Hierarchically structured photoanode with enhanced charge collection and light harvesting abilities for fiber-shaped dye-sensitized solar cells

Liu, Guicheng,Wang, Manxiang,Wang, Hui,Ardhi, Ryanda Enggar Anugrah,Yu, Hyunjin,Zou, Dechun,Lee, Joong Kee Elsevier 2018 Nano energy Vol.49 No.-

<P><B>Abstract</B></P> <P>The performances of fiber dye-sensitized solar cells (FDSSCs), in terms of charge collection efficiency, light-harvesting ability, and structural stability, are improved through a novel hierarchically structured photoanode based on a Ti microridge/nanorod-modified wire substrate. The microridge made of several Ti micropits is inserted into TiO<SUB>2</SUB> layer to shorten the photoelectron transport distance from the original place in the TiO<SUB>2</SUB> layer to substrate and to increase the electron transport rate. The Ti micropits are used as light-gathering centers to collect the reflected light. Meanwhile, the Ti nanorods are evenly distributed on the surface of the microridge-coated Ti wire substrate, which increases the contact area between the substrate and the TiO<SUB>2</SUB> layer in order to suppress the electron recombination and scatters the incident light to further improve the light-harvesting ability. Therefore, the charge collection and power conversion efficiencies of the novel FDSSC have been accordingly enhanced by 17.7% and 61.6%, respectively, compared with traditional FDSSC. Moreover, the structural stability of the novel FDSSC has been strengthened.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchically structured photoanode substrate is a Ti microridge/nanorod-modified wire. </LI> <LI> Novel design enhances charge collection and light-harvesting abilities, concurrently. </LI> <LI> Novel FDSSC exhibits the highest PCE of 8.128% in the field of nanocrystalline-based FDSSCs so far. </LI> <LI> Ti microridges shorten photoelectron transport distance and are used as light-gathering centers. </LI> <LI> Ti nanorods suppress electron recombination and scatters the incident light. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The performances such as charge collection efficiency, light-harvesting ability and structural stability of fiber dye-sensitized solar cells (FDSSCs) are improved through a novel hierarchically structured photoanode based on a Ti microridge/nanorod-modified wire-substrate.</P> <P>[DISPLAY OMISSION]</P>

Design of 3-electrode system for <i>in situ</i> monitoring direct methanol fuel cells during long-time running test at high temperature

Liu, Guicheng,Li, Xinyang,Wang, Hui,Liu, Xiuying,Chen, Ming,Woo, Jae Young,Kim, Ji Young,Wang, Xindong,Lee, Joong Kee Elsevier 2017 APPLIED ENERGY Vol.197 No.-

<P>To understand the effect mechanisms of long-time running and high operation temperature on performance of the direct methanol fuel cell (DMFC) more clearly and directly, in this paper, a new design of 3-electrode system with a solution-type salt bridge has been developed to distinguish the integral polarization into anodic and cathodic polarizations at various temperatures and explore the attenuation mechanism by in situ monitoring the potential of anode during long-time running process at 80 degrees C, for the first time. The results indicate that the optimized 3-electrode system consists of a standard calomel electrode (SCE) and a solution-type salt bridge placed in the anode hole filled by 0.5 mol L-1 H2SO4 solution. By utilization of the 3-electrode system, the effect mechanisms of the running temperature and time on electrochemical parameters of the DMFC have been found: (1) The increasing operation temperature improves cathodic performance more significantly than that of anode; (2) the attenuation of fuel cell performance mainly comes from that of anode during the 20-h running test at 80 degrees C, resulting from the sharp drop of electrochemical active surface area of anode. More important, the new 3-electrode system has simplified the detection equipment and reduced the operating difficulty in a practical application for DMFCs, resulting in its portability. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Soft, Highly Elastic, and Discharge-Current-Controllable Eutectic Gallium-Indium Liquid Metal-Air Battery Operated at Room Temperature

Liu, Guicheng,Kim, Ji Young,Wang, Manxiang,Woo, Jae-Young,Wang, Lei,Zou, Dechun,Lee, Joong Kee Wiley (John WileySons) 2018 Advanced energy materials Vol.8 No.16

Study on a stretchable, fiber-shaped, and TiO₂ nanowire array-based dye-sensitized solar cell with electrochemical impedance spectroscopy method

Liu, Guicheng,Wang, Hui,Wang, Manxiang,Liu, Wenbing,Anugrah Ardhi, Ryanda Enggar,Zou, Dechun,Lee, Joong Kee Elsevier 2018 ELECTROCHIMICA ACTA Vol.267 No.-

<P><B>Abstract</B></P> <P>A spring-like Ti@TiO<SUB>2</SUB> nanowire array wire has been introduced into a stretchable fiber-shaped dye-sensitized solar cell (FDSSC) as a photoanode to achieve high flexibility and elasticity in this paper. Given the TiO<SUB>2</SUB> layer, which was prepared by a hydrothermal reaction in the optimized NaOH concentration of 2.5 mol L<SUP>−1</SUP>, with a 1D structure and high adhesion between the TiO<SUB>2</SUB> nanowire array and the Ti wire substrate, the novel FDSSC still possesses photoelectric conversion efficiency retention rates of approximately 97.00% and 95.95% after bending to a radius of 1.0 cm and stretching to 100% strain, respectively. EIS result shows the degradation mechanism of the FDSSC photoelectric performance: the bending test leads to more terrible electron combination; the stretching operation increases the internal resistance and charge-transfer resistance at the counter electrode. Moreover, it's worth noting that, this is the first time to show a 100%-stretching degree in the FDSSC research field so far.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A fiber-shaped, stretchable, TiO<SUB>2</SUB> nanowire array-based DSSC was reported firstly. </LI> <LI> Using EIS analysis method to analyse effect of bending and stretching on FDSSC performance. </LI> <LI> Photoelectric conversion efficiency retention rate of 95.95% after stretching to 100% strain. </LI> <LI> High flexibility with 97.00% performance retention rate at bending radius of 1 cm. </LI> </UL> </P>

Pseudocapacitive Characteristics of Low-Carbon Silicon Oxycarbide for Lithium-Ion Capacitors

Halim, Martin,Liu, Guicheng,Ardhi, Ryanda Enggar Anugrah,Hudaya, Chairul,Wijaya, Ongky,Lee, Sang-Hyup,Kim, A-Young,Lee, Joong Kee American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.24

<P>Lithium-ion capacitors (LICs) and lithium-ion batteries (LIBs) are important energy storage devices. As a material with good mechanical, thermal, and chemical properties, low-carbon silicon oxycarbide (LC-SiOC), a kind of silicone oil-derived SiOC, is of interest as an anode material, and we have examined the electrochemical behavior of LC-SiOC in LIB and LIC devices. We found that the lithium storage mechanism in LC-SiOC, prepared by pyrolysis of phenyl-rich silicon oil, depends on an oxygen-driven rather than a carbon-driven mechanism within our experimental scope. An investigation of the electrochemical performance of LC-SiOC in half- and full-cell LIBs revealed that LC-SiOC might not be suitable for full-cell LIBs because it has a lower capacity (238 mAh g(-1)) than that of graphite (290 mAh g(-1)) in a cutoff voltage range of 0-1 V versus Li/Li+, as well as a substantial irreversible capacity. Surprisingly, LC-SiOC acts as a pseudocapacitive material when it is tested in a half-cell configuration within a narrow cutoff voltage range of 0-1 V versus Li/Li+. Further investigation of a 'hybrid' supercapacitor, also known as an LIC, in which LC-SiOC is coupled with an activated carbon electrode, demonstrated that a power density of 156 000 W kg(-1) could be achieved while maintaining an energy density of 25 Wh kg(-1). In addition, the resulting capacitor had an excellent cycle life, holding similar to 90% of its energy density even after 75 000 cycles. Thus, LC-SiOC is a promising active material for LICs in applications such as heavy-duty electric vehicles.</P>

ZnO Nanorod Array Modified PVDF Membrane with Superhydrophobic Surface for Vacuum Membrane Distillation Application

Wang, Manxiang,Liu, Guicheng,Yu, Hyunjin,Lee, Sang-Hyup,Wang, Lei,Zheng, Jianzhong,Wang, Tao,Yun, Yanbin,Lee, Joong Kee American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.16

<P>The vacuum membrane distillation (VMD) is a promising technology for lots of applications. To solve the membrane fouling and wetting problems, in this paper, a novel ZnO nanorods 1<I>H</I>,1<I>H</I>,2<I>H</I>,2<I>H</I>-perfluorodecyltriethoxysilane (PDTS) modified poly(vinylidene fluoride) (PVDF) membrane with a micro/nanoscale hierarchical structure and a superhydrophobic surface has been prepared and applied to the VMD process for distilling highly salty water, for the first time. Among these, a pyrolysis-adhesion method is created to obtain the ZnO seeds and fasten them on the PVDF substrate firmly. The novel modified membrane shows a stable superhydrophobic surface with a water contact angle of 152°, easy cleaning property, excellent thermal and mechanical stability, because of the Cassie’s state caused by pocketing much air in the hydrophobized ZnO nanorods, the low surface energy of PDTS coating, and the strong adhesion between ZnO nanorods and PVDF membrane, which has built an ideal structure for VMD application. After 8 h VMD of 200 g L<SUP>-1</SUP> NaCl solution, compared to the virgin PVDF membrane, the novel membrane shows a similar permeate flux but a much higher quality permeated liquid because of its unique antifouling and antiwetting caused by the several microns gap between the feed and the membrane. Due to its easy cleaning property, the novel membrane also exhibits an excellent reusability.</P> [FIG OMISSION]</BR>

Microstructure-modified proton exchange membranes for high-performance direct methanol fuel cells

Wang, Manxiang,Liu, Guicheng,Tian, Zhe,Shao, Yingna,Wang, Lei,Ye, Feng,Tran, Minh Xuan,Yun, Yanbin,Lee, Joong Kee Elsevier 2017 Energy conversion and management Vol.148 No.-

<P><B>Abstract</B></P> <P>To lower methanol crossover and volume swelling degree, and to improve proton conductivity, a simple hot-mould-modifying method has been introduced to modify Nafion membrane for the direct methanol fuel cell application. To evaluate effect of the modification on properties of the Nafion membrane and fuel cell performance, a series of measurements of membranes and fuel cells have been carried out. The results show that, compared with the normal membrane, the modified Nafion membrane with regular spindle-type groove array possesses higher proton conductivity and methanol diffusion resistance, and 31.9% better dimensional stability, owing to its larger electrical double-layer capacitance come from the higher contact area between electron-electrode and ion electrolyte, and its more compact internal structure. And also, the direct methanol fuel cell based on the modified Nafion membrane shows 13.3% higher discharge power density and better long-time running performance than the normal one. Furthermore, this hot-mould-modifying method could be introduced into doping/coating-modified membranes reported in the current literature to further modify Nafion membranes, because this method is compatible with the current modifications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simple hot-mould-modified Nafion membrane is used for direct methanol fuel cells. </LI> <LI> Regular spindle-type groove array is uniformly distributed on the membrane surface. </LI> <LI> Modification lowers methanol crossover, swelling, and improves proton conductivity. </LI> <LI> Power density and long-time running performance of fuel cells are improved visibly. </LI> <LI> This method provides a practicable way for direct methanol fuel cell applications. </LI> </UL> </P>

Effect of pulse electrodeposition parameters on electrocatalytic the activity of methanol oxidation and morphology of Pt/C catalyst for direct methanol fuel cells

Ye, Feng,Xu, Chao,Liu, Guicheng,Yuan, Mengdi,Wang, Zhiming,Du, Xiaoze,Lee, Joong Kee Pergamon 2018 Energy Conversion and Management Vol. No.

<P><B>Abstract</B></P> <P>The electrodeposition technique for preparing direct methanol fuel cell electrodes has been developed to increase the Pt utilization and lower the Pt loading. The performance of the Pt/C electrode for methanol oxidation reaction (MOR) was optimized by adjusting the electrodeposition parameters such as applied electrical signal types, ratios of t<SUB>on</SUB>/t<SUB>off</SUB>, deposition temperatures, and electrolyte concentrations, systematically. Furthermore, the effects of two kinds of additives, i.e. polyethylene glycol (PEG) and sodium dodecyl sulfonate (SDS), on the catalytic performance and morphology of Pt catalyst were investigated for MOR by SEM, XRD, cyclic voltammetry and linear sweep voltammetry. The results show that the optimal Pt catalyst has been prepared by the square wave current method with t<SUB>on</SUB>/t<SUB>off</SUB> of 1 s/5 s at 30 °C in a 1.0 mmol L<SUP>−1</SUP> H<SUB>2</SUB>PtCl<SUB>6</SUB> solution with a 10<SUP>−4</SUP> mmol L<SUP>−1</SUP> PEG additive. Moreover, the effect of the additive type and amount on the formation mechanism of the Pt crystallite morphology has also been discussed. From the results, introducing additives into the deposition solution in the pulse electrodeposition process is useful for designing and fabricating electrocatalytic electrodes for direct methanol fuel cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Signals include square wave current and potential, cyclic voltammetry and constant current pulse. </LI> <LI> Effects of four applied electrical signal types on Pt catalytic performance are compared. </LI> <LI> Parameters for Pt electrodeposition in constant current pulse mode are optimized systematically. </LI> <LI> Effect mechanism of additive on growth of Pt catalyst is studied in pulse electrodeposition. </LI> <LI> Optimal condition is t<SUB>on</SUB>/t<SUB>off</SUB> of 1 s/5 s, 30 °C, 1 mmol L<SUP>−1</SUP> H<SUB>2</SUB>PtCl<SUB>6</SUB> solution with 10<SUP>−4</SUP> mmol L<SUP>−1</SUP> PEG. </LI> </UL> </P>

Self-Relaxant Superelastic Matrix Derived from C₆₀ Incorporated Sn Nanoparticles for Ultra-High-Performance Li-Ion Batteries

Ardhi, Ryanda Enggar Anugrah,Liu, Guicheng,Tran, Minh Xuan,Hudaya, Chairul,Kim, Ji Young,Yu, Hyunjin,Lee, Joong Kee American Chemical Society 2018 ACS NANO Vol.12 No.6

<P>Homogeneously dispersed Sn nanoparticles approximately ⩽10 nm in a polymerized C<SUB>60</SUB> (PC<SUB>60</SUB>) matrix, employed as the anode of a Li-ion battery, are prepared using plasma-assisted thermal evaporation coupled by chemical vapor deposition. The self-relaxant superelastic characteristics of the PC<SUB>60</SUB> possess the ability to absorb the stress-strain generated by the Sn nanoparticles and can thus alleviate the problem of their extreme volume changes. Meanwhile, well-dispersed dot-like Sn nanoparticles, which are surrounded by a thin SnO<SUB>2</SUB> layer, have suitable interparticle spacing and multilayer structures for alleviating the aggregation of Sn nanoparticles during repeated cycles. The Ohmic characteristic and the built-in electric field formed in the interparticle junction play important roles in enhancing the diffusion and transport rate of Li ions. SPC-50, a Sn-PC<SUB>60</SUB> anode consisting of 50 wt % Sn and 50 wt % PC<SUB>60</SUB>, as confirmed by energy-dispersive X-ray spectroscopy analysis, exhibited the highest electrochemical performance. The resulting SPC-50 anode, in a half-cell configuration, exhibited an excellent capacity retention of 97.18%, even after 5000 cycles at a current density of 1000 mA g<SUP>-1</SUP> with a discharge capacity of 834.25 mAh g<SUP>-1</SUP>. In addition, the rate-capability performance of this SPC-50 half-cell exhibited a discharge capacity of 544.33 mAh g<SUP>-1</SUP> at a high current density of 10 000 mA g<SUP>-1</SUP>, even after the current density was increased 100-fold. Moreover, a very high discharge capacity of 1040.09 mAh g<SUP>-1</SUP> was achieved with a capacity retention of 98.67% after 50 cycles at a current density of 100 mA g<SUP>-1</SUP>. Futhermore, a SPC-50 full-cell containing the LiCoO<SUB>2</SUB> cathode exhibited a discharge capacity of 801.04 mAh g<SUP>-1</SUP> and an areal capacity of 1.57 mAh cm<SUP>-2</SUP> with a capacity retention of 95.27% after 350 cycles at a current density of 1000 mA g<SUP>-1</SUP>.</P> [FIG OMISSION]</BR>

N-isopropyl acrylamide/sodium acrylate hydrogel as draw agent for forward osmosis to concentrate esterification wastewater

Yan Le,Yanbin Yun,왕만상,Wenli Liu,Shuangshuang Dong,Kai Yang,Syed Taj Ud Din,Woochul Yang,Guicheng Liu 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.5

In recent years, a temperature-sensitive hydrogel was reported as a promising draw agent in forward osmosis (FO) technology. PEG, acts as porogen, as an enabler to improve the swelling property of hydrogels. From FO test, the addition of porogen to the hydrogel can improve the water flux of FO by increasing the swelling properties of the hydrogel. And the hydrogel modified with porogen improves the concentration efficiency of wastewater from 1.09 to 1.124 times, indicating that the modification of the hydrogel by the porogen has positive significance for FO technology. In this study, an advanced hydrogel was synthesized via physical copolymerization by using N-isopropylacrylamide and sodium acrylate. The internal structure was investigated by SEM test where it was found that that porogens have different mechanisms of action on hydrogel performance: Porogen affects the swelling property of hydrogel by changing the internal network structure through physical “occupation”. The effect of porogen concentration is to act on the porosity of hydrogel, while the main effect of the molecular weight of porogen on the hydrogel structure is by altering the pore size.