| Supercapacitor, metal-air battery, electrochemical water spliting are three most promising solutions for current energy problems. But due to the lack of inexpensive and efficient energy storage/convresion electrode material their potential cannot be realized. Fe-based and Mn-based functional material have long been the interest of research and application, however the study of their properties have focused more on tuning of their morphology and structure while little on their composition. In this article, six series of Fe-based and Mn-based ternary metal sulfides with different elemental composition have been prepared using fumed silica as the sacrificial template.The different kinetics of reactive species in hot alkaline solution generate competing reaction effects, leading to the formation of metal hydroxide on template support, the sulfide ion exchange and the etching of template taken place in sequence. This preparation method is named sacrificial template-competing sulfication (STCS) method and is advantageous for its facile preparation and efficient separation. Using the STCS method, cobalt sulfides with stable nanosheet-like morphology can be prepared. With a total metal ion concentration of 6 mmol·mL/1 and a sulfur dose of 30mg·mL-1, products of cobalt sulfides with sacrificial template enjoy a 60% enlargement of their electrochemical active surface area compared with products prepared without template. The optimized reaction parameters are a total metal ion concentration of 0.3 mmol-mL'1 and a sulfur dose of 10mg·mL-1.Nanosheet-like (Cu2Fe)Sx with three-dimensional struction are prepared using STCS method under the optimized conditions. The prepared material showed a specific capacitance of 437F·g-1 at 1A·g-1,which is relatively superior among the reported values of copper sulfides. At the same time, the material have a high energy density of 28Wh kg-1 at a power density of 1000W·kg-1.Fe-based ternary metal sulfides Ni-Fe-S and Cu-Fe-S showed good HER (Hydrogen Reduction Reaction) catalytic performance, within the composition range in this work, larger Cu or Ni composition ratios favor the enhancement of HER catalytic activity. Among the catalyst material tested for HER application (Ni2Fe)Sx showed a relatively good catalytic activity with a small overpotential of 476mV under the polarization current density of 10mA·cm-2 and a small Tafel slope of 175mV dec-1 at high overpotential region. Calculated according to Arrhenius equation, this material has a activation energy of 12kJ·mol-1 for HER reaction. Off-state chronopotentiometry and cyclic voltammetry revealed the HER undergone Volmer-Heyrovsky pathway and the electrochemical stripping step is the rate-limiting step of hydrogen evolution reaction.Mn-based Ternary metal sulfide Cu-Mn-S, Co-Mn-S and Ni-Mn-S showed ORR (Oxygen Reduction Reaction) catalytic activity. Within the composition range in this work, higher Co ratios improved ORR and OER (Oxygen Reduction Reaction) catalytic activity. Amony these Mn-based materials, (Co2Mn)Sx showed superior ORR/OER bifunctional catalytic performance and anti-poisoning ability towards methanol and carbon monoxide. (Co2Mn)Sx showed an overall ORR/OER overpotential of 0.59V(calculated by onset potential differences) which is smaller than that of commercialized Pt/C. At an overpotential of 500mV, (Co2Mn)Sx showed a larger oxygen evolution current dentsity, which was approximately 6.3 times that of commercialized Pt/C. |
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