Unveiling the chemistry behind the electrolytic production of hydrogen peroxide by oxygenated carbon

Oxygenated carbon materials exhibit outstanding electrocatalytic performance in the production of hydrogen peroxide(H2O2)through a two-electron oxygen reduction reaction.The nature of the active functional group and underlying reaction mechanism,however,remain unclear.Here,a comprehensive workflow was established to identify the active sites from the numerous possible structures.The common hydroxyl group at the notched edge demonstrates a key role in the two-electron process.The local chemical environment weakens the binding of OOH intermediate to substrate while enhancing interaction with solution,thereby promoting the H_(2)O_(2)production.With increasing pH,the intramolecular hydrogen bond between OOH intermediate and hydroxyl decreases,facilitating OOH desorption.Furthermore,the rise in selectivity with increasing potential stems from the suppression of the four-electron process.The active site was further validated through experiments.Guided by theoretical understanding,optimal performance was achieved with high selectivity(>95%)and current density(2.06 mA/cm^(2))in experiment.

Oxidation Evolution and Activity Origin of N-Doped Carbon in the Oxygen Reduction Reaction

N-doped carbon materials,with their applications as electrocatalysts for the oxygen reduction reaction(ORR),have been extensively studied.However,a negletcted fact is that the operating potential of the ORR is higher than the theoretical oxida-tion potential of carbon,possibly leading to the oxidation of carbon materials.Consequently,the infl uence of the structural oxidation evolution on ORR performance and the real active sites are not clear.In this study,we discover a two-step oxida-tion process of N-doped carbon during the ORR.The fi rst oxidation process is caused by the applied potential and bubbling oxygen during the ORR,leading to the oxidative dissolution of N and the formation of abundant oxygen-containing functional groups.This oxidation process also converts the reaction path from the four-electron(4e)ORR to the two-electron(2e)ORR.Subsequently,the enhanced 2e ORR generates oxidative H_(2)O_(2),which initiates the second stage of oxidation to some newly formed oxygen-containing functional groups,such as quinones to dicarboxyls,further diversifying the oxygen-containing functional groups and making carboxyl groups as the dominant species.We also reveal the synergistic eff ect of multiple oxygen-containing functional groups by providing additional opportunities to access active sites with optimized adsorption of OOH*,thus leading to high effi ciency and durability in electrocatalytic H_(2)O_(2) production.

Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,China.This research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this region.The experimental site was divided into drip and flood irrigation zones.The irrigation schedules of this study aligned with the local commonly used irrigation schedule.We employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation methods.From May to September in 2020 and 2021,two sets of repeated experiments were conducted.In each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize crop.During each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)exchange.During each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were measured.The results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting trend.Notably,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize plants.Consequently,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utilization efficiency,irrespective of the irrigation method.Notably,drip irrigation displayed superior light use efficiency compared with flood irrigation.The final yield results corroborated these findings,indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation.The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District.This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

High-throughput microfluidic production of carbon capture microcapsules:fundamentals,applications,and perspectives

In the last three decades,carbon dioxide(CO_(2)) emissions have shown a significant increase from various sources.To address this pressing issue,the importance of reducing CO_(2) emissions has grown,leading to increased attention toward carbon capture,utilization,and storage strategies.Among these strategies,monodisperse microcapsules,produced by using droplet microfluidics,have emerged as promising tools for carbon capture,offering a potential solution to mitigate CO_(2) emissions.However,the limited yield of microcapsules due to the inherent low flow rate in droplet microfluidics remains a challenge.In this comprehensive review,the high-throughput production of carbon capture microcapsules using droplet microfluidics is focused on.Specifically,the detailed insights into microfluidic chip fabrication technologies,the microfluidic generation of emulsion droplets,along with the associated hydrodynamic considerations,and the generation of carbon capture microcapsules through droplet microfluidics are provided.This review highlights the substantial potential of droplet microfluidics as a promising technique for large-scale carbon capture microcapsule production,which could play a significant role in achieving carbon neutralization and emission reduction goals.

The multiple roles of crop structural change in productivity,nutrition and environment in China:A decomposition analysis

China's crop structure has undergone significant changes in the last two decades since 2000,with an increase in the share of cereals,vegetables,and fruit,squeezing out other crops.As a result,land productivity,nutrient supply,and carbon emissions have changed.How to reallocate limited farmland among crops to achieve the multiple goals of agrifood systems becomes an important issue.This study explores the sources of land productivity and nutrition supply growth and carbon emissions reduction,and identifies the multiple roles of crop structural change from 2003 to 2020 based on a decomposition analysis.The results reveal that the growth within crops is still the primary driver in land productivity and nutrition supply and the reduction in carbon emissions.However,structural change also plays various roles at different periods.From 2003 to 2010,crop structural change increased the total calorie supply but lowered land productivity and contributed at least 70%of the total growth of carbon emissions.The crop structure was relatively stable,and their effects were modest from 2010 to 2015.From 2015 to 2020,the crop structural change began to play a greater role and generate synergistic effects in improving land productivity,micronutrient supply,and reducing carbon emissions,contributing to approximately a quarter of the growth of land productivity and 30%of total carbon emissions reduction.These results suggest that strategies for crop structural change should comprehensively consider its multiple impacts,aiming to achieve co-benefits while minimizing trade-offs.

Pore structure and oxygen content design of amorphous carbon toward a durable anode for potassium/sodium-ion batteries

Both sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs)are considered as promising candidates in grid-level energy storage devices.Unfortunately,the larger ionic radii of K+and Na+induce poor diffusion kinetics and cycling stability of carbon anode materials.Pore structure regulation is an ideal strategy to promote the diffusion kinetics and cyclic stability of carbon materials by facilitating electrolyte infiltration,increasing the transport channels,and alleviating the volume change.However,traditional pore-forming agent-assisted methods considerably increase the difficulty of synthesis and limit practical applications of porous carbon materials.Herein,porous carbon materials(Ca-PC/Na-PC/K-PC)with different pore structures have been prepared with gluconates as the precursors,and the amorphous structure,abundant micropores,and oxygen-doping active sites endow the Ca-PC anode with excellent potassium and sodium storage performance.For PIBs,the capacitive contribution ratio of Ca-PC is 82%at 5.0 mV s^(-1) due to the introduction of micropores and high oxygen-doping content,while a high reversible capacity of 121.4 mAh g^(-1) can be reached at 5 A g^(-1) after 2000 cycles.For SIBs,stable sodium storage capacity of 101.4 mAh g^(-1) can be achieved at 2 A g^(-1) after 8000 cycles with a very low decay rate of 0.65%for per cycle.This work may provide an avenue for the application of porous carbon materials in the energy storage field.

Engineering oxygen vacancies on Tb-doped ceria supported Pt catalyst for hydrogen production through steam reforming of long-chain hydrocarbon fuels

Steam reforming of long-chain hydrocarbon fuels for hydrogen production has received great attention for thermal management of the hypersonic vehicle and fuel-cell application.In this work,Pt catalysts supported on CeO_(2)and Tb-doped CeO_(2)were prepared by a precipitation method.The physical structure and chemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction,scanning electron microscopy,transmission electron microscopy,Raman spectroscopy,H_(2)temperature programmed reduction,and X-ray photoelectron spectroscopy.The results show that Tb-doped CeO_(2)supported Pt possesses abundant surface oxygen vacancies,good inhibition of ceria sintering,and strong metal-support interaction compared with CeO_(2)supported Pt.The catalytic performance of hydrogen production via steam reforming of long-chain hydrocarbon fuels(n-dodecane)was tested.Compared with 2Pt/CeO_(2),2Pt/Ce_(0.9)Tb_(0.1)O_(2),and 2Pt/Ce_(0.5)Tb_(0.5)O_(2),the 2Pt/Ce_(0.7)Tb_(0.3)O_(2)has higher activity and stability for hydrogen production,on which the conversion of n-dodecane was maintained at about 53.2%after 600 min reaction under 700℃at liquid space velocity of 9 ml·g^(-1)·h^(-1).2Pt/CeO_(2)rapidly deactivated,the conversion of n-dodecane was reduced to only 41.6%after 600 min.

Rational design of vitamin C/defective carbon van der Waals heterostructure for enhanced activity,durability and storage stability toward oxygen reduction reaction

Metal-free defective carbon materials with abundant active sites have been widely studied as low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts in metal-air batteries.However,the active sites in defective carbon are easily subjected to serious oxidation or hydroxylation during ORR or storage,leading to rapid degradation of activity.Herein,we design a van der Waals heterostructure comprised of vitamin C(VC)and defective carbon(DC)to not only boost the activity but also enhance the durability and storage stability of the DC-VC electrocatalyst.The formation of VC van der Waals between DC and VC is demonstrated to be an effective strategy to protect the defect active sites from oxidation and hydroxylation degradation,thus significantly enhancing the electrochemical durability and storage anti-aging performance.Moreover,the DC-VC van der Waals can reduce the reaction energy barrier to facilitate the ORR.These findings are also confirmed by operando Fourier transform infrared spectroscopy and density functional theory calculations.It is necessary to mention that the preparation of this DC-VC electrocatalyst can be scaled up,and the ORR performance of the largely produced electrocatalyst is demonstrated to be very consistent.Furthermore,the DC-VC-based aluminum-air batteries display very competitive power density with good performance maintenance.

Potentials and Challenges of Carbon Knowledge Graph in Sustainable Textile Production for Carbon Traceability:A Review

Textile production has received considerable attention owing to its significance in production value,the complexity of its manufacturing processes and the extensive reach of its supply chains.However,textile industry consumes substantial energy and materials and emits greenhouse gases that severely harm the environment.In addressing this challenge,the concept of sustainable production offers crucial guidance for the sustainable development of the textile industry.Low-carbon manufacturing technologies provide robust technical support for the textile industry to transition to a low-carbon model by optimizing production processes,enhancing energy efficiency and minimizing material waste.Consequently,low-carbon manufacturing technologies have gradually been implemented in sustainable textile production scenarios.However,while research on low-carbon manufacturing technologies for textile production has advanced,these studies predominantly concentrate on theoretical methods,with relatively limited exploration of practical applications.To address this gap,a thorough overview of carbon emission management methods and tools in textile production,as well as the characteristics and influencing factors of carbon emissions in key textile manufacturing processes is presented to identify common issues.Additionally,two new concepts,carbon knowledge graph and carbon traceability,are introduced,offering strategic recommendations and application directions for the low-carbon development of sustainable textile production.Beginning with seven key aspects of sustainable textile production,the characteristics of carbon emissions and their influencing factors in key textile manufacturing process are systematically summarized.The aim is to provide guidance and optimization strategies for future emission reduction efforts by exploring the carbon emission situations and influencing factors at each stage.Furthermore,the potential and challenges of carbon knowledge graph technology are summarized in achieving carbon traceability,and several research ideas and suggestions are proposed.

Tuning the crystalline and electronic structure of ZrO_(2)via oxygen vacancies and nano-structuring for polysulfides conversion in lithium-sulfur batteries

The recent emergence of tetragonal phases zirconium dioxide(ZrO_(2))with vacancies has generated significant interest as a highly efficient and stable electrocatalyst with potential applications in trapping polysulfides and facilitating rapid conversion in lithium-sulfur batteries(LSBs).However,the reduction of ZrO_(2)is challenging,even under strong reducing atmospheres at high temperatures and pressures.Consequently,the limited presence of oxygen vacancies results in insufficient active sites and reaction interfaces,thereby hindering practical implementation.Herein,we successfully introduced abundant oxygen vacancies into ZrO_(2)at the nanoscale with the help of carbon nanotubes(CNTs-OH)through hydrogen-etching at lower temperatures and pressures.The introduced oxygen vacancies on ZrO_(2-x)/CNTs-OH can effectively rearrange charge distribution,enhance sulfiphilicity and increase active sites,contributing to high ionic and electronic transfer kinetics,strong binding energy and low redox barriers between polysulfides and ZrO_(2-x).These findings have been experimentally validated and supported by theory calculations.As a result,LSBs assembled with the ZrO_(2-x)/CNTs-OH modified separators demonstrate excellent rate performance,superior cycling stability,and ultra-high sulfur utilization.Especially,at high sulfur loading of 6 mg cm^(-2),the area capacity is still up to 6.3 mA h cm^(-2).This work provides valuable insights into the structural and functional optimization of electrocatalysts for batteries.

Impact of digital economy development on carbon productivity:An empirical analysis based on threshold effect and spatial spillover effect

Utilizing provincial panel data from 2014 to 2020,this study employs a fixed effect model,a threshold effect model,and a spatial lag model to empirically examine the correlation between digital economic development and carbon productivity.The findings indicate that digital economic development significantly contributes to the enhancement of carbon productivity in the long term.Furthermore,through instrumental variable method,replacement of explanatory variables and other methods to test its endogeneity and stability,the results remain robust.In terms of regional heterogeneity,the impact of digital economic development on carbon productivity is less pronounced in the central and western regions compared to the eastern region.Additionally,further investigation reveals that industrial structure upgrading and science and technology investment level exhibit different threshold effects on the influence of digital economy development level on carbon productivity.Moreover,there is a significant spatial spillover effect of digital economy development on carbon productivity with H-H and L-L agglomeration spatial correlation.

Response to the Lomagundi-Jatuli Event in the southwestern margin of the Yangtze Plate:Evidence from the carbon and oxygen isotopes of the Paleoproterozoic Yongjingshao Formation

The Lomagundi-Jatuli Event(LJE)refers to the significant positive carbon isotope excursion in seawater constituents that occurred immediately after the increase in atmospheric oxygen content during the Paleoproterozoic(2.22-2.06 Ga).Theδ^(13)C values of 46 dolostone samples collected from the Paleoproterozoic Yongjingshao Formation varied in the range of 0.05‰-4.95‰(V-PDB;maximum:4.95‰)in this study,which may be related to the multicellular eukaryotes in the Liangshan Formation in the Yimen Group.They are much higher than theδ^(13)C values of marine carbonates(-1.16‰on average).Theδ^(13)C values of other formations in the Paleoproterozoic Yimen Group are negative.The notable positive carbon isotope anomalies of the Yongjingshao Formation indicate the response to the LJE at the southwestern margin of the Yangtze Block,which is reported for the first time.Furthermore,they are comparable to theδ^(13)C values of carbonates in the Dashiling Formation of the Hutuo Group in the Wutaishan area in the North China Craton,the Wuzhiling Formation of the Songshan Group in the Xiong'er area,Henan Province,and the Dashiqiao Formation of the Liaohe Group in the Guanmenshan area,Liaoning Province.Therefore,it can be further concluded that the LJE is a global event.This study reveals that LJE occurred in Central Yunnan at 2.15-2.10 Ga,lasting for about 50 Ma.The macro-columnar,bean-shaped,and microfilament fossils and reticular ultramicrofossils of multicellular eukaryotes in this period were discovered in the Liangshan Formation of the Yimen Group.They are the direct cause for the LJE and are also the oldest paleontological fossils ever found.The major events successively occurring in the early stage of the Earth include the Great Oxygenation Event(first occurrence),the global Superiortype banded iron formations(BIFs),the Huronian glaciation,the Great Oxygenation Event(second occurrence),the explosion of multicellular eukaryotes,the positive carbon isotope excursion,and the global anoxic and selenium-rich sedimentary event.The authors think that the North China Craton and the Yangtze Craton were possibly in different tectonic locations of the same continental block during the Proterozoic.

Co/CoO heterojunction rich in oxygen vacancies introduced by O2 plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc-air battery

Herein,Co/CoO heterojunction nanoparticles(NPs)rich in oxygen vacancies embedded in mesoporous walls of nitrogen-doped hollow carbon nanoboxes coupled with nitrogen-doped carbon nanotubes(P-Co/CoOV@NHCNB@NCNT)are well designed through zeolite-imidazole framework(ZIF-67)carbonization,chemical vapor deposition,and O_(2) plasma treatment.As a result,the threedimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P-Co/CoOV@NHCNB@NCNT,and they display exceedingly good electrocatalytic performance for oxygen reduction reaction(ORR,halfwave potential[EORR,1/2=0.855 V vs.reversible hydrogen electrode])and oxygen evolution reaction(OER,overpotential(η_(OER,10)=377mV@10mA cm^(−2)),which exceeds that of the commercial Pt/C+RuO_(2) and most of the formerly reported electrocatalysts.Impressively,both the aqueous and flexible foldable all-solid-state rechargeable zinc-air batteries(ZABs)assembled with the P-Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long-term cycling stability.First-principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity,reduces reaction energy barriers,and accelerates reaction kinetics rates.This work opens up a new avenue for the facile construction of highly active,structurally stable,and cost-effective bifunctional catalysts for ZABs.

The role of reactive oxygen species in gastric cancer

Gastric cancer(GC)ranks fifth in cancer incidence and fourth in cancer-related mortality worldwide.Reactive oxygen species(ROS)are highly oxidative oxygen-derived products that have crucial roles in cell signaling regulation and maintaining internal balance.ROS are closely associated with the occurrence,development,and treatment of GC.This review summarizes recent findings on the sources of ROS and the bidirectional regulatory effects on GC and discusses various treatment modalities for GC that are related to ROS induction.In addition,the regulation of ROS by natural small molecule compounds with the highest potential for development and applications in anti-GC research is summarized.The aim of the review is to accelerate the clinical application of modulating ROS levels as a therapeutic strategy for GC.

Retaining the self-released chalcogenate at reconstructed cobalt sites by self-transformed carbonate regulation for boosted oxygen evolution

The in-situ generated oxyanions at electrochemically reconstructed catalysts from metal-based nonoxide compounds have been proven to significantly accelerate oxygen evolution reaction(OER)kinetics.However,it remains a challenge to retain these self-released oxyanions at reconstructed catalysts,hindering its utilization as a tool to develop efficient OER catalysts.Here,we demonstrate a versatile selftransformed carbonate regulation strategy to efficiently retain the self-released chalcogenate at Co oxyhydroxides reconstructed from carbon-incorporated Co selenides under OER conditions.These selftransformed CO_(3)^(2-)can induce electron accumulation and narrow d bond at Co sites to facilitate the Co3d-O 2p orbital hybridization between Co sites and SeO_(x)^(2-)for enhanced SeO_(x)^(2-)retention,which can accelerate the rate-limiting step for^(*)OOH formation during OER.Relative to CoOOH-SeO_(x)^(2-)with limited SeO_(x)^(2-)residues,CoOOH-CO_(3)^(2-)/SeO_(x)^(2-)with elevated SeO_(x)^(2-)retention by CO_(3)^(2-)regulation exhibited a 5.6-fold increase in current density and a remarkable lower Tafel slope towards OER.This strategy paves a rational avenue to design efficient catalysts for electrooxidation reactions through finely regulating self-released oxyanions at reconstructed structures.

Diamond-Like Carbon Depositing on the Surface of Polylactide Membrane for Prevention of Adhesion Formation During Tendon Repair

Post-traumatic peritendinous adhesion presents a significant challenge in clinical medicine.This study proposes the use of diamond-like carbon(DLC)deposited on polylactic acid(PLA)membranes as a biophysical mechanism for anti-adhesion barrier to encase ruptured tendons in tendon-injured rats.The results indicate that PLA/DLC composite membrane exhibits more efficient anti-adhesion effect than PLA membrane,with histological score decreasing from 3.12±0.27 to 2.20±0.22 and anti-adhesion effectiveness increasing from 21.61%to 44.72%.Mechanistically,the abundant C=O bond functional groups on the surface of DLC can reduce reactive oxygen species level effectively;thus,the phosphorylation of NF-κB and M1 polarization of macrophages are inhibited.Consequently,excessive inflammatory response augmented by M1 macrophage-originated cytokines including interleukin-6(IL-6),interleukin-1β(IL-1β),and tumor necrosis factor-α(TNF-α)is largely reduced.For biocompatibility evaluation,PLA/DLC membrane is slowly absorbed within tissue and displays prolonged barrier effects compared to traditional PLA membranes.Further studies show the DLC depositing decelerates the release of degradation product lactic acid and its induction of macrophage M2 polarization by interfering esterase and PLA ester bonds,which further delays the fibrosis process.It was found that the PLA/DLC membrane possess an efficient biophysical mechanism for treatment of peritendinous adhesion.

Evolution of the porous structure for phosphoric acid etching carbon as cathodes in Li–O_(2) batteries:Pyrolysis temperature-induced characteristics changes

Although biomass-derived carbon(biochar)has been widely used in the energy field,the relation between the carbonization condition and the physical/chemical property of the product remains elusive.Here,we revealed the carbonization condition's effect on the morphology,surface property,and electrochemical performance of the obtained carbon.An open slit pore structure with shower-puff-like nanoparticles can be obtained by finely tuning the carbonization temperature,and its unique pore structure and surface properties enable the Li–O_(2) battery with cycling longevity(221 cycles with 99.8%Coulombic efficiency at 0.2 mA cm^(−2) and controlled discharge–charge depths of 500 mAh g^(−1))and high capacity(16,334 mAh g^(−1) at 0.02 mA cm^(−2)).This work provides a greater understanding of the mechanism of the biochar carbonization procedure under various pyrolysis conditions,paving the way for future study of energy storage devices.

Tuning the cross-linked structure of basic poly(ionic liquid)to develop an efficient catalyst for the conversion of vinyl carbonate to dimethyl carbonate

Dimethyl carbonate(DMC)is a crucial chemical raw material widely used in organic synthesis,lithiumion battery electrolytes,and various other fields.The current primary industrial process employs a conventional sodium methoxide basic catalyst to produce DMC through the transesterification reaction between vinyl carbonate and methanol.However,the utilization of this catalyst presents several challenges during the process,including equipment corrosion,the generation of solid waste,susceptibility to deactivation,and complexities in separation and recovery.To address these limitations,a series of alkaline poly(ionic liquid)s,i.e.[DVBPIL][PHO],[DVCPIL][PHO],and[TBVPIL][PHO],with different crosslinking degrees and structures,were synthesized through the construction of cross-linked polymeric monomers and functionalization.These poly(ionic liquid)s exhibit cross-linked structures and controllable cationic and anionic characteristics.Research was conducted to investigate the effect of the cross-linking degree and structure on the catalytic performance of transesterification in synthesizing DMC.It was discovered that the appropriate cross-linking degree and structure of the[DVCPIL][PHO]catalyst resulted in a DMC yield of up to 80.6%.Furthermore,this catalyst material exhibited good stability,maintaining its catalytic activity after repeated use five times without significant changes.The results of this study demonstrate the potential for using alkaline poly(ionic liquid)s as a highly efficient and sustainable alternative to traditional catalysts for the transesterification synthesis of DMC.

Origin of the Dashuigou independent tellurium deposit at Qinghai–Xizang Plateau: constraints from the light stable isotopes C, O, and H

By studying the light isotopic compositions of carbon,oxygen,and hydrogen,combined with previous research results on the ore-forming source of the deposit,the authors try to uncover its metallogenic origin.The δ^(18)O and δ^(13)C isotope signatures of dolomite samples vary between 10.2 and 13.0‰,and between−7.2 and−5.2‰,respectively,implying that the carbon derives from the upper mantle.δD and δ^(18) O of quartz,biotite,and muscovite from diff erent ore veins of the deposit vary between−82 and−59‰,and between 11.6 and 12.4‰,respectively,implying that the metallogenic solutions are mainly magmatic.According to the relevant research results of many isotope geologists,the fractionation degree of hydrogen isotopes increases as the depth to the Earth’s core increases,and the more diff erentiated the hydrogen isotopes are,the lower their values will be.In other words,mantle-derived solutions can have extremely low hydrogen isotope values.This means that the δD‰ value−134 of the pyrrhotite sample numbered SD-34 in this article may indicate mantle-derived oreforming fl uid of the deposit.The formation of the Dashuigou tellurium deposit occurred between 91.71 and 80.19 Ma.

Sulfur doped iron-nitrogen-hard carbon nanosheets as efficient and robust noble metal-free catalysts for oxygen reduction reaction in PEMFC

Transition metal-nitrogen-carbon(M-N-C)as a promising substitute for the conventional noble metalbased catalyst still suffers from low activity and durability for oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).To tackle the issue,herein,a new type of sulfur-doped ironnitrogen-hard carbon(S-Fe-N-HC)nanosheets with high activity and durability in acid media were developed by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymerizing two monomers of 2,5-thiophene dicarboxylic acid(TDA)as S source and 1,8-diaminonaphthalene(DAN)as N source via an amination reaction.The as-synthesized S-Fe-N-HC features highly dispersed atomic Fe Nxmoieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals,which is distinguished from the majority of M-N-C with soft or graphitic carbon structures.These unique characteristics endow S-Fe-N-HC with high ORR activity and outstanding durability in 0.5 M H_(2)SO_(4).Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 m V after 30,000 cycles.Meanwhile,its practical PEMFC performance is a maximum power output of 628.0 mW cm^(-2)and a slight power density loss is 83.0 m W cm^(-2)after 200-cycle practical operation.Additionally,theoretical calculation shows that the activity of Fe Nxmoieties on ORR can be further enhanced by sulfur doping at meta-site near FeN_(4)C.These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts,providing a new guidance for developing advanced M-N-C catalysts for ORR.