Enhanced charge separation of CuS and CdS quantum-dot-cosensitized porous TiO₂-based photoanodes for photoelectrochemical water splitting

Du, Jimin,Yang, Mengke,Zhang, Fangfang,Cheng, Xuechun,Wu, Haoran,Qin, Huichuang,Jian, Qingsong,Lin, Xialing,Li, Kaidi,Kang, Dae Joon Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.3

<P><B>Abstract</B></P> <P>Photoelectrochemical (PEC) water splitting using high-performance catalysts shows considerable promise in generating environment-friendly hydrogen energy. Its practical applications, however, suffer from several shortcomings, such as low photocurrent density, large onset-voltage value, and poor durability. In this study, CuS and CdS quantum-dot-cosensitized porous TiO<SUB>2</SUB>-based PEC catalysts (CuS-CT) have been successfully synthesized via in situ sulfuration of CuO and CdO coexisting inside a porous TiO<SUB>2</SUB> monolith by a hydrothermal method. Compared to porous TiO<SUB>2</SUB>, CuS-sensitized porous TiO<SUB>2</SUB> (CuS-TiO<SUB>2</SUB>), and CdS-sensitized porous TiO<SUB>2</SUB> (CdS-TiO<SUB>2</SUB>) in terms of PEC performance, the CuS-CT photoanode exhibited a significantly high anodic photocurrent for water splitting under simulated sunlight radiation. The photocurrent produced by the optimized sample of 7% CuS-5% CdS-TiO<SUB>2</SUB> (7% CuS-CT) was nearly 2.7 times higher than that of pure porous TiO<SUB>2</SUB> at 1.0V versus a reversible hydrogen electrode (RHE). Porous TiO<SUB>2</SUB> possesses large surface areas that can drive fast electrolyte transport and afford more surface reaction active sites. On the other hand, CuS and CdS quantum dots not only broaden the visible light absorption range, but also improve photoinduced electron-hole separation efficiency. The co-sensitized multi-nanostructures photoanodes lead to a remarkable and promising application in PEC water splitting reactions.</P>

Highly efficient hydrogen evolution catalysis based on MoS₂/CdS/TiO₂ porous composites

Du, Jimin,Wang, Huiming,Yang, Mengke,Zhang, Fangfang,Wu, Haoran,Cheng, Xuechun,Yuan, Sijie,Zhang, Bing,Li, Kaidi,Wang, Yina,Lee, Hyoyoung Elsevier 2018 International journal of hydrogen energy Vol.43 No.19

<P><B>Abstract</B></P> <P>Efficient production of hydrogen through visible-light-driven water splitting mechanism using semiconductor-based composites has been identified as a promising strategy for converting light into clean H<SUB>2</SUB> fuel. However, researchers are facing lots of challenges such as light absorption and electron-hole pair recombination and so on. Here, new sheet-shaped MoS<SUB>2</SUB> and pyramid-shaped CdS <I>in-situ</I> co-grown on porous TiO<SUB>2</SUB> photocatalysts (MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB>) are successfully obtained <I>via</I> mild sulfuration of MoO<SUB>3</SUB> and CdO coexisted inside porous TiO<SUB>2</SUB> monolith by a hydrothermal route. The scanning electron microscopy and transmission electron microscopy results exhibit that the MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB> composites have average pore size about 500 nm. The 3%MoS<SUB>2</SUB> 10%CdSTiO<SUB>2</SUB> demonstrated excellent photocatalytic activity and high stability for a hydrogen production with a high H<SUB>2</SUB>-generation rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> under visible light irradiation even without noble-metal co-catalysts. The super photocatalytic performance of the visible-light-driven hydrogen evolution is predominantly attributed to the synergistic effect. The conduction band of MoS<SUB>2</SUB> facilitates in transporting excited electrons from visible-light on CdS to the porous TiO<SUB>2</SUB> for catalytic hydrogen production, and holes to MoS<SUB>2</SUB> for inhibiting the photocorrosion of CdS, respectively, leading to enhancing the efficient separation of electrons and holes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB>-CT photocatalysts have been successfully synthesized by two-step method. </LI> <LI> The porous structure can enhance photogenerated electron-hole pairs separation. </LI> <LI> The 3% MoS<SUB>2</SUB>-CT shows an excellent H<SUB>2</SUB> evolution rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Porous NiCo2S4 Networks as Electrodes for Electrochemical Supercapacitors

Jimin Du,Kaidi Li,Yongteng Qian,Mengke Yang,Huiming Wang,Wen He,Viyada Harnchana 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12

Porous NiCo2S4 networks have been successfully synthesized by a facile one-pot solvothermal method without the use of any surfactant or template. Crystal structure, morphology, composition and surface area of the as-synthesized samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer– Emmet–Teller techniques. Owing to their porous nature and small crystalline size, the as-prepared NiCo2S4 networks based supercapacitor electrodes showed a high specific capacitance of 1250 F · g-1 at 1 A · g-1, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte.

Pyramid-like CdS nanoparticles grown on porous TiO₂ monolith: An advanced photocatalyst for H₂ production

Du, Jimin,Wang, Huiming,Yang, Mengke,Li, Kaidi,Zhao, Lixin,Zhao, Guoyan,Li, Sujuan,Gu, Xiaolei,Zhou, Yalan,Wang, Le,Gao, Yating,Wang, Weimin,Kang, Dae Joon Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Efficient production of H<SUB>2</SUB> via solar-light-driven water splitting by a semiconductor-based photocatalyst without noble metals is crucial owing to increasingly severe global energy and environmental issues. However, many challenges, including the low efficiency of H<SUB>2</SUB> evolution, low solar light absorption, excited electron–hole pair recombination, and slow transport of photoexcited carriers, must be resolved to enhance the H<SUB>2</SUB> photoproduction efficiency and photocatalyst stability. Here, a two-step method is used to synthesize advanced H<SUB>2</SUB>-generating photocatalysts consisting of pyramid-like CdS nanoparticles grown on a porous TiO<SUB>2</SUB> monolith, which show promising photocatalytic activity for the hydrogen evolution reaction. Furthermore, the stability of the photocatalysts is examined through long-term tests to verify their good durability. Without noble metals as cocatalysts, the photocatalyst can reach a high H<SUB>2</SUB> production rate of 1048.7μmolh<SUP>−1</SUP> g<SUP>−1</SUP> under UV–vis irradiation when the ratio of the CdS nanoparticles to TiO<SUB>2</SUB> is 5mol%. This unusual photocatalytic activity arises from the wide-region light adsorption due to the narrow band gap of CdS, effective separation of electrons and holes due to conduction band alignment at the CdS–TiO<SUB>2</SUB> interface, and favorable reaction sites resulting from the porous structure.</P>

Synthesis and Enhanced Photocatalytic Activity of Black Porous Zr-doped TiO2 Monoliths

Jimin Du,Huiming Wang,Huijuan Chen,Menghe Yang,Xiaoling Lu,Hui Guo,Zhanmin Zhang,Tianwei Shang,Shujue Xu,Wenqi Li,Pianpian Wang,Imran Shakir 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.6

Black Porous Zr-doped TiO2 monoliths were successfully synthesized by a combined route including sol–gel method with polystyrene spheres as template followed by calcination at high temperature in the presence of oxygen. As-synthesized samples were then treated in hydrogen atmosphere at 500℃ for 6 h to obtain black Porous Zr-doped TiO2 monoliths. This as-synthesized black porous Zr-doped TiO2 composite showed relatively narrow bandgap compared to the pure anatase phase of TiO2, which may have its origin from the contributions from the Zr impurity and oxygen vacancies. The photocatalytic activity of the black porous Zr-doped TiO2 monolith was examined by carrying out the dye degradation on Rhodamine B under visible irradiation. Our experimental results indicate that black porous 0.9% Zr-doped TiO2 sample exhibits high photocatalytic activity with the photodecomposition of 95.25% under visible irradiation for 120 min.

Elasticity Modulation of Fibroblast-Derived Matrix for Endothelial Cell Vascular Morphogenesis and Mesenchymal Stem Cell Differentiation

Du, Ping,Suhaeri, Muhammad,Subbiah, Ramesh,Van, Se Young,Park, Jimin,Kim, Sang Heon,Park, Kwideok,Lee, Kangwon Mary Ann Liebert 2016 Tissue engineering. Part A Vol.22 No.5

<P>Biophysical properties of the microenvironment, including matrix elasticity and topography, are known to affect various cell behaviors; however, the specific role of each factor is unclear. In this study, fibroblast-derived matrix (FDM) was used as cell culture substrate and physically modified to investigate the influence of its biophysical property changes on human umbilical vein endothelial cells (HUVECs) and human mesenchymal stem cells (hMSCs) behavior in vitro. These FDMs were physically modified by simply storing them at different temperatures: the one stored at 4 degrees C, maintained its original properties, was considered natural FDM, whereas the ones stored at -20 degrees C or -80 degrees C, exhibited a distinct surface morphology, were considered physically modified FDM. Physical modification induced matrix fiber rearrangement in FDM, forming different microstructures on the surface as characterized by focused ion beam (FIB)-cryoSEM. A significant increase of matrix elasticity was found with physically modified FDMs as determined by atomic force microscopy. HUVEC and hMSC behaviors on these natural and physically modified FDMs were observed and compared with each other and with gelatin-coated coverslips. HUVECs showed a similar adhesion level on these substrates at 3 h, but exhibited different proliferation rates and morphologies at 24 h; HUVECs on natural FDM proliferated relatively slower and assembled to capillary-like structures (CLSs). It is observed that HUVECs assembled to CLSs on natural FDMs are independent on the exogenous growth factors and yet dependent on nonmuscle myosin II activity. This result indicates the important role of matrix mechanical properties in regulating HUVECs vascular morphogenesis. As for hMSCs multilineage differentiation, adipogenesis is improved on natural FDM that with lower matrix elasticity, while osteogenesis is accelerated on physically modified FDMs that with higher matrix elasticity, these results further confirm the crucial role of matrix elasticity on cell fate determination.</P>

Magnesium Corrosion Triggered Spontaneous Generation of H₂O₂ on Oxidized Titanium for Promoting Angiogenesis

Park, Jimin,Du, Ping,Jeon, Jin‐,Kyung,Jang, Gun Hyuk,Hwang, Mintai Peter,Han, Hyung‐,Seop,Park, Kwideok,Lee, Kwan Hyi,Lee, Jee‐,Wook,Jeon, Hojeong,Kim, Yu‐,Chan,Park, Jong Woon WILEY‐VCH Verlag 2015 Angewandte Chemie Vol.127 No.49

<P><B>Abstract</B></P><P>Although the use of reactive oxygen species (ROS) has been extensively studied, current systems employ external stimuli such as light or electrical energy to produce ROS, which limits their practical usage. In this report, biocompatible metals were used to construct a novel electrochemical system that can spontaneously generate H<SUB>2</SUB>O<SUB>2</SUB> without any external light or voltage. The corrosion of Mg transfers electrons to Au‐decorated oxidized Ti in an energetically favorable process, and the spontaneous generation of H<SUB>2</SUB>O<SUB>2</SUB> in an oxygen reduction reaction was revealed to occur at titanium by combined spectroscopic and electrochemical analyses. The controlled release of H<SUB>2</SUB>O<SUB>2</SUB> noticeably enhanced in vitro angiogenesis even in the absence of growth factors. Finally, a new titanium implant prototype was developed by Mg incorporation, and its potential for promoting angiogenesis was demonstrated.</P>

Enhanced electrochemical performance of porous Co-doped TiO₂ nanomaterials prepared by a solvothermal method

Qian, Yongteng,Du, Jimin,Kang, Dae Joon Elsevier 2019 Microporous and mesoporous materials Vol.273 No.-

<P><B>Abstract</B></P> <P>Highly porous nanostructures having large specific surface areas are very desirable for electrochemical supercapacitors to achieve a large energy storage capacity. We synthesized porous Co-doped TiO<SUB>2</SUB> nanostructures with an average diameter of 450 nm through a simple solvothermal method by using tetrabutyl titanate and cobalt acetate as precursors and polystyrene beads as templates. The optimized 7% Co-doped TiO<SUB>2</SUB> nanostructures-based supercapacitor electrodes exhibited a specific capacitance of 352 F g<SUP>-1</SUP> at a current density of 0.5 A g<SUP>−1</SUP> while retaining a capacity of 97.2% after 3000 cycles. This excellent electrochemical performance may be ascribed to the synergistic effects originating from conductivity enhancement of TiO<SUB>2</SUB> through optimized Co-doping and larger specific surface areas rendered by structural porosity, when compared to the undoped TiO<SUB>2</SUB> samples. Our results suggest that porous Co-doped TiO<SUB>2</SUB> nanostructures can be explored for potential electrochemical applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of porous Co-doped TiO<SUB>2</SUB> nanostructures by a simple sol–gel method. </LI> <LI> Conductivity enhancement of TiO<SUB>2</SUB> through optimized Co-doping. </LI> <LI> More charge transfer pathways and reaction active sites owing to porosity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis of V₂O₅/RuO₂ Nanocomposites Suitable for a Positive Electrode in Lithium-ion Secondary Batteries

Miwon Kang,Jimin Du,Kyu-Sung Park,Dae Joon Kang 한국표면공학회 2008 한국표면공학회 학술발표회 초록집 Vol.2008 No.-

Controlled synthesis of nanoplate, nanoprism and nanopyramid-shaped CdSe decorated on porous TiO₂ photocatalysts for visible-light-driven hydrogen evolution

Yang, Mengke,Qian, Yongteng,Du, Jimin,Yuan, Sijie,Wang, Sijia,Zhu, Xinrui,Lin, Xialing,Li, Kaidi,Li, Sujuan,Kang, Dae Joon Elsevier 2018 Ceramics international Vol.44 No.11

<P><B>Abstract</B></P> <P>Herein, we report a successful synthesis of porous TiO<SUB>2</SUB> monoliths decorated with unique nanoplate, nanoprism, and nanopyramid-shaped CdSe particles through a mild selenylation of CdO embedded inside porous TiO<SUB>2</SUB> monoliths via a hydrothermal method in a very controlled manner. Compared with pure TiO<SUB>2</SUB>, as-synthesized CdSe/TiO<SUB>2</SUB> photocatalyst not only enhances light absorption but also leads to a highly efficient charge-carrier separation. Particularly, the nanoplate-shaped 7% CdSe/TiO<SUB>2</SUB> photocatalyst (molar percentages of CdSe to TiO<SUB>2</SUB> is 7:100) exhibits an exceptional hydrogen evolution rate up to 3650 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> without resorting to any noble-metal co-catalysts under visible-light irradiation owing to synergistic effects envisaged by a rational material design. Our results may provide a useful strategy to develop a highly-efficient visible-light-driven hydrogen production system via water splitting.</P>