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Journal Article
Lien, H-T, Chang S-T, Chen P-T, Wong DP, Chang Y-C, Lu Y-R, Dong C-L, Wang C-H, Chen K-H, Chen L-C.  2020.  Probing the active site in single-atom oxygen reduction catalysts via operando X-ray and electrochemical spectroscopy, 2020. 11(1):4233. AbstractWebsite

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–Nx/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. Our results revealed the preferential adsorption of oxygen at the Co2+ center, with end-on coordination forming a Co2+-oxo species. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, corroborated with first-principle calculations, 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.

Chen, J-C, Hsiao Y-R, Liu Y-C, Chen P-Y, Chen K-H.  2019.  Polybenzimidazoles containing heterocyclic benzo[c]cinnoline structure prepared by sol-gel process and acid doping level adjustment for high temperature PEMFC application, 2019. 182:121814. AbstractWebsite

Polybenzimidazoles containing heterocyclic benzo[c]cinnoline structure are synthesized from 3,8-benzo[c]cinnoline dicarboxylic acid, terephthalic acid and 3,3′-diaminobenzidine. Their membranes are prepared by sol-gel process, involving the conversion of polymer solution in polyphosphoric acid to phosphoric acid. The acid doping levels of the as-prepared membranes increase as the contents of benzo[c]cinnoline increase, indicating good interaction between phosphoric acid and benzo[c]cinnoline structure. The as-prepared membranes with high acid doping levels might lead to the dissolution of membranes in phosphoric acid at temperature higher than 120 °C. A new method is proposed to adjust acid doping levels by immersing the as-prepared membranes in diluted phosphoric acid solutions of various concentrations. The adjusted membranes (acid doping levels around 30 PA RU−1) exhibit enhanced mechanical properties with tensile strength in the range of 4.1–5.2 MPa. The proton conductivity of adjusted membranes maintain at 0.15–0.17 S cm−1 at 160 °C under ambient atmosphere without humidification. The single cells based on the adjusted membranes exhibit open circuit voltages and peak power densities from 0.89 to 0.91 V and 691–1253 mW cm−2 at 160 °C, respectively. Compared to other polybenzimidazole membranes prepared by sol-gel process, the adjusted polybenzimidazoles show higher mechanical strength and better single cell performance.

Lin, CH, Chen RS, Lin YK, Wang SB, Chen LC, Chen KH, Wen MC, Chou MMC, Chang L.  2017.  Photoconduction properties and anomalous power-dependent quantum efficiency in non-polar ZnO epitaxial films grown by chemical vapor deposition. APPLIED PHYSICS LETTERS . 110:052101.
Huang, H-C, Chang S-T, Hsu H-C, Du H-Y, Wang C-H, Chen L-C, Chen K-H.  2017.  Pyrolysis of Iron–Vitamin B9 As a Potential Nonprecious Metal Electrocatalyst for Oxygen Reduction Reaction. Search Results ACS Sustainable Chemistry & Engineering. 5 (4):2897–2905.
Du, HY, Yang CS, Hsu H-C, Huang HC, Chang ST, Wang C-H, Chen J-C, Chen KH, Chen LC.  2015.  Pulsed electrochemical deposition of Pt NPs on polybenzimidazole-CNT hybrid electrode for high-temperature proton exchange membrane fuel cells. International Journal of Hydrogen Energy. 40:14398.
Huang, YF, Chen CY, Chen LC, Chen KH, Chattopadhyay S.  2014.  Plasmon management in index engineered 2.5D hybrid nanostructures for SERS. NPG Asia Materials. 6:e123.
Wong, DP, Lien HT, Chen YT, Chen KH, Chen LC.  2012.  Patterned growth of nanocrystalline silicon thin films through magnesiothermic reduction of soda lime glass. Green Chemistry. 14:896-900.
Lin*, YG, Lin* CK, Miller JT, Hsu YK, Chen YC, Chen LC, Chen KH.  2012.  Photochemically active reduced graphene oxide with controllable oxidation level. RSC Advances. 2:11258-11562.
Chen, RS, Tsai HY, Huang YS, Chen YT, Chen LC, Chen KH.  2012.  Photoconduction efficiencies in GaN nanowires grown by chemical vapor deposition and molecular beam epitaxy: acomparison study. Appl. Phys. Lett.. 101:113109.
Lin, YG, Hsu YK, Wang SB, Chen YC, Chen LC, Chen KH.  2012.  Plasmonic Ag@Ag3PO4 Nanoparticle Photosensitized ZnO Nanorod-Array Photoanodes for Water Oxidation. Energy & Environ. Sci.. 5:8917-8922.
Karlsson, KF, Amloy S, Chen YT, Chen KH, Hsu HC, Hsiao CL, Chen LC, Holtz PO.  2012.  Polarized emission and excitonic fine structure energies of InGaN quantum dots. Physica B-Condensed Matter. 407:1553.
Huang, H-C, Shown I, Chang S-T, Hsu H-C, Du H-Y, Kuo M-C, Wong K-T, Wang S-F, Wang C-H, Chen L-C, Chen K-H.  2012.  Pyrolyzed Cobalt Corrole as a Potential Non-Precious Catalyst for Fuel Cells. Adv. Funct. Mater.. 22:3500–3508.
Pao, C-W, Wu C-T, Tsai H-M, Liu Y-S, Chang C-L, Pong WF, Chiou J-W, Chen C-W, Hu M-S, Chu M-W, Chen L-C, Chen C-H, Chen K-H, Wang S-B, Chang S-J, Tsai M-H, Lin H-J, Lee J-F, Guo J-H.  2011.  Photoconduction and the electronic structure of silica nanowires embedded with gold nanoparticles. Phys. Rev. B. 84:165412.
R. S. Chen*, Yang TH, Chen HY, Chen LC, Chen* KH, Yang YJ, Su CH, Lin CR.  2011.  Photoconduction mechanism of oxygen sensitization in InN nanowires. Nanotechnology. 22:425702.
Hwang, JS, Kao MC, Shiu JM, Fan CN, Ye SC, Yu WS, Lin TY, Chattopadhyay S, Chen LC, Chen KH.  2011.  Photocurrent mapping in high efficiency radial p-n junction silicon nanowire solar cells using atomic force microscopy. J. Phys. Chem. C. 115:21981-21986.
Amloy, S, Chen YT, Karlsson KF, Chen KH, Hsu HC, Hsiao CL, C.Chen L, Holtz* PO.  2011.  Polarization resolved fine structure splitting of zero-dimensional InGaN excitons. Phys. Rev. B. 83:201307.
Hu, MS, Kuo CC, Wu CT, Chen CW, Ang PK, Loh KP, Chen KH, Chen LC.  2011.  The production of SiC nanowalls sheathed with a few layers of strained graphene and their use in heterogeneous catalysis and sensing applications. Carbon. 49:4911-4919.
Huang, HM, Chen RS, Chen HY, Liu TW, Kuo CC, Chen CP, Hsu HC, Chen LC, Chen* KH, Yang YJ.  2010.  Photoconductivity in single AlN nanowires by sub-bandgap excitation. Appl. Phys. Lett.. 96:062104.
Wang, CH, Hsu HC, Chang ST, Du HY, Wu CH, Shih HC, Chen LC, Chen* KH.  2010.  Platinum nanoparticles embedded in nitrogen-containing complexes for high methanol-tolerant oxygen reduction activity. J. Mater. Chem.. 20:7551-7557.
and J. S. Hwang*, Chen KY, Syu WS, Chen SW, Kuo CW, Syu WY, Lin TY, Chiang HP, Chattopadhyay S, Chen KH, Chen LC.  2010.  Preparation of silver nano-particle decorated silica nanowires on quartz as reusable versatile nano-structured surface-enhanced Raman scattering substrates. Nanotechnology. 21:025502.
Wright, JS, Lim W, Gila BP, Pearton* SJ, Ren F, Lai WT, Chen LC, Hu MS, Chen KH.  2009.  Pd-catalyzed hydrogen sensing with InN nanobelts. J. Vac. Sci. Technol.. B 27:L8-10.
Hsiao, CL, Hsu HC, Chen* LC, Wu CT, Chen CW, Chen M, Tu LW, Chen KH.  2007.  Photoluminescence spectroscopy of nearly defect-free InN microcrystals exhibiting nondegenerate semiconductor behaviors. Appl. Phys. Lett.. 91:181912.
Hwang*, JS, Hu ZS, Lu TY, Chen LW, Chen SW, Lin TY, Hsiao CL, Chen KH, Chen LC.  2006.  Photo-assisted local oxidation of GaN using an atomic force microscope. Nanotechnology. 17:3299-3303.
Chen*, CW, Huang CC, Lin YY, Su WF, Chen* LC, Chen KH.  2006.  Photoconductivity and highly selective UV sensing features of amorphous silicon carbon nitride thin films. Appl. Phys. Lett.. 88:073515-(1-3).
Hu, MS, Chen HL, Shen CH, Hong LS, Huang BR, Chen KH, Chen* LC.  2006.  Photosensitive gold nanoparticle-embedded dielectric nanowires. Nature Materials. 5:102-106.