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802 results on '"Pan, Lun"'

214. IrO2Nanoparticle-Decorated Ir-Doped W18O49Nanowires with High Mass Specific OER Activity for Proton Exchange Membrane Electrolysis

Author

Yan, Tianqing, Chen, Shiyi, Sun, Wendi, Liu, Yuezheng, Pan, Lun, Shi, Chengxiang, Zhang, Xiangwen, Huang, Zhen-Feng, and Zou, Ji-Jun

Abstract

The oxygen evolution reaction (OER) severely limits the efficiency of proton exchange membrane (PEM) electrolyzers due to slow reaction kinetics. IrO2is currently a commonly used anode catalyst, but its large-scale application is limited due to its high price and scarce reserves. Herein, we reported a practical strategy to construct an acid OER catalyst where Iridium oxide loading and iridium element bulk doping are realized on the surface and inside of W18O49nanowires by immersion adsorption, respectively. Specifically, W0.7Ir0.3Oyhas an overpotential of 278 mV at 10 mA·cm–2in 0.1 M HClO4. The mass activity of 714.10 A·gIr–1at 1.53 V vs. the reversible hydrogen electrode (RHE) is 80 times that of IrO2, and it can run stably for 55 h. In the PEM water electrolyzer device, its mass activity reaches 3563.63 A·gIr–1at the cell voltage of 2.0 V. This improved catalytic performance is attributed to the following aspects: (1) The electron transport between iridium and tungsten effectively improves the electronic structure of the catalyst; (2) the introduction of iridium into W18O49by means of elemental bulk doping and nanoparticles supporting for the enhanced conductivity and electrochemically active surface area of the catalyst, resulting in extensive exposure of active sites and increased intrinsic activity; and (3) during the OER process, partial iridium elements in the bulk phase are precipitated, and iridium oxide is formed on the surface to maintain stable activity. This work provides a new idea for designing oxygen evolution catalysts with low iridium content for practical application in PEM electrolyzers.

Published
2023
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215. Tracking the Role of Defect Types in Co3O4Structural Evolution and Active Motifs during Oxygen Evolution Reaction

Author

Zhang, Rongrong, Pan, Lun, Guo, Beibei, Huang, Zhen-Feng, Chen, Zhongxin, Wang, Li, Zhang, Xiangwen, Guo, Zhiying, Xu, Wei, Loh, Kian Ping, and Zou, Ji-Jun

Abstract

Dynamic reconstruction of catalyst active sites is particularly important for metal oxide-catalyzed oxygen evolution reaction (OER). However, the mechanism of how vacancy-induced reconstruction aids OER remains ambiguous. Here, we use Co3O4with Co or O vacancies to uncover the effects of different defects in the reconstruction process and the active motifs relevant to alkaline OER. Combining in situ characterization and theoretical calculations, we found that cobalt oxides are converted to an amorphous [Co(OH)6] intermediate state, and then the mismatched rates of *OH adsorption and deprotonation lead to irreversible catalyst reconstruction. The stronger *OH adsorption but weaker deprotonation induced by O defects provides the driving force for reconstruction, while Co defects favor dehydrogenation and reduce the reconstruction rate. Importantly, both O and Co defects trigger highly OER-active bridge Co sites in reconstructed catalysts, of which Co defects induce a short Co–Co distance (3.38 Å) under compressive lattice stress and show the best OER activity (η10of 262 mV), superior to reconstructed oxygen-defected Co3O4-VO(η10of 300 mV) and defect-free Co3O4(η10of 320 mV). This work highlights that engineering defect-dependent reconstruction may provide a rational route for electrocatalyst design in energy-related applications.

Published
2023
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220. Manipulating Spin Polarization of Defected Co3O4 for Highly Efficient Electrocatalysis.

Author

Li, Yue, Wang, Tianzuo, Asim, Muhammad, Pan, Lun, Zhang, Rongrong, Huang, Zhen-Feng, Chen, Zhichao, Shi, Chengxiang, Zhang, Xiangwen, and Zou, Ji-Jun

Abstract

Electrocatalytic water splitting is limited by kinetics-sluggish oxygen evolution, in which the activity of catalysts depends on their electronic structure. However, the influence of electron spin polarization on catalytic activity is ambiguous. Herein, we successfully regulate the spin polarization of Co3O4 catalysts by tuning the concentration of cobalt defects from 0.8 to 14.5%. X-ray absorption spectroscopy spectra and density functional theory calculations confirm that the spin polarization of Co3O4 is positively correlated with the concentration of cobalt defects. Importantly, the enhanced spin polarization can increase hydroxyl group absorption to significantly decrease the Gibbs free energy change value of the OER rate-determining step and regulate the spin polarization of oxygen species through a spin electron-exchange process to easily produce triplet-state O2, which can obviously increase electrocatalytic OER activity. In specific, Co3O4-50 with 14.5% cobalt defects exhibits the highest spin polarization and shows the best normalized OER activity. This work provides an important strategy to increase the water splitting activity of electrocatalysts via the rational regulation of electron spin polarization. [ABSTRACT FROM AUTHOR]

Published
2022
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221. Synergy Promotion of Elemental Doping and Oxygen Vacancies in Fe2O3 Nanorods for Photoelectrochemical Water Splitting.

Author

Wang, Songbo, Meng, Chengzhen, Bai, Yanxiang, Wang, Yidan, Liu, Pengjie, Pan, Lun, Zhang, Lei, Yin, Zhen, and Tang, Na

Abstract

Photoelectrochemical (PEC) water splitting has been regarded as an ideal strategy to solve the current energy crisis and realize net-zero carbon dioxide emissions, and the key for an efficient PEC process is highly active photoanode catalysts. Herein, we developed a simple hydrothermal-calcination approach to fabricate Fe2O3 nanorods (NRs) doped with Ni2+, Ca2+, and Mg2+, respectively, which exhibited improved PEC performance than bare Fe2O3 NRs. The experimental results indicate that Ni2+, Ca2+, and Mg2+ were successfully doped into the lattice of Fe2O3, which can change the electronic structure of α-Fe2O3 and thus increase the density of charge carriers and reduce charge transfer resistance. Meanwhile, abundant oxygen vacancies were induced simultaneously with the Mg-doping process, which realize the synergy promotion of elemental doping and oxygen vacancies. Therefore, the optimized Mg-doped Fe2O3 NRs exhibited the highest photocurrent density of 0.763 mA·cm–2, which is 4.86-fold higher than that of the pure Fe2O3 NRs. This work indicates that the synergy of elemental doping and oxygen vacancies is an effective approach to improve the PEC performance of Fe2O3 NRs. [ABSTRACT FROM AUTHOR]

Published
2022
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222. Framework Zr Stabilized PtSn/Zr‐MCM‐41 as a Promising Catalyst for Non‐oxidative Ethane Dehydrogenation.

Author

Xu, Jisheng, Shi, Chengxiang, Zhang, Shuguang, Zheng, Qiancheng, Pan, Lun, Zhang, Xiangwen, and Zou, Ji‐Jun

Subjects
DEHYDROGENATION, MIXED oxide catalysts, ETHANES, CATALYST supports, CATALYSTS, METALS
Abstract

Comprehensive Summary: Non‐oxidative ethane dehydrogenation is a promising route to produce ethene. Herein, PtSn supported catalysts were investigated to achieve better ethane dehydrogenation performance by introduction of different Zr promoters, i.e., framework Zr and ZrO2, to mesoporous MCM‐41. In‐situ XRD, TEM and CO chemisorption show that aggregation of metal particles and phase segregation of Pt3Sn to Pt and PtSn3 at high temperature occur for PtSn/M, leading to bad ethane dehydrogenation activity. Strong interaction between ZrO2 and PtSn species, as proved by XPS, results in restrained metal particles, which promotes the initial reactivity. However, Pt phase generated on surface is disadvantageous for the desorption of produced ethene as indicated by CO‐IR and C3H6‐TPD, and pyridine‐IR and NH3‐TPD indicate strong acidity generated. Both deactivate the catalyst rapidly by deep dehydrogenation and coking. Moderate interaction between PtSn species and Si‐O‐Zr with much weaker acidity is formed when framework Zr is incorporated into MCM‐41, which benefits the dispersion of metal particles, formation of Pt3Sn/Pt species and stabilization of metal species from phase segregation. Outstanding initial ethane conversion and ethene selectivity of ca. 99% were achieved for the optimal PtSn/ZrM, which is more coking‐tolerant and stable by generating graphitic carbon mainly on support instead of active metals. [ABSTRACT FROM AUTHOR]

Published
2022
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228. 2020 Roadmap on gas-involved photo- and electro- catalysis

Author

Yang, Yulu, Tang, Yang, Jiang, Haomin, Chen, Yongmei, Wan, Pingyu, Fan, Maohong, Zhang, Rongrong, Ullah, Sana, Pan, Lun, Zou, Ji-Jun, Lao, Mengmeng, Sun, Wenping, Yang, Chao, Zheng, Gengfeng, Peng, Qiling, Wang, Ting, Luo, Yonglan, Sun, Xuping, Konev, Alexander S., Levin, Oleg V., Lianos, Panagiotis, Zhuofeng, Hu, Shen, Zhurui, Zhao, Qinglan, Wang, Ying, Todorova, Nadia, Trapalis, Christos, Sheridan, Matthew V., Wang, Haipeng, Zhang, Ling, Sun, Songmei, Wang, Wenzhong, and Ma, Jianmin

Published
2019
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235. Recent Progress on the Development of Carbon Nitride Based All‐Solid Z‐Scheme Photocatalyst for Solar Energy Conversion Applications.

Author

Zhang, Jing-Wen, Shi, Chengxiang, Mahmood, Nasir, Ai, Minhua, Pan, Lun, Huang, Zhen-Feng, and Zou, Ji-Jun

Subjects
SOLAR energy conversion, NITRIDES, ELECTRONIC band structure, CHARGE transfer, CHARGE carriers, SOLAR energy, ENERGY consumption
Abstract

The visible‐light responsive semiconductor carbon nitride (C3N4) exhibits suitable electronic band structure, rich sources of precursors, and high stability, which is exploited to satisfy energy demands. However, the photocatalytic efficiency of C3N4 is limited because of its low surface area and low separation and transfer efficiency of charge carriers. As Z‐scheme strategy can effectively help C3N4 overcome its instinct shortage, this review will outline the recent significant progress on the development of C3N4‐based all‐solid Z‐scheme photocatalysts for energy‐conversion applications including water splitting and CO2 reduction. In the beginning, the fundamental principles of Z‐scheme will be introduced, especially for all‐solid‐state system. Then, the comprehensive account of the development of C3N4‐based Z‐scheme photocatalysts are discussed. Finally, perspectives on the challenges and future directions at the forefront of Z‐scheme photocatalysts are provided. [ABSTRACT FROM AUTHOR]

Published
2022
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