Rational Design of Transition Metal Phosphates-Metal Nitrides Basedbifunctional Electrocatalysts for Efficient Alkaline Water Splitting

( Thangjam Ibomcha Singh ),이승현 한국공업화학회 2022 한국공업화학회 연구논문 초록집 Vol.2022 No.-

Embedded PEDOT:PSS/AgNFs network flexible transparent electrode for solid-state supercapacitor

Singh, Soram Bobby,Kshetri, Tolendra,Singh, Thangjam Ibomcha,Kim, Nam Hoon,Lee, Joong Hee Elsevier 2019 Chemical engineering journal Vol.359 No.-

<P><B>Abstract</B></P> <P>Energy storage devices that offer high energy storage capacity along with high electro-optical and mechanical performance is still a great challenge as a power source for transparent electronic gadgets. Here, we report the fabrication of an ultra-flexible, lightweight embedded PEDOT:PSS/AgNFs/NOA 63 hybrid transparent supercapacitor electrode (HTSE) film by using a peel-off transfer process technique. The HTSE film shows a good electro-optical performance, the sheet resistance of Rs ∼2.12 Ω/sq at 84.65% transmittance, along with excellent mechanical bending and flexibility characteristics. The HTSE film shows a negligible change in resistance, only a ∼1% increase in resistance is observed after 10,000 bending cycles at a bending radius of 2.0 mm. The HTSE film also exhibits good electrochemical performance with an areal capacitance of 3.64 mF/cm<SUP>2</SUP> at 84.65% transmittance. The fabricated supercapacitor device also exhibits excellent mechanical flexibility, only <1.5% decrease in areal capacitance after 5000 repeated bending cycles at 2.0 mm bending radius. Owing to the high electro-optical, electrochemical and mechanical properties of the HTSE film, the fabricated solid-state supercapacitor device shows high transparency, good electrochemical performance, and long cyclic stability. The HTSE film will be a potential electrode for future transparent portable energy power source, and other flexible transparent electronic devices, an alternative to ITO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultra-flexible PEDOT:PSS/AgNFs/NOA63 network was fabricated by the peel-off transfer process. </LI> <LI> High electro-optical performance with R<SUB>st</SUB> of ∼2.12 Ω/sq at 84.7% transmittance was obtained. </LI> <LI> The supercapacitor exhibits high areal capacitance (0.91 mF/cm<SUP>2</SUP>) with high bending stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Remarkable Bifunctional Oxygen and Hydrogen Evolution Electrocatalytic Activities with Trace-Level Fe Doping in Ni- and Co-Layered Double Hydroxides for Overall Water-Splitting

Rajeshkhanna, G.,Singh, Thangjam Ibomcha,Kim, Nam Hoon,Lee, Joong Hee American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.49

<P>Large-scale H<SUB>2</SUB> production from water by electrochemical water-splitting is mainly limited by the sluggish kinetics of the nonprecious-based anode catalysts for oxygen evolution reaction (OER). Here, we report layer-by-layer in situ growth of low-level Fe-doped Ni-layered double hydroxide (Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH) and Co-layered double hydroxide (Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH), respectively, with three-dimensional microflower and one-dimensional nanopaddy-like morphologies on Ni foam, by a one-step eco-friendly hydrothermal route. In this work, an interesting finding is that both Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH and Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH materials are very active and efficient for OER as well as hydrogen evolution reaction (HER) catalytic activities in alkaline medium. The electrochemical studies demonstrate that Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH material exhibits very low OER and HER overpotentials of 249 and 273 mV, respectively, at a high current density of 50 mA cm<SUP>-2</SUP>, whereas Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH exhibits 297 and 319 mV. To study the overall water-splitting performance using these electrocatalysts as anode and cathode, three types of alkaline electrolyzers are fabricated, namely, Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(+)∥Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(−), Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(+)∥Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(−), and Co<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(+)∥Ni<SUB>1-<I>x</I></SUB>Fe<I><SUB>x</SUB></I>-LDH(−). These electrolyzers require only a cell potential (<I>E</I><SUB>cell</SUB>) of 1.60, 1.60, and 1.59 V, respectively, to drive the benchmark current density of 10 mA cm<SUP>-2</SUP>. Another interesting finding is that their catalytic activities are enhanced after stability tests. Systematic analyses are carried out on both electrodes after all electrocatalytic activity studies. The developed three types of electrolyzers to produce H<SUB>2</SUB>, are very efficient, cost-effective, and offer no complications in synthesis of materials and fabrication of electrolyzers, which can greatly enable the realization of clean renewable energy infrastructure.</P> [FIG OMISSION]</BR>

Effect of reducing agents on the synthesis of anisotropic gold nanoparticles

Yoo Sunghoon,남동환,Singh Thangjam Ibomcha,Leem Gyu,이승현 나노기술연구협의회 2022 Nano Convergence Vol.9 No.5

The seed-mediated method is a general procedure for the synthesis of gold nanorods (Au NRs), and reducing agents such as ascorbic acid (AA) and hydroquinone (HQ) are widely used for the growth process. Further, they are mild reducing agents; however, when AA is used, controlling the size of Au NRs with a higher aspect ratio (localized surface plasmon resonance (LSPR) peak, λ Lmax > 900 nm) is challenging because it results in a faster growth rate of Au NRs. In contrast, when HQ is used, Au NRs with a higher aspect ratio can be synthesized as it slows down the growth rate of the Au NRs and greatly enhanced the λ Lmax . However, the increase in λ Lmax is still needs not satisfactory due to the limited enhancement in the aspect ratio of Au NRs due to utilization of single reducing agent. The growth kinetics of the Au NRs can be modulated by controlling the reducing power of the reducing agents. In such scenario, judicious use of two reducing agents such as AA and HQ simultaneously can help us to design Au NRs of higher aspect ratio in a controlled manner due to the optimum growth rate resulting from the combined effect of both the reducing agents. In this study, we investigated the effect of the two reducing agents by controlling the volume ratios. When the growth solution contains both the reducing agents, the growth of Au NRs is first initiated by the fast reduction of ­Au 3+ to ­Au + due to stronger reducing power of the AA and when the AA in the growth solution is completely utilized, further growth of the Au NRs continues as a result of the HQ thereby resulting to high aspect ratio Au NRs. Consequently, the LSPR peak (λ Lmax > 1275 nm) can be tuned by controlling the volume ratios of the reducing agents.

Mesoporous iron sulfide nanoparticles anchored graphene sheet as an efficient and durable catalyst for oxygen reduction reaction

Gautam, Jagadis,Tran, Duy Thanh,Singh, Thangjam Ibomcha,Kim, Nam Hoon,Lee, Joong Hee Elsevier 2019 Journal of Power Sources Vol.427 No.-

<P><B>Abstract</B></P> <P>The fabrication of low-cost, highly efficient, and earth-abundant electrocatalysts for oxygen reduction reaction is critical to produce clean and sustainable fuel through an electrochemical process. Herein, a facile hydrothermal technique is used for the synthesis of iron sulfide/graphene hybrid for oxygen reduction reaction. Morphological analysis of the resulting catalyst reveals that iron sulfide nanoparticles are homogeneously embedded on the surface of reduced graphene oxide sheet. Electrochemical analysis of the hybrid exhibits remarkably improved catalytic performance for oxygen reduction reaction while achieving half wave potential of +0.845 V and onset potential of +1.0 V (<I>versus</I> reversible hydrogen electrode), along with outstanding long-term stability under alkaline conditions. In addition, the methanol tolerance ability and stability of the hybrid exceed the benchmark platinum/carbon product in alkaline condition. These outstanding activities of the hybrid are attributed to the merits of the interaction between iron sulfide nanoparticles and graphene. The results suggest the practicability of metal sulfide as a low cost and efficient alternative catalyst of platinum for oxygen reduction reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrothermal technique is used for fabricating a new iron sulfide/graphene hybrid. </LI> <LI> The interaction of mesoporous iron sulfide and graphene produces excellent activity. </LI> <LI> The hybrid outperforms Pt/C and other metal sulfide/graphene catalysts towards ORR. </LI> <LI> The hybrid's stability and methanol tolerance are superior to Pt/C product. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>