Controllable Synthesis Of Transition Metal Sulfides And Development Of Electrochemical Sensors

Transition metal sulfides have attracted much attention due to their unique physical and chemical properties,low cost,and easy fabricated.In this paper,M_xS_y?M=Fe,Co,Ni?with special morphology were synthesized by one-pot hydrothermal method using ethanolamine as the structural guidance adjuvants.Then,the best materials were screened out through a series of electrochemical tests?cyclic voltammetry,electrochemical impedance spectroscopy,and amperometry test?,and the best materials were used to construct electrochemical sensor for the detection of hydrogen peroxide,glucose.Furthermore,the results of electrochemical testing show that the catalytic performance of Ni₇S₆ is the best in M_xS_y?M=Fe,Co,Ni?.In order to further improve the catalytic activity of Ni₇S₆ and expand its applications,the Ni₇S₆material was modified,and the prepared modified materials were used to construct electrochemical sensors for the detection of nitrite.The main contents and results are summarized as follows:?1?Controllable preparation of Fe_xS_y and their applicationsIron sulfides with different atomic ratios?Fe_xS_y?were synthesized using FeCl₃·6H₂O and thiourea as precursors,and electrochemical measurements show that the electrochemical performance of Fe S was the best.FeS presents a pomegranate flower-like shape,having a size of about 3?m.The sensor based on Fe S exhibited excellent catalytic activities towards hydrogen peroxide.The sensor had a linear response range between 0.50?M and 20.47 m M with a favorable sensitivity of 36.40?A mM^-1cm^-2and detection limit of 0.15?M for hydrogen peroxide at the optimum operating potential of 0.40 V.?2?Controllable preparation of Co_xS_y and their applicationsCompared the cobalt sulfides with different atomic ratios?Co_xS_y?,screened out the best material was CoS.The CoS presents a tremella-like structure and exhibites excellent catalytic activities towards hydrogen peroxide and glucose.The sensor based on CoS had a linear response range between 5.00?M and 14.82 m M,with a sensitivity of 17.40?A mM^-1cm^-2and a detection limit of 0.15?M for hydrogen peroxide.Meanwhile,the linear range of detection of glucose were 5.00?M-1.10 m M and 1.20 m M-10.20 mM,respectively.The corresponding sensitivity was 139.35?A mM^-1cm^-2and 28.44?A mM^-1cm^-2,respectively.The detection limit was 1.50?M.The two linear range is due to the fact that more and more intermediate species absorb onto the electrode surface with the increasing of glucose concentration,thus limit the following glucose oxidation.?3?Controllable preparation of Ni_xS_y and their applicationsThe best material of Ni_xS_y was screened by electrochemical method,which is the three-dimensional flower-like Ni₇S₆,and it exhibited excellent electrocatalytic activity towards hydrogen peroxide and glucose.The sensor based on Ni₇S₆ had a linear response range between 5.00?M and 20.50 mM,the sensitivity was 37.77?A m M^-1cm^-2,and the detection limit was 0.15?M for hydrogen peroxide.Meanwhile,the sensor also had a linear response range between 5.00?M and 3.70 m M,with sensitivity of 271.80?A mM^-1cm^-2and a detection limit of 0.15?M for glucose.?4?Preparation of Ni₇S₆ modified materials and their applications?a?:Ni₇S₆/MWCNTs composites were prepared by combining Ni₇S₆ with MWCNTs.Ni₇S₆,and Ni₇S₆/MWCNTs were used to construct electrochemical sensors for the detection of nitrite.The sensor based on Ni₇S₆ had a linear response range between 1.00?M and 1.40m M,with a sensitivity of 93.51?A mM^-1cm^-2,and a detection limit of 0.3?M.While the sensor based on Ni₇S₆/MWCNTs had a linear response range between 1.00?M and 4.20 mM,with a sensitivity of 185.04?A mM^-1cm^-2,and a detection limit of 0.3?M.Ni₇S₆/MWCNTs exhibited preferable catalytic activity towards the oxidation of nitrite than that of pure Ni₇S₆,belonging to the synergistic effect between Ni₇S₆ and MWCNTs.?b?:Cobalt doped Ni₇S₆(Ni_7-xCo_xS₆:x=0.5,1.0,1.5,2.0,2.5,3.0,3.5)were synthesized by changing the amount of CoCl₂·6H₂O.Compared the Ni_7-x Co_xS₆,aloe-like Ni_5.5Co_1.5S₆ was screened out for the best material.The sensor based on the Ni_5.5Co_1.5S₆ exhibited excellent catalytic performance for hydrogen peroxide,glucose and nitrite.And Ni_5.5Co_1.5S₆ exhibited preferable catalytic activity than that of pure Ni₇S₆,which due to the synergistic effect between Co and Ni ions in the Ni_5.5Co_1.5S₆.