Hammad Elsayed, M, Abdellah M, Alhakemy AZ, Mekhemer IMA, Aboubakr AEA, Chen B-H, Sabbah A, Lin K-H, Chiu W-S, Lin S-J, Chu C-Y, Lu C-H, Yang S-D, Mohamed MG, Kuo S-W, Hung C-H, Chen L-C, Chen K-H, Chou H-H.
2024.
Overcoming small-bandgap charge recombination in visible and NIR-light-driven hydrogen evolution by engineering the polymer photocatalyst structure, 2024. Nature Communications. 15(1):707.
AbstractDesigning an organic polymer photocatalyst for efficient hydrogen evolution with visible and near-infrared (NIR) light activity is still a major challenge. Unlike the common behavior of gradually increasing the charge recombination while shrinking the bandgap, we present here a series of polymer nanoparticles (Pdots) based on ITIC and BTIC units with different π-linkers between the acceptor-donor-acceptor (A-D-A) repeated moieties of the polymer. These polymers act as an efficient single polymer photocatalyst for H2 evolution under both visible and NIR light, without combining or hybridizing with other materials. Importantly, the difluorothiophene (ThF) π-linker facilitates the charge transfer between acceptors of different repeated moieties (A-D-A-(π-Linker)-A-D-A), leading to the enhancement of charge separation between D and A. As a result, the PITIC-ThF Pdots exhibit superior hydrogen evolution rates of 279 µmol/h and 20.5 µmol/h with visible (>420 nm) and NIR (>780 nm) light irradiation, respectively. Furthermore, PITIC-ThF Pdots exhibit a promising apparent quantum yield (AQY) at 700 nm (4.76%).
Krishnamoorthy, V, Sabhapathy P, Raghunath P, Huang C-Y, Sabbah A, Kamal Hussien M, Syum Z, Muthusamy S, Lin M-C, Wu H-L, Chen R-S, Chen K-H, Chen L-C.
2024.
Synergistic Electronic Interaction of Nitrogen Coordinated Fe-Sn Double-Atom Sites: An Efficient Electrocatalyst for Oxygen Reduction Reaction, 2024. Small Methods. n/a(n/a):2301674.: John Wiley & Sons, Ltd
AbstractAbstract Double-atom site catalysts (DASs) have emerged as a recent trend in the oxygen reduction reaction (ORR), thereby modifying the intermediate adsorption energies and increasing the activity. However, the lack of an efficient dual atom site to improve activity and durability has limited these catalysts from widespread application. Herein, the nitrogen-coordinated iron and tin-based DASs (Fe-Sn-N/C) catalyst are synthesized for ORR. This catalyst has a high activity with ORR half-wave potentials (E1/2) of 0.92 V in alkaline, which is higher than those of the state-of-the-art Pt/C (E1/2 = 0.83 V), Fe-N/C (E1/2 = 0.83 V), and Sn-N/C (E1/2 = 0.77 V). Scanning electron transmission microscopy analysis confirmed the atomically distributed Fe and Sn sites on the N-doped carbon network. X-ray absorption spectroscopy analysis revealed the charge transfer between Fe and Sn. Both experimental and theoretical results indicate that the Sn with Fe-NC (Fe-Sn-N/C) induces charge redistribution, weakening the binding strength of oxygenated intermediates and leading to improved ORR activity. This study provides the synergistic effects of DASs catalysts and addresses the impacts of P-block elements on d-block transition metals in ORR.
Muthusamy, S, Sabhapathy P, Raghunath P, Sabbah A, Chang Y-C, Krishnamoorthy V, Ho T-T, Chiou J-W, Lin M-C, Chen L-C, Chen K-H.
2023.
Mimicking Metalloenzyme Microenvironments in the Transition Metal-Single Atom Catalysts for Electrochemical Hydrogen Peroxide Synthesis in an Acidic Medium, 2023. Small Methods. :2300234.: John Wiley & Sons, Ltd
AbstractAbstract Electrochemical reduction of oxygen into hydrogen peroxide in an acidic medium offers an energy-efficient and green H2O2 synthesis as an alternative to the energy-intensive anthraquinone process. Unfortunately, high overpotential, low production rates, and fierce competition from traditional four-electron reduction limit it. In this study, a metalloenzyme-like active structure is mimicked in carbon-based single-atom electrocatalysts for oxygen reduction to H2O2. Using a carbonization strategy, the primary electronic structure of the metal center with nitrogen and oxygen coordination is modulated, followed by epoxy oxygen functionalities close to the metal active sites. In an acidic medium, CoNOC active structures proceed with greater than 98% H2O2 selectivity (2e?/2H+) rather than CoNC active sites that are selective to H2O (4e?/4H+). Among all MNOC (M = Fe, Co, Mn, and Ni) single-atom electrocatalysts, the CoNOC is the most selective (> 98%) for H2O2 production, with a mass activity of 10 A g?1 at 0.60 V vs. RHE. X-ray absorption spectroscopy is used to identify the formation of unsymmetrical MNOC active structures. Experimental results are also compared to density functional theory calculations, which revealed that the structure-activity relationship of the epoxy-surrounded CoNOC active structure reaches optimum (?G*OOH) binding energies for high selectivity.
Muthusamy, S, Sabbah A, Sabhapathy P, Chang Y-C, Billo T, Syum Z, Chen L-C, Chen K-H.
2023.
Modification of Conductive Carbon with N-Coordinated Fe−Co Dual-Metal Sites for Oxygen Reduction Reaction, 2023. ChemElectroChem. n/a(n/a):e202300272.: John Wiley & Sons, Ltd
AbstractAbstract Earth-abundant commercial conductive carbon materials are ideal electrocatalyst supports but cannot be directly utilized for single-atom catalysts owing to the lack of anchoring sites. Therefore, we employed crosslink polymerization to modify the conductive carbon surface with Fe?Co dual-site electrocatalysts for oxygen reduction reaction (ORR). First, metal-coordinated polyurea (PU) aerogels were prepared using via crosslinked polymerization at ambient temperature. Then, carbon-supported, atomically dispersed Fe?Co dual-atom sites (FeCoNC/BP) were formed by high-temperatures pyrolysis with a nitrogen source. FTIR and 13C NMR measurements showed PU linkages, while 15N NMR revealed metal?nitrogen coordination in the PU gels. Asymmetric, N-coordinated, and isolated Fe?Co active structures were found after pyrolysis using XAS and STEM. In alkaline media, FeCoNC/BP exhibited excellent ORR activity, with a E1/2 of 0.93?V vs. RHE, higher than that of Pt/C (20?%) (0.90?V), FeNC/BP (0.88?V), and CoNC/BP (0.85?V). An accelerated durability test (ADT) on FeCoNC/BP indicated good durability over 35000 cycles. FeCoNC/BP also showed moderate ORR and ADT performance in acidic media. The macro/mesoporous N-doped carbon structures enhanced the mass transport properties of the dual Fe?Co active-sites. Therefore, modifying carbon supports with nonprecious metal catalysts may be a cost-effective-strategy for sustained electrochemical energy conversion.
Samireddi, S, Aishwarya V, Shown I, Muthusamy S, Unni SM, Wong K-T, Chen K-H, Chen L-C.
2021.
Synergistic Dual-Atom Molecular Catalyst Derived from Low-Temperature Pyrolyzed Heterobimetallic Macrocycle-N4 Corrole Complex for Oxygen Reduction. Small. 17:2103823., Number 46
AbstractAbstract A heterobimetallic corrole complex, comprising oxygen reduction reaction (ORR) active non-precious metals Co and Fe with a corrole-N4 center (PhFCC), is successfully synthesized and used to prepare a dual-atom molecular catalyst (DAMC) through subsequent low-temperature pyrolysis. This low-temperature pyrolyzed electrocatalyst exhibited impressive ORR performance, with onset potentials of 0.86 and 0.94 V, and half-wave potentials of 0.75 and 0.85 V, under acidic and basic conditions, respectively. During potential cycling, this DAMC displayed half-wave potential losses of only 25 and 5 mV under acidic and alkaline conditions after 3000 cycles, respectively, demonstrating its excellent stability. Single-cell Nafion-based proton exchange membrane fuel cell performance using this DAMC as the cathode catalyst showed a maximum power density of 225 mW cm−2, almost close to that of most metal–N4 macrocycle-based catalysts. The present study showed that preservation of the defined CoN4 structure along with the cocatalytic Fe–Cx site synergistically acted as a dual ORR active center to boost overall ORR performance. The development of DAMC from a heterobimetallic CoN4-macrocyclic system using low-temperature pyrolysis is also advantageous for practical applications.
Yang, J, Wang C-Y, Wang C-C, Chen K-H, Mou C-Y, Wu H-L.
2020.
Advanced nanoporous separators for stable lithium metal electrodeposition at ultra-high current densities in liquid electrolytes, 2020. Journal of Materials Chemistry A. 8(10):5095-5104.: The Royal Society of Chemistry
AbstractLithium metal anodes form a dendritic structure after cycling which causes an internal short circuit in flammable electrolytes and results in battery fires. Today's separators are insufficient for suppressing the formation of lithium dendrites. Herein, we report on the use of mesoporous silica thin films (MSTFs) with perpendicular nanochannels (pore size ∼5 nm) stacking on an anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator for advancing Li metal batteries. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows ultra-long term stability of Li plating/stripping in Li–Li cells at an ultra-high current density and capacity (10 mA cm−2 and 5 mA h cm−2). A significant improvement over the state-of-the-art separator is evaluated based on three performance indicators, e.g. cycle life, current density and capacity. In Li–Cu cells, the MSTF⊥AAO separator shows a coulombic efficiency of >99.9% at a current density of 10 mA cm−2 for more than 250 h of cycling. The separator gives improved rate capability in Li–LiFePO4 (LFP) batteries. The excellent performance of the MSTF⊥AAO separator is due to good wetting of electrolytes, straight nanopores with negative charges, uniform Li deposition and blocking the finest dendrite.
Shit, SC, Shown I, Paul R, Chen K-H, Mondal J, Chen L-C.
2020.
Integrated nano-architectured photocatalysts for photochemical CO2 reduction, 2020. Nanoscale. 12(46):23301-23332.: The Royal Society of Chemistry
AbstractRecent advances in nanotechnology, especially the development of integrated nanostructured materials, have offered unprecedented opportunities for photocatalytic CO2 reduction. Compared to bulk semiconductor photocatalysts, most of these nanostructured photocatalysts offer at least one advantage in areas such as photogenerated carrier kinetics, light absorption, and active surface area, supporting improved photochemical reaction efficiencies. In this review, we briefly cover the cutting-edge research activities in the area of integrated nanostructured catalysts for photochemical CO2 reduction, including aqueous and gas-phase reactions. Primarily explored are the basic principles of tailor-made nanostructured composite photocatalysts and how nanostructuring influences photochemical performance. Specifically, we summarize the recent developments related to integrated nanostructured materials for photocatalytic CO2 reduction, mainly in the following five categories: carbon-based nano-architectures, metal–organic frameworks, covalent-organic frameworks, conjugated porous polymers, and layered double hydroxide-based inorganic hybrids. Besides the technical aspects of nanostructure-enhanced catalytic performance in photochemical CO2 reduction, some future research trends and promising strategies are addressed.
Prem Kumar, DS, Tippireddy S, Ramakrishnan A, Chen K-H, Malar P, Mallik RC.
2019.
Thermoelectric and electronic properties of chromium substituted tetrahedrite, 2019. Semiconductor Science and Technology. 34(3):035017.: IOP Publishing
AbstractCr substituted tetrahedrites with the chemical formula Cu12−xCrxSb4S13 (x = 0.15, 0.25, 0.35, 0.5, 0.75, 1.0) have been synthesised for thermoelectric study. Cr substitutes at the Cu site to optimize the thermoelectric properties and achieve a higher figure of merit (zT). X-Ray diffraction (XRD) analysis revealed that the tetrahedrite is the major phase with minor impurity phases. Electron probe microanalysis (EPMA) shows the formation of tetrahedrite main phase with near stoichiometry and the presence of Cu3SbS4, CuSbS2 and Sb as secondary phases. X-ray photoelectron spectroscopy (XPS) shows the oxidation state of Cu, Sb and S as +1, +3 and −2, respectively, whereas for Cr, it could not be identified. Temperature-dependent magnetic susceptibility of sample x = 0.75 shows antiferromagnetic correlation originating from the Cr ion. The calculated effective magnetic moment of 2.83 μB per Cr atom indicates the presence of Cr+4 in this sample. The decrease in the electrical resistivity upon doping indicates the compensation of holes due to the substitution of Cr at the Cu site. But the x = 0.35 sample is not following the trend due to larger compensation of holes with an activation energy of 124.6 meV. The temperature-dependent behaviour of electrical resistivity shows the shift in the Fermi level from the valance band towards the band gap. The absolute Seebeck coefficient is positive throughout the temperature range and follows a similar trend as that of electrical resistivity, with the exception of the x = 0.35 sample. The electronic thermal conductivity reduces due to hole compensation caused by Cr substitution. Moreover, the substitution of Cr effectively reduces the lattice thermal conductivity due to point defect scattering of phonons. A maximum zT of 1.0 is achieved for sample x = 0.35 at 700 K.
Das, S, Valiyaveettil SM, Chen K-H, Suwas S, Mallik RC.
2019.
Thermoelectric properties of Mn doped BiCuSeO, 2019. Materials Research Express. 6(8):086305.: IOP Publishing
AbstractBiCuSeO is a promising thermoelectric material having earth-abundant non-toxic constituents and favourable thermoelectric properties like ultra-low thermal conductivity. In this study, Mn+2 has been introduced at the Bi+3 site to increase hole concentration as well as Seebeck coefficient, through aliovalent doping and magnetic impurity incorporation respectively. Samples were prepared through two-step solid state synthesis with the composition Bi1-xMnxCuSeO (x = 0.0, 0.04, 0.06, 0.08, 0.10 and 0.12). X-ray diffraction patterns confirmed the tetragonal (space group: P4/nmm) crystal structure of BiCuSeO as well as phase purity of the samples. The Seebeck coefficient and electrical resistivity had a decreasing trend with increasing doping fraction owing to the generation of charge carriers. The samples with x = 0.04 and 0.06 showed temperature independent Seebeck coefficient above 523 K, which is a signature of small polaron hopping. While the Seebeck coefficient of the samples with x = 0.08, 0.10 and 0.12 increased above 523 K due to the combination of localized and extended states. The thermal conductivity was dominated by the lattice part of the thermal conductivity. As a result of moderate Seebeck coefficient and low electrical resistivity, the highest power factor of 0.284 mW m−1-K2 was obtained for the Bi0.92Mn0.08CuSeO at 773 K, leading to a maximum zT of 0.4 at 773.
Ebrahimi, M, Samadi M, Yousefzadeh S, Soltani M, Rahimi A, Chou T-chin, Chen L-C, Chen K-H, Moshfegh AZ.
2017.
Improved Solar-Driven Photocatalytic Activity of Hybrid Graphene Quantum Dots/ZnO Nanowires: A Direct Z-Scheme Mechanism, 2017. ACS Sustainable Chemistry & EngineeringACS Sustainable Chemistry & Engineering. 5(1):367-375.: American Chemical Society
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Pathak, A, Chiou GR, Gade NR, Usman M, Mendiratta S, Luo T-T, Tseng TW, Chen J-W, Chen F-R, Chen K-H, Chen L-C, Lu K-L.
2017.
High-κ Samarium-Based Metal–Organic Framework for Gate Dielectric Applications. ACS Appl. Mater. Interfaces. 9(26):21872–21878.
Qorbani, M, Chou T-chin, Lee Y-H, Samireddi S, Naseri N, Ganguly A, Esfandiar A, Wang C-H, Chen L-C, Chen K-H, Moshfegh AZ.
2017.
Multi-porous Co3O4 nanoflakes @ sponge-like few-layer partially reduced graphene oxide hybrids: towards highly stable asymmetric supercapacitors. Journal of Materials Chemistry A. 5:12569-12577.
Sun, CL, Hsu YK, Lin YG, Chen KH, Bock C, MacDougall B, Wu X, Chen LC.
2009.
Ternary PtRuNi nanocatalysts supported on N-doped carbon nanotubes: deposition process, materials characterization, and electrochemistry. J. Electrochem. Soc.. 156:B1249-B1252.
Dhara*, S, Wu JJ, Mangama G, Bera S, Magudapathy P, Wu CT, Nair KGM, Kamaruddin M, Yu CC, Yang MH, Liu SC, Tyagi AK, Narashiman SV, Chen LC, Chen KH.
2007.
Long-range ferromagnetic ordering at room temperature in Co+ implanted TiO2 nanorods. Nanotechnology. 18:325705.