Controllably partial removal of thiolate ligands from unsupported Au_(25) nanoclusters by rapid thermal treatments for electrochemical CO_(2)reduction

Colloidal synthesis of metal nanoclusters will inevitably lead to the blockage of catalytically active sites by organic ligands.Here,taking[Au_(25)(PET)_(18)]-(PET=2-phenylethanethiol)nanocluster as a model catalyst,this work reports a feasible procedure to achieve the controllably partial removal of thiolate ligands from unsupported[Au_(25)(PET)_(18)]-nanoclusters with the preservation of the core structure.This procedure shortens the processing duration by rapid heating and cooling on the basis of traditional annealing treatment,avoiding the reconfiguration or agglomeration of Au_(25)nanoclusters,where the degree of dethiolation can be regulated by the control of duration.This work finds that a moderate degree of dethiolation can expose the Au active sites while maintaining the suppression of the competing hydrogen evolution reaction.Consequently,the activity and selectivity towards CO formation in electrochemical CO_(2)reduction reaction of Au_(25)nanoclusters can be promoted.This work provides a new approach for the removal of thiolate ligands from atomically precise gold nanoclusters.

Recent developments of nanocarbon based supports for PEMFCs electrocatalysts

Nanocarbons,widely and commonly used as supports for supported Pt-based electrocatalysts in PEMFCs,play a significant role in Pt dispersion and accessibility,further determining their corresponding electrocatalytic performance.This paper provides an overview of the nanoarchitectures and surface physicochemical properties of nanocarbons affecting the electrocatalyst performance,with an emphasis on both physical characteristics,including pore structure,and chemical properties,including heteroatom doping and functional carbon-based supports.This review discusses the recent progress in nanocarbon supports,guides the future development direction of PEMFC supports,and provides our own viewpoints for the future research and design of PEMFCs catalysts,advancing the commercialization of PEMFCs.

Enhanced electrocatalytic activity for H_2O_2 production by the oxygen reduction reaction: Rational control of the structure and composition of multi-walled carbon nanotubes

Hydrogen peroxide(H2O2)is a very useful chemical reagent,but the current industrial methods for its production suffer from serious energy consumption problems.Using high-activity and high-selectivity catalysts to electrocatalyze the oxygen reduction reaction(ORR)through a two-electron(2e^-)pathway is a very promising route to produce H2O2.In this work,we obtained partially oxidized multi-walled carbon nanotubes(MWCNTs)with controlled structure and composition by oxidation with concentrated sulfate and potassium permanganate at 40℃ for 1 h(O-CNTs-40-1).The outer layers of O-CNTs-40-1 are damaged with defects and oxygen-containing functional groups,while the inner layers are maintained intact.The optimized structure and composition of the partially oxidized MWCNTs ensure that O-CNTs-40-1 possesses both a sufficient number of catalytic sites and good conductivity.The results of rotating ring disk electrode measurements reveal that,among all oxidized MWCNTs,O-CNTs-40-1 shows the greatest improvement in hydrogen peroxide selectivity(from ~ 30% to ~ 50%)and electron transfer number(from ~ 3.4 to ~ 3.0)compared to those of the raw MWCNTs.The results of electrochemical impedance spectroscopy measurements indicate that both the charge-transfer and intrinsic resistances of O-CNTs-40-1 are lower than those of the raw MWCNTs and of the other oxidized MWCNTs.Finally,direct tests of the H2O2 production confirm the greatly improved catalytic activity of O-CNTs-40-1 relative to that of the raw MWCNTs.

An Fe-N/S-C hybrid electrocatalyst derived from bimetal-organic framework for efficiently electrocatalyzing oxygen reduction reaction in acidic media

Heteroatoms doped Fe-N-C electrocatalysts have been widely acknowledged as one of the most promising candidates to replace Pt-based materials for electrocatalyzing oxygen reduction reaction(ORR).However,the complicated synthesis method and controversial catalytic mechanism represent a substantial impediment as of today.Herein,a very facile strategy to prepare Fe-N/S-C hybrid through pyrolyzing Zn and Fe bimetallic MOFs is rationally designed.The electrocatalytic ORR performance shows a volcanotype curve with the increment of added Fe content.The half-wave potential(E1/2) for ORR at optimized Fe-N/S-C-10%(10%=n(Fe)/(n(Fe)+n(Zn)),n(Fe) and n(Zn) represent the moles of Fe2+ and Zn2+ in the precursors,respectively) shifts significantly to the positive direction of 19.6 mV with respect to that of Pt/C in acidic media,as well as a high 4 e selectivity and methanol tolerance.After 10,000 potential cycles,E1/2 exhibits a small negative shift of-27.5 mV at Fe-N/S-C-10% compared favorably with Pt/C(~141.0 mV).This can be attributed to:(ⅰ) large specific surface area(849 m^(2)/g) and hierarchically porous structure are favorable for the rapid mass transfer and active sites exposure;(ⅱ) the embedded Fecontaining nanoparticles in porous carbon are difficult to be moved and further agglomerated during the electrochemical accelerated aging test,further improving its stability;(ⅲ) there exist small Fecontaining nanoparticles,uniformly doped N and S,abundant Fe-N as efficiently active sites.This work represents a breakthrough in the development of high-efficient non-precious-metal catalysts(NPMCs)to address the current Pt-based electrocatalysts challenges.

Investigation on the coordination mechanism of Pt-containing species and qualification of the alkaline content during Pt/C preparation via a solvothermal polyol method

A solvothermal assisted ethylene glycol reduction method is a common technology for Pt/C catalysts preparation. Here, the coordination mechanism of the Pt-containing species is deeply studied by innovatively adopting the ultraviolet-visible spectroscopy technology and H+ concentration detector. Moreover, the amount of Na OH that effectively coordinates Pt4+ has been tentatively qualified and the heating parameters during the preparation process of Pt/C have also been optimized. As investigated, the optimized 20-(1/22)-140-2 Pt/C(20 wt%Pt;m(Pt):m(Na OH)=1/22;heating temperature: 140 °C, heating time: 2 h) exhibits higher electrocatalytic activity towards oxygen reduction reaction(ORR) than the commercial 20 wt% Pt/C(E-TEK) in acidic media. This work provides a theoretical reserve and technical accumulation for industrialized mass production of highly efficient Pt/C catalysts for ORR in proton exchange membrane fuel cells.

Template-free synthesis of Co_(3)O_(4)microtubes for enhanced oxygen evolution reaction

To fully exploit the superiority of tubular structures,in this study,we systematically explore the optimal preparation conditions for Ni/Co_(3)O_(4),including cation species and content,additive species and content,and anion species.Our results reveal that the formation of an initial cobalt nickel acetate hydroxide prism is the key factor and directly affects the final microtubular structure.Moreover,P is subsequently doped into the Ni/Co_(3)O_(4)lattice to increase the M^(3+)/M^(2+)molar ratio(M=Co and Ni),promote reaction kinetics,and optimize electronic structure.Consequently,the oxygen evolution reaction performance of P-doped tubular Ni/Co_(3)O_(4)is significantly higher than that of undoped Ni/Co_(3)O_(4)and the state-of-the-art RuO_(2)electrocatalyst.

Analysis on Volatile Components of Flowers and Leaves of Thymus mongolicus by SPME-GC/MS

[Objectives] To analyze volatile components of flowers and leaves of Thymus mongolicus. [Methods]Volatile components of collected T. mongolicus flower and leaves were separated by headspace solid-phase microextraction( SPME) and identified by gas chromatography/mass spectrometry( GC/MS) and normallized by peak area. [Results] A total of 24 and 14 compounds were identified from flowers and leaves of T. mongolicus in the total ion chromatogram,accounting for 99. 573% and 97. 187% of the total peak area,respectively. Main components of flowers and leaves of T. mongolicus include phenols and terpenes,and thymol accounts for 35. 38% and 49. 13% of flowers and leaves of T. mongolicus,respectively. [Conclusions] SPME-GC/MS can be applied in analyzing volatile components of flowers and leaves of T. mongolicus,to provide basis for further development and utilization of T. mongolicus.

Constructing oxygen vacancy‐regulated cobalt molybdate nanoflakes for efficient oxygen evolution reaction catalysis

Oxygen evolution reaction(OER)is the dominant step for plenty of energy conversion and storage technologies.However,the OER suffers from sluggish kinetics and high overpotential due to its complex 4‐electron/proton transfer mechanism.Thus,developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge.Herein,we have synthesized the novel cobalt molybdate nanoflakes(CoMoO_(4)‐O_(v)‐n@GF)with adjustable oxygen vacancies contents by in situ constructing CoMoO_(4) nanoflakes on graphite felt(GF)and annealing treatment under the reduction atmosphere.The best‐performing CoMoO_(4)‐O_(v)‐2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential(296 mV at 10 mA cm^(‒2))and also small Tafel slope(62.4 mV dec^(‒1))in alkaline solution,which are comparable to those of the RuO_(2)@GF.The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO_(4) can expose more active sites,narrow the band‐gap to increase the electrical conductivity,and modulate the free energy of the OER‐related intermediates to accelerate OER kinetics,thus improving its intrinsic activity.

环境信息披露对企业可持续发展能力的影响研究——来自于重污染行业的经验数据

本文选取2012—2021年A股上市公司重污染行业的企业作为研究对象,对环境信息披露质量对于企业可持续发展能力的作用关系进行实证分析。研究发现:环境信息披露对企业可持续发展能力具有显著的正向影响,高质量的环境信息披露会促进企业可持续发展。市场竞争程度可以降低环境信息披露对企业可持续发展能力的促进作用,企业所处的市场环境竞争程度越大,环境信息披露对企业可持续发展能力的影响越小。重污染企业环境信息披露对企业可持续发展能力的提升效应在非国有企业和高竞争度的市场环境中更为明显。本文的研究结论有助于深入理解环境信息披露和企业可持续发展能力之间的关系,为如何提升企业可持续发展能力提出了新的角度与思路。

Structure–performance relationship of Au nanoclusters in electrocatalysis:Metal core and ligand structure

Remarkable progress has characterized the field of electrocatalysis in recent decades,driven in part by an enhanced comprehension of catalyst structures and mechanisms at the nanoscale.Atomically precise metal nanoclusters,serving as exemplary models,significantly expand the range of accessible structures through diverse cores and ligands,creating an exceptional platform for the investigation of catalytic reactions.Notably,ligand‐protected Au nanoclusters(NCs)with precisely defined core numbers offer a distinct advantage in elucidating the correlation between their specific structures and the reaction mechanisms in electrocatalysis.The strategic modulation of the fine microstructures of Au NCs presents crucial opportunities for tailoring their electrocatalytic performance across various reactions.This review delves into the profound structural effects of Au NC cores and ligands in electrocatalysis,elucidating their underlying mechanisms.A detailed exploration of the fundamentals of Au NCs,considering core and ligand structures,follows.Subsequently,the interaction between the core and ligand structures of Au NCs and their impact on electrocatalytic performance in diverse reactions are examined.Concluding the discourse,challenges and personal prospects are presented to guide the rational design of efficient electrocatalysts and advance electrocatalytic reactions.

绿色信贷政策与企业环保投资

本文以2012年《绿色信贷指引》政策的颁布为准自然实验,以2008—2020年全国沪、深A股上市公司为样本,运用双重差分法考察绿色信贷政策对重污染行业企业环保投资的影响。研究表明:绿色信贷政策的实施通过绿色信贷约束机制倒逼重污染行业企业加大环保投资。媒体负面关注越多,绿色信贷政策对环保投资的提升效应越明显;商业信用降低绿色信贷政策对重污染行业企业环保投资的提升效应;重污染企业外部融资依赖度越高,绿色信贷政策对环保投资的提升效应越大。绿色信贷政策对重污染企业的环保投资的提升效应在国有企业、大规模企业更明显;在金融发展水平低的地区、东部地区绿色信贷政策对环保投资的影响小,而中西部地区受绿色信贷政策的影响较大。本文的研究结论为绿色信贷政策对环保投资的激励作用提供了经验证据。

Recent Advances in the Understanding of the Surface Reconstruction of Oxygen Evolution Electrocatalysts and Materials Development

The electrochemical oxygen evolution reaction(OER)plays an important role in many clean electrochemical energy storage and conversion systems,such as electrochemical water splitting,rechargeable metal–air batteries,and electrochemical CO_(2) reduction.However,the OER involves a complex four-electron process and suffers from intrinsically sluggish kinetics,which greatly impairs the efficiency of electrochemical systems.In addition,state-of-the-art RuO2-based OER electrocatalysts are too expensive and scarce for practical applications.The development of highly active,cost-effective,and durable electrocatalysts that can improve OER performance(activity and durability)is of significant importance in realizing the widespread application of these advanced technologies.To date,considerable progress has been made in the development of alternative,noble metal-free OER electrocatalysts.Among these alternative catalysts,transition metal compounds have received particular attention and have shown activities comparable to or even higher than those of their precious metal counterparts.In contrast to many other electrocatalysts,such as carbon-based materials,transition metal compounds often exhibit a surface reconstruction phenomenon that is accompanied by the transformation of valence states during electrochemical OER processes.This surface reconstruction results in changes to the true active sites and an improvement or reduction in OER catalytic performance.Therefore,understanding the self-reconstruction process and precisely identifying the true active sites on electrocatalyst surfaces will help us to finely tune the properties and activities of OER catalysts.This review provides a comprehensive summary of recent progress made in understanding the surface reconstruction phenomena of various transition metal-based OER electrocatalysts,focusing on uncovering the correlations among structure,surface reconstruction and intrinsic activity.Recent advances in OER electrocatalysts that exhibit a surface self-reconstruction capability are also discussed.We identify possible challenges and perspectives for the development of OER electrocatalysts based on surface reconstruction.We hope this review will provide readers with some guidance on the rational design of catalysts for various electrochemical reactions.

政治关联、债务重组与盈余管理程度

本文以2007—2013年沪、深两市发生债务重组和配对的未债务重组的上市公司为样本,研究政治关联、债务重组对盈余管理的影响。研究得到如下结论:(1)债务重组公司比非债务重组公司具有更高程度的盈余管理水平;债务重组规模越大,盈余管理程度越高;债务重组频率越高,盈余管理程度越高。(2)政治关联与债务重组发生的概率显著正相关;政治关联与债务重组规模显著正相关;政治关联与债务重组频率显著正相关。(3)政治关联与盈余管理显著正相关;政治关联公司债务重组对盈余管理的促进作用高于非政治关联公司。