Abstract
Layered two-dimensional titanium carbide (Ti3C2Tx), as an outstanding MXene member, has captured increasing attention in supercapacitor applications due to its excellent chemical and physical properties. However, the low gravimetric capacitance of Ti3C2Tx restricts its rapid development in such applications. Herein, this work demonstrates an effective and facile hydrothermal approach to synthesize nitrogen doped intercalation TiO2/TiN/Ti3C2Tx with greatly improved gravimetric capacitance and excellent cycling stability. The hexamethylenetetramine (C6H12N4) in hydrothermal environment acted as the nitrogen source and intercalants, while the Ti3C2Tx itself was the titanium source of TiO2 and TiN. We tested the optimized nitrogen doped intercalation TiO2/TiN/Ti3C2Tx electrodes in H2SO4, Li2SO4, Na2SO4, LiOH and KOH electrolytes, respectively. The electrode in H2SO4 electrolyte delivered the best electrochemical performance with high gravimetric capacitance of 361 F g−1 at 1 A g−1 and excellent cycling stability of 85.8% after 10,000 charge/discharge cycles. A systematic study of material characterization combined with the electrochemical performances disclosed that TiO2/TiN nanoparticles, the introduction of nitrogen and the NH4+ intercalation efficaciously increased the specific surface areas, which is beneficial for facilitating electrolyte ions transportation. Given the excellent performance, nitrogen doped intercalation TiO2/TiN/Ti3C2Tx bodes well as a promising pseudocapacitor electrode for energy storage applications.
Highlights
Supercapacitors, bridged the gap between lithium-ion batteries and conventional capacitors, have been considered to be a class of state-of-the-art energy storage devices with characteristics of high power density, long cycle life, and fast charge/discharge properties [1,2]
Pseudocapacitors enable the charge storage by mainly taking advantage of fast redox reactions based on metal oxides, sulfides and conducting polymers [4,5,6,7]
Researchers have focused on the development of redox-active materials with high specific capacitance and good stability for pseudocapacitors
Summary
Supercapacitors, bridged the gap between lithium-ion batteries and conventional capacitors, have been considered to be a class of state-of-the-art energy storage devices with characteristics of high power density, long cycle life, and fast charge/discharge properties [1,2]. EDLCs commonly exhibit excellent cyclic stability due to the high electrical conductivity and extraordinary chemical stability, while withstanding relatively low specific capacitance because of the limitation of charge accumulation in electrical double layers [3]. Two-dimensional (2D) materials, like graphene-based composites, have been used in redox capacitors and have shown impressive pseudocapacitance on account of their large electrochemically active surfaces [9]. These pseudocapacitive materials display serious volume changes during the fast charge/discharge processes, resulting in deterioration in cyclability, which curtails their wide scale use [10,11]. Researchers have focused on the development of redox-active materials with high specific capacitance and good stability for pseudocapacitors
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