| Environmental pollution and energy shortage are regarded as major challenges by all countries today.H2 is regarded as the ideal energy source in the future,and electrocatalytic production of hydrogen is an effective method.At present,platinum and other precious metals and their com-pounds are considered to be the most efficient electrocatalysts for hydrogen evolution reaction(HER).However,the high price and the scarcity of re-serves hinder its commercial application.Therefore,the development of cheap,high activity and good stability of new non noble metal catalysts is an important means to achieve electrocatalytic hydrogen evolution.In this paper,molybdenum disulfide(MoS2)layered sulfide as the main body,to build multi-level nanocomposites,to study the structural design and con-struction methods.In addition,the edge interface has lower interface re-sistance,and more active sites are created to enhance hydrogen evolution activity by enhancing edge effect and electrical properties.In the presence of heavy metals ions in biological system could induce undesired chemical transformation of proteins and enzymes that eventually affects their func-tional activities which lead to chronic poisoning due to an accumulation in certain organs.In particular,Pb2+ion could directly imperil to the human brain cells performance,causing fetal neuro-developmental delay,elderly dementia and brain death.In our previous work,it has been proved that the potential electrochemical sensors based on g-C3N4 in the detection of bio-logical and environmental hormone molecules.In addition,heavy metal ions exist in the biological system as pollu-tants.The accumulation of heavy metal ions in some organs can induce unexpected chemical transformation of proteins and enzymes,and ulti-mately affect their functional activities,leading to chronic poisoning of hu-man body.Pb2+,in particular,can directly affect the function of human brain cells,leading to fetal nerve retardation,Alzheimer's disease and brain death.In this paper,based on g-C3N4,a sulfur doped Pb2+sensor is con-structed.The research results are as follows:1.A new type of sulfur-doped graphite carbonitride nanosheets was successfully prepared by thermal polycondensation method,and Pb2+elec-trochemical sensor(S-g-C3N4/GCE).DFT calculations confirmed that strong electrochemical response of Pb2+is boost through the interaction of S-Pb bonds between S-g-C3N4 and Pb2+(Milliken charges of approxi-mately-0.5975 and 0.5241 a.u.)at the interface,respectively.S-g-C3N4/GCE has high sensitivity and selectivity to Pb2+which the detection linear range is 7.5×10-8?2.5×10-6 mol·L-1 and 2.5×10-6?1×10-3mol·L-1with the minimum detection limit is 3.0×10-9 mol·L-1(S/N=3).In practical applications,we detect Pb2+in lake water and mineral sample with the re-covery rate is 88-103%.Therefore,S-g-C3N4/GCE can be used as a sensi-tive and selective electrochemical sensor for reliable detection of heavy metal ions in domestic sewage and industrial wastewater.2.The composite nano materials(MoS2/U-g-C3N4)with U-g-C3N4 as the substrate and MoS2 as the active material were prepared by one-step microwave hydrothermal method.By enhancing the edge effect,MoS2/U-g-C3N4)composite nano materials exposed a large number of active sites,its specific surface area and electrical conductivity were significantly im-proved.The overpotential was 152 m V at 10 m A·cm-2,and the Tafel slope was 54 m V·dec-1.However,the difference between the LSV curve meas-ured after 9000 cycles of CV and the original test results was only 20%,showed excellent HER catalytic activity and good stability;3.FeS2/MoS2/g-C3N4 nanocomposites,g-C3N4 as substrate and MoS2and FeS2 as active materials,were synthesized by one-step microwave hy-drothermal method.The electron transport ability of MoS2/g-C3N4 nano-composites was improved by the doping of FeS2.When the current density is 10 m A·cm-2,the over potential is reduced to 121 m V,and the Tafel slope is also reduced to 49.5 m V·dec-1.When the overpotential is set to?=121m V and the chronoamperometric current method is continually test for 25h,the test results and the first LSV curve remain unchanged at the over-potential of 10 m A·cm-2.The table shows low over potential,low Tafel slope and good stability.At?=300 m V,the turnover frequency(TOF)of FeS2/MoS2/g-C3N4 is 8 s-1,which is 53.33 folds of FeS2,8.42 times of MoS2 and 7.41 times of MoS2/g-C3N4,respectively.It shows that the dop-ing of FeS2 makes the number and quality of active sites of MoS2/g-C3N4nanocomposites significantly improved,and the electron transfer rate also significantly improved.This work provides a new material for the study of new electrocatalytic hydrogen evolution materials;... |
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