Browsing by Author "Van-Truong Nguyen"

Now showing 1 - 2 of 2

A new redox phloroglucinol additive incorporated gel polymer electrolyte for flexible symmetrical solid-state supercapacitors
(2019-06-01)
Phuoc-Anh Le
;
Van-Truong Nguyen
;
Yen, Po-Jen
;
Tseng, Tseung-Yuen
;
Wei, Kung-Hwa
We reported a new and environmentally friendly phloroglucinol additive incorporated polyvinyl alcohol-LiClO4 gel polymer electrolyte for flexible symmetrical solid-state supercapacitors. The incorporation of 10 wt% phloroglucinol into PVA-LiClO4 gel polymer electrolytes results in much higher specific capacitance (114 F g(-1)) than that without phloroglucinol (60 F g(-1)), an increase of 90%, because of the redox reaction of phloroglucinol in the system. We used the PVA-LiClO4 with 10 wt% phloroglucinol as a gel polymer electrolyte in combination with nitrogen-doped graphene nanosheet-based electrodes as the anode and cathode to fabricate a symmetrical solid-state supercapacitor. The fabricated supercapacitor involving the phloroglucinol redox additive has an energy density of 2.3 W h kg(-1) at a power density of 150 W kg(-1), which is higher than the one without a redox additive (1.9 W h kg(-1) at a power density of 150 W kg(-1)). Moreover, the supercapacitor involving the redox additive has good stability; its capacitance remains at up to similar to 94% after 5000 charge/discharge cycles.
New Simultaneous Exfoliation and Doping Process for Generating MX2 Nanosheets for Electrocatalytic Hydrogen Evolution Reaction
(2019-04-24)
Van-Truong Nguyen
;
Yang, Tzu-Yi
;
Phuoc Anh Le
;
Yen, Po-Jen
;
Chueh, Yu-Lun
Doping nonmetal atoms into layered transition metal dichalcogenide MX2 structures has emerged as a promising strategy for enhancing their catalytic activities for the hydrogen evolution reaction. In this study, we developed a new and efficient one-step approach that involves simultaneous plasma-induced doping and exfoliating of MX2 bulk into nanosheets-such as MoSe2, WSe2, MoS2, and WS2 nano sheets-within a short time and at a low temperature (ca. 80 degrees C). Specifically, by utilizing active plasma that is generated with an asymmetric electrical field during the electrochemical reaction at the surface of the submerged cathode tip, we are able to achieve doping of nitrogen atoms, from the electrolytes, into the semiconducting 2H-MX2 structures during their exfoliation process from the bulk states, forming N-doped MX2. We selected N-doped MoS2 nanosheets for demonstrating their catalytic hydrogen evolution potential. We modulated the electronic and transport properties of the MoS2 structure with the synergy of nitrogen doping and exfoliating for enhancing their catalytic activity. We found that the nitrogen concentration of 5.2 atom % at N-doped MoS2 nanosheets have an excellent catalytic hydrogen evolution reaction, where a low overpotential of 164 mV at a current density of 10 mA cm(-2) and a small Tafel slope of 71 dec mV(-1)-much lower than those of exfoliated MoS2 nanosheets (207 mV, 82 dec mV(-1)) and bulk MoS2 (602 mV, 198 dec mV(-1))-as well as an extraordinary long-term stability of >25 h in 0.5 M H2SO4 can be achieved.