Browsing by Author "Yu, Zhipeng"
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- Bifunctional atomically dispersed ruthenium electrocatalysts for efficient bipolar membrane water electrolysisPublication . Yu, Zhipeng; Si, Chaowei; Escobar-Bedia, Francisco Javier; LaGrow, Alec P.; Xu, Junyuan; Sabater, Maria J.; Amorim, Isilda; Araujo, Ana; Sousa, Juliana P. S.; Meng, Lijian; Faria, Joaquim Luis; Concepcion, Patricia; Li, Bo; Liu, LifengAtomically dispersed catalysts (ADCs) have recently drawn considerable interest for use in water electrolysis to produce hydrogen, because they allow for maximal utilization of metal species, particularly the expensive and scarce platinum group metals. Herein, we report the electrocatalytic performance of atomically dispersed ruthenium catalysts (Ru ADCs) with ultralow Ru loading (0.2 wt%). The as-obtained Ru ADCs (Ru (0.2)-NC) are active for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which only require a low overpotential (η) of 47.1 and 72.8 mV to deliver 10 mA cm−2 for HER in 0.5 M H2SO4 and 1.0 M KOH, respectively, and of 300 mV for OER in 1.0 M KOH, showing favorable bifunctionality. Density functional theory (DFT) calculations reveal that the Ru–N bonding plays an important role in lowering the energy barrier of the reactions, boosting the HER and OER activities. Furthermore, the bipolar membrane (BPM) water electrolysis using the bifunctional Ru (0.2)-NC as both HER and OER catalysts can afford 10 mA cm−2 under a low cell voltage of only 0.89 V, and does not show any performance decay upon 100 h continuous operation, showing great potential for energy-saving hydrogen production.
- Defective Ru-doped α-MnO2 nanorods enabling efficient hydrazine oxidation for energy-saving hydrogen production via proton exchange membranes at near-neutral pHPublication . Yu, Zhipeng; Si, Chaowei; Sabaté, Ferran; LaGrow, Alec P.; Tai, Zhixin; Diaconescu, Vlad Martin; Simonelli, Laura; Meng, Lijian; Sabater, Maria J.; Li, Bo; Liu, LifengProton exchange membrane water electrolysis (PEMWE) showes substantial advantages over the conventional alkaline water electrolysis (AWE) for power-to-hydrogen (PtH) conversion, given the faster response and wider dynamic current range of the PEMWE technology. However, PEMWE is currently still expensive due partly to the high voltage needed to operate at high current densities and inevitable usage of precious iridium/rutheniumbased catalysts to expedite the slow kinetics of the oxygen evolution reaction (OER) and to ensure sufficient durability under strongly acidic conditions. Herein, we report that ruthenium doped α-manganese oxide (Ru/ α-MnO2) nanorods show outstanding electrocatalytic performance toward the hydrazine (N2H4) oxidation reaction (HzOR) in near-neutral media (weak alkaline and weak acid), which can be used to replace the energydemanding OER for PEMWE. The as-prepared Ru/α-MnO2 is found to comprise abundant defects. When used to catalyze HzOR in the acid-hydrazine electrolyte (0.05 M H2SO4 + 0.5 M N2H4), it can deliver an anodic current density of 10 mA cm 2 at a potential as low as 0.166 V vs. reversible hydrogen electrode (RHE). Moreover, Ru/ α-MnO2 exhibits remarkable corrosion/oxidation resistance and remains electrochemically stable during HzOR for at least 1000 h. Theoretical calculations and experimental studies prove that Ru doping elongates the Mn–O bond and produces abundant cationic defects, which induces charge delocalization and significantly lowers material’s electrical resistance and overpotential, resulting in excellent HzOR catalytic activity and stability. The introduction of N2H4 significantly reduces the energy demand for hydrogen production, so that PEMWE can be accomplished under remarkably low voltages of 0.254 V at 10 mA cm 2 and 0.935 V at 100 mA cm 2 for a long term without notable degradation. This work opens a new avenue toward energy-saving PEMWE with earthabundant OER catalysts.
- Defective Ru-doped α-MnO2 nanorods enabling efficient hydrazine oxidation for energy-saving hydrogen production via proton exchange membranes at near-neutral pHPublication . Yu, Zhipeng; Si, Chaowei; Sabaté, Ferran; LaGrow, Alec P.; Tai, Zhixin; Diaconescu, Vlad Martin; Simonelli, Laura; Meng, Lijian; Sabater, Maria J.; Li, Bo; Liu, LifengProton exchange membrane water electrolysis (PEMWE) showes substantial advantages over the conventional alkaline water electrolysis (AWE) for power-to-hydrogen (PtH) conversion, given the faster response and wider dynamic current range of the PEMWE technology. However, PEMWE is currently still expensive due partly to the high voltage needed to operate at high current densities and inevitable usage of precious iridium/ruthenium-based catalysts to expedite the slow kinetics of the oxygen evolution reaction (OER) and to ensure sufficient durability under strongly acidic conditions. Herein, we report that ruthenium doped α-manganese oxide (Ru/α-MnO2) nanorods show outstanding electrocatalytic performance toward the hydrazine (N2H4) oxidation reaction (HzOR) in near-neutral media (weak alkaline and weak acid), which can be used to replace the energy-demanding OER for PEMWE. The as-prepared Ru/α-MnO2 is found to comprise abundant defects. When used to catalyze HzOR in the acid-hydrazine electrolyte (0.05 M H2SO4 + 0.5 M N2H4), it can deliver an anodic current density of 10 mA cm−2 at a potential as low as 0.166 V vs. reversible hydrogen electrode (RHE). Moreover, Ru/α-MnO2 exhibits remarkable corrosion/oxidation resistance and remains electrochemically stable during HzOR for at least 1000 h. Theoretical calculations and experimental studies prove that Ru doping elongates the Mn–O bond and produces abundant cationic defects, which induces charge delocalization and significantly lowers material’s electrical resistance and overpotential, resulting in excellent HzOR catalytic activity and stability. The introduction of N2H4 significantly reduces the energy demand for hydrogen production, so that PEMWE can be accomplished under remarkably low voltages of 0.254 V at 10 mA cm−2 and 0.935 V at 100 mA cm−2 for a long term without notable degradation. This work opens a new avenue toward energy-saving PEMWE with earth-abundant OER catalysts.
- Efficient hydrogen production by saline water electrolysis at high current densities without the interfering chlorine evolutionPublication . Yu, Zhipeng; Xu, Junyuan; Meng, Lijian; Liu, LifengSeawater electrolysis powered by renewable energy sources has been proposed to be a potentially cost-effective approach to green hydrogen production. However, the long-standing issue regarding the chlorine evolution reaction (CER) that deteriorates the performance of electrocatalysts and other components of electrolyzers has been impeding the market adoption of direct seawater electrolyzers. Herein, we demonstrate that coupling the cathodic hydrogen evolution reaction (HER) with the hydrazine oxidation reaction (HzOR) taking place at the anode enables the alkaline–saline water electrolysis to occur at a high current density without the unfavorable, interfering CER. Using bifunctional carbon paper supported Co–Ni–P nanowires (Co–Ni–P/CP) as the cathode and anode, we have accomplished hydrogen production in the alkaline–saline–hydrazine electrolyte at 500 mA cm−2 with a small cell voltage of only 0.533 V and outstanding stability of 80 hours with minimal degradation.
- Gold Single Atom Doped Defective Nanoporous Copper Octahedrons for Electrocatalytic Reduction of Carbon Dioxide to EthylenePublication . Zhao, Yang; Wang, Yanan; Yu, Zhipeng; Song, Chao; Wang, Jingwei; Huang, Haoliang; Meng, Lijian; Liu, Miao; Liu, LifengElectrocatalytic CO2 reduction into high-value multicarbon products offers a sustainable approach to closing the anthropogenic carbon cycle and contributing to carbon neutrality, particularly when renewable electricity is used to power the reaction. However, the lack of efficient and durable electrocatalysts with high selectivity for multicarbons severely hinders the practical application of this promising technology. Herein, a nanoporous defective Au1Cu single-atom alloy (DeAu1Cu SAA) catalyst is developed through facile low-temperature thermal reduction in hydrogen and a subsequent dealloying process, which shows high selectivity toward ethylene (C2H4), with a Faradaic efficiency of 52% at the current density of 252 mA cm−2 under a potential of −1.1 V versus reversible hydrogen electrode (RHE). In situ spectroscopy measurements and density functional theory (DFT) calculations reveal that the high C2H4 product selectivity results from the synergistic effect between Au single atoms and defective Cu sites on the surface of catalysts, where Au single atoms promote *CO generation and Cu defects stabilize the key intermediate *OCCO, which altogether enhances C−C coupling kinetics. This work provides important insights into the catalyst design for electrochemical CO2 reduction to multicarbon products.
- Highly Efficient and Stable Saline Water Electrolysis Enabled by Self‐Supported Nickel‐Iron Phosphosulfide Nanotubes With Heterointerfaces and Under‐Coordinated Metal Active SitesPublication . Yu, Zhipeng; Li, Yifan; Martin‐Diaconescu, Vlad; Simonelli, Laura; Ruiz Esquius, Jonathan; Amorim, Isilda; Araujo, Ana; Meng, Lijian; Faria, Joaquim Luis; Liu, LifengDirect seawater electrolysis is proposed as a potential low-cost approach to green hydrogen production, taking advantage of the vastly available seawater and large-scale offshore renewable energy being deployed. However, developing efficient, earth-abundant electrocatalysts that can survive under harsh corrosive conditions for a long time is still a significant technical challenge. Herein, the fabrication of a self-supported nickel-iron phosphosulfide (NiFeSP) nanotube array electrode through a two-step sulfurization/phosphorization approach is reported. The as-obtained NiFeSP nanotubes comprise abundant NiFeS/NiFeP heterointerfaces and under-coordinated metal sites, exhibiting outstanding activity and durability for the hydrogen and oxygen evolution reactions (HER and OER) in simulated alkaline-seawater solution (KOH + NaCl), with an overpotential of 380 (HER) and 260 mV (OER) at 500 mA cm-2 and outstanding durability of 1000 h. Theoretical calculations support the observed outstanding performance, showing that the heterointerface and under-coordinated metal sites synergistically lower the energy barrier of the rate-determining step reactions. The NiFeSP electrode also shows good catalytic performance for the urea oxidation reaction (UOR). By coupling UOR with HER, the bifunctional NiFeSP electrode pair can efficiently catalyze the overall urea-mediated alkaline-saline water electrolysis at 500 mA cm-2 under 1.938 V for 1000 h without notable performance degradation.
- Iridium–Iron Diatomic Active Sites for Efficient Bifunctional Oxygen ElectrocatalysisPublication . Yu, Zhipeng; Si, Chaowei; LaGrow, Alec P.; Tai, Zhixin; Caliebe, Wolfgang A.; Tayal, Akhil; Sampaio, Maria J.; Sousa, Juliana P. S.; Amorim, Isilda; Araujo, Ana; Meng, Lijian; Faria, Joaquim L.; Xu, Junyuan; Li, Bo; Liu, LifengDiatomic catalysts, particularly those with heteronuclear active sites, have recently attracted considerable attention for their advantages over single-atom catalysts in reactions involving multielectron transfers. Herein, we report bimetallic iridium−iron diatomic catalysts (IrFe−N−C) derived from metal−organic frameworks in a facile wet chemical synthesis followed by postpyrolysis. We use various advanced characterization techniques to comprehensively confirm the atomic dispersion of Ir and Fe on the nitrogen-doped carbon support and the presence of atomic pairs. The asobtained IrFe−N−C shows substantially higher electrocatalytic performance for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) when compared to the single-atom counterparts (i.e., Ir−N−C and Fe−N−C), revealing favorable bifunctionality. Consequently, IrFe−N−C is used as an air cathode in zinc− air batteries, which display much better performance than the batteries containing commercial Pt/C + RuO2 benchmark catalysts. Our synchrotron-based X-ray absorption spectroscopy experiments and density functional theory (DFT) calculations suggest that the IrFe dual atoms presumably exist in an IrFeN6 configuration where both Ir and Fe coordinates with four N atoms and two N atoms are shared by the IrN4 and FeN4 moieties. Furthermore, the Fe site contributes mainly to the ORR, while the Ir site plays a more important role in the OER. The dual-atom sites work synergistically, reducing the energy barrier of the rate-determining step and eventually boosting the reversible oxygen electrocatalysis. The IrFe−N−C catalysts hold great potential for use in various electrochemical energy storage and conversion devices.
- Lithium–copper alloy embedded in 3D porous copper foam with enhanced electrochemical performance toward lithium metal batteriesPublication . Lu, Ziyu; Tai, Zhixin; Yu, Zhipeng; LaGrow, Alec P.; Bondarchuk, Oleksandr; Sousa, Juliana P.S.; Meng, Lijian; Peng, Zhijian; Liu, LifengSuppressing dendrite growth and accommodating volume change, among others, are the main challenges for lithium (Li) metal anode to be used in rechargeable Li batteries. The commercial macroporous copper (Cu) foam current collector may only tackle these challenges to a little extent, and it is usually unable to provide sufficient Li nucleation sites, leading to rapidly increased polarization and unstable cycling performance. Herein, we report a three-dimensional composite anode comprising Li–Cu alloy melt-cast on a commercial Cu foam (CF) current collector (Li–Cu/CF), which can be converted to a unique architecture consisting of Li metal supported by an interconnected CuLix alloy nanowire network formed because of the phase separation, when the molten Li–Cu alloy cools down and gets solidified. Compared to the bare Li foil, the Li–Cu/CF anode shows a smaller polarization and better cycle stability in the carbonate electrolyte at various current densities ranging from 1 to 5 mA/cm2 and is free from dendrite growth upon repeated Li plating/stripping. This can be attributed to the low Li nucleation overpotential and high Coulombic efficiency (96%) during Li plating on and stripping from the thus-obtained hierarchically structured CF collector, as well as the higher proportion of Li2O relative to LiF in the solid-electrolyte interphase layer. Moreover, when assembled in a full cell paired with the LiFePO4 cathode, the Li–Cu/CF anode also exhibits much better rate capability and cycle performance than the bare Li foil. Our work provides a new convenient approach to construct a dendrite-free Li metal anode that can be potentially deployed in the next-generation high energy density rechargeable Li batteries.
- Sulfur and phosphorus co-doped FeCoNiCrMn high-entropy alloys as efficient sulfion oxidation reaction catalysts enabling self-powered asymmetric seawater electrolysisPublication . Yu, Zhipeng; Boukhvalov, Danil W.; Tan, Hao; Xiong, Dehua; Feng, Chuangshi; Wang, Jingwei; Wang, Wei; Zhao, Yang; Xu, Kaiyang; Su, Weifeng; Xiang, Xinyi; Lin, Fei; Huang, Haoliang; Zhang, Fuxiang; Zhang, Lei; Meng, Lijian; Liu, LifengSeawater electrolysis (SWE) represents a promising approach to green hydrogen (H2) production but currently faces substantial challenges such as the interference of chlorine chemistry and high energy consumption. In this work, we demonstrate that by replacing the energy-demanding oxygen evolution reaction (OER) with the sulfion oxidation reaction (SOR) and by implementing the concept of bipolar membrane (BPM) electrolysis in an acid-base dual electrolyte system, not only can the notorious chlorine evolution reaction (CER) be completely circumvented, but the energy consumption of SWE be significantly reduced. To do so, we develop a sulfur and phosphorus co-doped FeCoNiCrMn high entropy alloy (HEA-SP) catalyst, which shows good electrocatalytic performance for the SOR in alkaline-saline water. This can be attributed to the abundant lattice defects and strains in HEA-SP, leading to a high density of active sites and an optimized electronic structure favorable for the SOR. Moreover, density functional theory calculations and in situ Raman spectroscopy characterization reveal the crucial role of imperfect sulfur coverage on the HEA in facilitating the formation of Sx clusters during the SOR. Using the HEA-SP as anode catalysts, the SOR-assisted SWE only needs electrical energy of 0.253 kWh to produce one cubic meter of H2 at 100 mA cm−2, in the presence of a BPM. Impressively, chlorine-free H2 production from seawater and upgrading of sulfions to valuable sulfur can occur simultaneously and spontaneously at 10 mA cm−2, highlighting the great potential of the HEA-SP catalysts and the asymmetric cell design to enable energy- and cost-effective seawater electrolysis.