Amr Sabbah, Indrajit Shown*, Mohammad Qorbani, Fang-Yu Fu, Tsai-Yu Lin, Heng-Liang Wu, Po-Wen Chung, Chih-I. Wu, Svette Reina Merden Santiago, Ji-Lin Shen, Kuei-Hsien Chen*, Li-Chyong Chen*
Nano Energy, 93, 106809 (2022).
Employing direct Z-scheme semiconductor heterostructures in photocatalysis offers efficient charge carrier separation and isolation of both redox reactions, thus beneficial to reduce CO2 into solar fuels. Here, a ZnS/ZnIn2S4 heterostructure, comprising cubic ZnS nanocrystals on hexagonal ZnIn2S4 (ZIS) nanosheets, is successfully fabricated in a single-pot hydrothermal approach. The composite ZnS/ZnIn2S4 exhibits microstrain at its interface with an electric field favorable for Z-scheme. At an optimum ratio of Zn:In (~ 1:0.5), an excellent photochemical quantum efficiency of around 0.8% is reached, nearly 200-fold boost compared with pristine ZnS. Electronic levels and band alignments are deduced from ultraviolet photoemission spectroscopy and UV-Vis. Evidence of the direct Z-scheme and carrier dynamics is verified by photo-reduction experiment, along with photoluminescence (PL) and time-resolved PL. Finally, diffuse-reflectance infrared Fourier transformed spectroscopy explores the CO2 and related intermediate species adsorbed on the catalyst during the photocatalytic reaction. This microstrain-induced direct Z-scheme approach opens a new pathway for developing next-generation photocatalysts for CO2 reduction.
Hsiang-Ting Lien, Sun-Tang Chang, Po-Tuan Chen, Deniz P. Wong, Yu-Chung Chang, Ying-Rei Lu, Chung-Li Dong, Chen-Hao Wang, Kuei-Hsien Chen & Li-Chyong Chen
Nature Commmunictions 11, 4233 (2020).
Nonnoble metal catalysts are low-cost alternatives to Pt for the oxygen reduction reactions (ORRs), which have been studied for various applications in electrocatalytic systems. Among them, transition metal complexes, characterized by a redox-active single-metal-atom with biomimetic ligands, such as pyrolyzed cobalt–nitrogen–carbon (Co–N x /C), have attracted considerable attention. Therefore, we reported the ORR mechanism of pyrolyzed Vitamin B12 using operando X-ray absorption spectroscopy coupled with electrochemical impedance spectroscopy, which enables operando monitoring of the oxygen binding site on the metal center. material design strategies for high-performance electrocatalysts for fuel cell applications. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, provide insight into metal active-site geometry and structural evolution during ORR, which could be used for developing material design strategies for high performance electrocatalysts for fuel cell applications.
Ming-Chiang Chang, Po-Hsun Ho, Mao-Feng Tseng, Fang-Yuan Lin, Cheng-Hung Hou, I-Kuan Lin, Hsin Wang, Pin-Pin Huang, Chun-Hao Chiang, Yueh-Chiang Yang, I-Ta Wang, He-Yun Du, Cheng-Yen Wen, Jing-Jong Shyue, Chun-Wei Chen, Kuei-Hsien Chen, Po-Wen Chiu & Li-Chyong Chen
Nature Commmunictions 11, 3682 (2020).
In this study, a self-capping vaporliquid-solid reaction is proposed to fabricate large-grain, continuous MoS2 films. An intermediate liquid phase-Na2Mo2O7 is formed through a eutectic reaction of MoO3 and NaF,followed by being sulfurized into MoS2. The as-formed MoS2 seeds function as a capping layer that reduces the nucleation density and promotes lateral growth. By tuning the driving force of the reaction, large mono/bilayer (1.1 mm/200 μm) flakes or full-coverage films (with a record-high average grain size of 450 μm) can be grown on centimeter-scale substrates. The field-effect transistors fabricated from the full-coverage films show high mobility (33 and 49 cm2V-1s-1 for the mono and bilayer regions) and on/off ratio (1 ~ 5 × 108) across a 1.5 cm × 1.5 cm region.
Abhishek Pathak, Jing-Wen Shen, Muhammad Usman, Ling-Fang Wei, Shruti Mendiratta, Yu-Shin Chang, Batjargal Sainbileg, Chin-May Ngue, Ruei-San Chen, Michitoshi Hayashi, Tzuoo-Tsair Luo, Fu-Rong Chen, Kuei-Hsien Chen,* Tien-Wen Tseng,* Li-Chyong Chen,* Kuang-Lieh Lu*
Nature Communications 10, Article number: 1721 (2019).
A new strategy for integrating a metal–sulfur plane within a MOF to achieve high electrical conductivity is reported. This successful design is significant for its potential applications in diverse areas encompassing energy storage and generation. Single crystals of a copper-based metal–organic framework consisting of 2D (–Cu–S–)n plane were synthesized by combining Cu(NO3)2 and 6,6ʹ-dithiodinicotinic acid via the in-situ cleavage of an S–S bond under hydrothermal conditions. This copper-based MOF was found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm−1) among MOFs for single crystal measurements. This study carried out by Kuang-Lieh Lu, Kuei-Hsien Chen, Li-Chyong Chen, Tien-Wen Tseng along with Michitoshi Hayashi, Ruei-San Chen, Fu-Rong Chen and their students provides an excellent example of interdisciplinary collaboration efforts. In addition, these results provide distinctive applications of highly conductive MOF in batteries, thermoelectric, supercapacitors and related areas.
NATURE COMMUNICATIONS (DOI: 10.1038/s41467-017-02547-4, 2018)
Carbon-doped SnS2 (SnS2-C) metal dichalcogenide nanostructure has been synthesized using a hydrothermal technique, which exhibits a highly active and selective photocatalytic conversion of CO2 to hydrocarbons under visible-light, attaining a photochemical quantum efficiency of above 0.7%. The SnS2 -C photocatalyst represents an important contribution towards high quantum efficiency artificial photosynthesis based on gas phase photocatalytic CO2 reduction under visible light.
I. Shown, H.C. Hsu, Y.C. Chang, C.H. Lin, P.K. Roy, A. Ganguly, C.H. Wang, J.K. Chang, C.I. Wu, L.C. Chen, K.H. Chen
Nano Letters, 14(11), 6097-6103 (2014)
In this study, copper nanoparticles (Cu-NPs) decorated graphene oxide (Cu/GO) has been used to enhance photocatalytic CO2 reduction under visible-light. A rapid one-pot microwave process was used to prepare the Cu/GO hybrids with various Cu contents. The attributes of metallic copper nanoparticles (~4-5 nm) in GO hybrid predominately enhance the photocatalytic activity of GO, which is primarily due to the suppression of electron-hole pair recombination, further reduction of GO's bandgap, and modification of their work function. X-ray photoemission spectroscopy studies indicate a charge transfer from GO to Cu. Strong metal-support interaction is also proposed to play some role in the selection of reactions and products. More than 60 times enhancement in CO2 to fuel catalytic efficiency has been demonstrated using Cu/GO-2 (10 wt% Cu) comparative to that using pristine GO; or 240 times enhancement comparative to P25.