果表明,采用微通道反应技术,基于2,4-MDNI硝化工艺的最优条件为:2,4-MDNI和发烟硝酸摩尔比为2∶3、发烟硝酸和20%发烟硫酸体积比为1∶2、在微通道反应器中停留时间为12min、反应器中反应液温度为75℃,得率和纯度分别为78.1%和99.2%。基于2,4,5-TNIK甲基化工艺的最优条件为:2,4,5-TNIK、DMS和K2CO3摩尔比为1∶2∶2、在微通道反应器中停留时间为20min、反应温度为70℃,得率和纯度分别为71.3%和99.4%。由此可得,微通道式反应工艺与常规釜式反应工艺相比,具有反应时间短、硝化试剂用量少、反应温度略有降低、得率略有提高的优点。

电催化硝酸根还原合成氨:关于铁/铜基催化剂的研究展望

氨(NH_(3))是现代工业的重要化工原料之一,因其具有较高的能量密度、便于运输和储存的特点而被认为是一种非常有前景的储氢材料和可再生能源载体.电催化硝酸根还原(NO_(3)RR)是一种理想的绿色合成氨策略,同时可应用于废水中硝酸根(NO_(3)−)污染的去除.然而,NO_(3)RR涉及多个电子和质子转移过程,且存在析氢反应(HER)等竞争反应,导致NO_(3)RR的法拉第效率(FE)和选择性较低.近年来,精准构筑NO_(3)RR电催化剂,实现高效合成氨逐步成为电催化领域的研究热点.其中,铁/铜基催化剂因其优异的催化性能和经济可行性而备受关注.因此,对近年来具有代表性的铁/铜基催化剂的研究进展进行总结是非常必要的.本文首先简述了电化学NO_(3)RR合成氨可能发生的反应路径,主要围绕铁/铜基电催化剂在NO_(3)RR中可能涉及的反应历程和相应的中间体.在此基础上,针对不同的反应机理系统归纳了三种催化剂设计策略,包括单原子催化剂策略、双金属催化剂策略以及仿生催化剂策略等.随后,重点评析和讨论了原位实时表征技术,如原位电化学质谱、原位X射线吸收光谱和原位红外/拉曼等,在电催化NO_(3)RR合成氨研究领域中的代表性应用案例,并阐明了原位表征技术的发展和联用对于揭示NO_(3)RR本征活性位和动态机理的关键作用.最后,系统总结了当前NO_(3)RR所面临的核心挑战并对其未来的研究机遇和发展方向进行了展望,包括高效催化剂的关键描述符和设计策略,探究固-液界面的前沿原位表征技术开发,以及将NO_(3)RR与绿色反应(如二氧化碳转化和生物质转化等)高效耦联制备高值化学品.综上所述,尽管电催化NO_(3)RR合成氨目前仍面临诸多挑战,随着实验方案、科学理论和原位表征技术的不断发展,未来将会出现更多高效且稳定的NO_(3)RR催化剂.本文旨在为高效电催化剂的理性开发,深入理解其动态反应机理与催化剂构效关系提供参考.

新型过氧乙酰硝酸酯合成装置的设计与测试

本研究针对过氧乙酰硝酸酯(PAN)标准气体制备装置存在的技术问题进行了针对性改进,设计了基于四面阵LED和螺旋形反应管的新型PAN制备装置。测试结果表明:该装置输出气体的线性相关系数R2达到0.9998,梯度稳定性均可以满足现场使用的要求,可以为过氧乙酰硝酸酯分析仪提供可靠的校准和标定服务,有望在我国光化学监测网络建设中得到应用。

醋泡中药方与曲安奈德益康唑乳膏治疗手足癣患者的效果对比

目的:研究对比醋泡中药方与曲安奈德益康唑乳膏治疗手足癣患者的效果。方法:选择2021年1月—2022年6月湖北三峡职业技术学院附属医院收治的200例手足癣患者,以电脑编号随机法分为中药方组及参考组,各100例。中药方组采用醋泡中药方治疗,参考组使用曲安奈德益康唑乳膏治疗。对比两组治疗结果、不良反应发生率、复发情况及皮肤美容度。结果:中药方组总有效率较参考组更高(99.00%vs.87.00%),差异有统计学意义(P<0.05)。两组皮肤烧灼、瘙痒及色素沉着等轻微不良反应发生率对比,差异无统计学意义(P>0.05)。中药方组12个月复发率低于参考组(2.00%vs.9.00%),差异有统计学意义(P<0.05)。治疗后,两组皮肤美容度评分均低于治疗前,且中药方组各项皮肤美容度维度评分均低于参考组,差异均有统计学意义(P<0.05)。结论:醋泡中药方在治疗手足癣中的效果良好、不良反应情况较少,且在使用的过程中患者皮肤恢复程度高。

Co_(3)O_(4)/石墨炔异质界面用于高效硝酸根制氨

硝酸根还原反应(NtRR)是一种合成氨(NH3)的有效方法。催化剂的合成包括2步简单的工艺:首先在炭布(CC)上合成Co_(3)O_(4)纳米线,然后以六乙炔基苯(HEB)为前驱体在Co_(3)O_(4)表面生长石墨炔(GDY)(110°C, 10 h),从而可控合成Co_(3)O_(4)/GDY纳米线异质结催化剂。高分辨率扫描电镜(SEM)、透射电镜(HRTEM)、X射线光电子能谱(XPS)和拉曼表征等证实了Co_(3)O_(4)/GDY异质界面的成功合成,界面处形成的独特的sp-C―Co键以及GDY与Co之间的不完全电荷转移为催化反应提供了持续的电子供应,保证了NtRR的高效进行。Co_(3)O_(4)/GDY在NtRR中展现了优异催化性能,其NH_(3)产率(YNH3)和法拉第效率(FE)分别达到了0.78 mmol h^(-1)cm^(-2)和92.45%。这项工作为在温和条件下,从废水中高性能生产氨的异质结构提供了一种通用方法。