Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which...Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing(0.852 nm) of graphene oxide(GO), the(002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The ID/IG ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp^2 domains have smaller sizes and larger quantity. The content of sp^2 bonded C in GO(36.93%, molar fraction) increases to 45.48%-72.92%(molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.展开更多
Unique MoS_(2)‐SnS_(2)heterogeneous nanoplates have successfully in‐situ grown on poly(3‐(1‐vinylimidazolium‐3‐yl)propane‐1‐sulfonate)functionalized polypyrrole/graphene oxide(PVIPS/PPy/GO).PVIPS can attract h...Unique MoS_(2)‐SnS_(2)heterogeneous nanoplates have successfully in‐situ grown on poly(3‐(1‐vinylimidazolium‐3‐yl)propane‐1‐sulfonate)functionalized polypyrrole/graphene oxide(PVIPS/PPy/GO).PVIPS can attract heptamolybdate ion(Mo7O246−)and Sn^(4+)as the precursors by the ion‐exchange,resulting in the simultaneous growth of 1T’‐MoS2 and the berndtite‐2T‐type hexagonal SnS_(2)by the interfacial induced effect of PVIPS.The obtained MoS_(2)‐SnS_(2)/PVIPS/PPy/GO can serve as electrocatalysts,exhibiting good NRR performance by the synergistic effect.The semi‐conducting SnS_(2)would limit the surface electron accessibility for suppressing HER process of 1T’‐MoS_(2),while metallic 1T’‐MoS_(2)might efficiently improve the NRR electroactivity of SnS_(2)by the creation of Mo‐Sn‐Sn trimer catalytic sites.Otherwise,the irreversible crystal phase transition has taken place during the NRR process.Partial 1T’‐MoS_(2)and SnS_(2)have electrochemically reacted with N_(2),and irreversibly converted into Mo^(2)N and SnxNz due to the formation of Mo−N and Sn−N bonding,meanwhile,partial SnS_(2) has been irreversibly evolved into SnS due to the reduction by the power source in the electrochemical system.It would put forward a new design idea for optimizing the preparation method and electrocatalytic activity of transition metal dichalcogenides.展开更多
Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Dev...Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Development and design of high-performance NRR electrocatalysts are indispensable to achieve the goal.In this work,a strongly coupled hybrid of nano-Fe3O4 with reduced graphene oxide(rGO)is synthesized via an in situ redox hydrothermal approach,and the synthesized Fe_(3)O_(4)@r GO hybrid has excellent activity,selectivity,and stability as an NRR catalyst.The NH_(3) yield rate of 28.01μg h^(-1)mg^(-1)at-0.3 V and the Faradaic efficiency(FE)of 19.12%at-0.1 V are obtained in 0.1 M Na_(2)SO_(4) solutions at ambient conditions.The superior NRR performance is attributed to the chemical coupling effect between r GO and nano-Fe_(3)O_(4) particles,which leads to the enhancement of the binding affinity to N_(2) molecules,improvement of the conductivity,and lowering the free energy of reaction for the limiting reaction step.This work provides a facile route in fabricating hybrid NRR catalysts with superior performance and shed lights on the reaction mechanism with theoretical mechanistic calculations.展开更多
基金Project(51274248)supported by the National Natural Science Foundation of ChinaProjects(2015DFR50580,2013DFA31440)supported by the International Scientific and Technological Cooperation Program of China
文摘Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing(0.852 nm) of graphene oxide(GO), the(002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The ID/IG ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp^2 domains have smaller sizes and larger quantity. The content of sp^2 bonded C in GO(36.93%, molar fraction) increases to 45.48%-72.92%(molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.
文摘Unique MoS_(2)‐SnS_(2)heterogeneous nanoplates have successfully in‐situ grown on poly(3‐(1‐vinylimidazolium‐3‐yl)propane‐1‐sulfonate)functionalized polypyrrole/graphene oxide(PVIPS/PPy/GO).PVIPS can attract heptamolybdate ion(Mo7O246−)and Sn^(4+)as the precursors by the ion‐exchange,resulting in the simultaneous growth of 1T’‐MoS2 and the berndtite‐2T‐type hexagonal SnS_(2)by the interfacial induced effect of PVIPS.The obtained MoS_(2)‐SnS_(2)/PVIPS/PPy/GO can serve as electrocatalysts,exhibiting good NRR performance by the synergistic effect.The semi‐conducting SnS_(2)would limit the surface electron accessibility for suppressing HER process of 1T’‐MoS_(2),while metallic 1T’‐MoS_(2)might efficiently improve the NRR electroactivity of SnS_(2)by the creation of Mo‐Sn‐Sn trimer catalytic sites.Otherwise,the irreversible crystal phase transition has taken place during the NRR process.Partial 1T’‐MoS_(2)and SnS_(2)have electrochemically reacted with N_(2),and irreversibly converted into Mo^(2)N and SnxNz due to the formation of Mo−N and Sn−N bonding,meanwhile,partial SnS_(2) has been irreversibly evolved into SnS due to the reduction by the power source in the electrochemical system.It would put forward a new design idea for optimizing the preparation method and electrocatalytic activity of transition metal dichalcogenides.
基金Sichuan Science and Technology Program(2018GZ0459)Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003)the Fundamental Research Funds for the Central Universities(WUT:2020Ⅲ029)
文摘Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Development and design of high-performance NRR electrocatalysts are indispensable to achieve the goal.In this work,a strongly coupled hybrid of nano-Fe3O4 with reduced graphene oxide(rGO)is synthesized via an in situ redox hydrothermal approach,and the synthesized Fe_(3)O_(4)@r GO hybrid has excellent activity,selectivity,and stability as an NRR catalyst.The NH_(3) yield rate of 28.01μg h^(-1)mg^(-1)at-0.3 V and the Faradaic efficiency(FE)of 19.12%at-0.1 V are obtained in 0.1 M Na_(2)SO_(4) solutions at ambient conditions.The superior NRR performance is attributed to the chemical coupling effect between r GO and nano-Fe_(3)O_(4) particles,which leads to the enhancement of the binding affinity to N_(2) molecules,improvement of the conductivity,and lowering the free energy of reaction for the limiting reaction step.This work provides a facile route in fabricating hybrid NRR catalysts with superior performance and shed lights on the reaction mechanism with theoretical mechanistic calculations.
