bluuebunny/crossref_metadata_2025_split huggingface dataset:
MOF-Derived Nanoporous Carbon As an Efficient Bifunctional Oxygen Electrocatalyst for Erzabs
Authors: T Saranya , Mathialagan Kowsalya , Dixon Ditty , Bhaskar Aiswarya , Nishanthi S.T 
Published: November 2022

Zinc-air batteries are cost-effective batteries that possess a high energy density (1086 Wh Kg-1), compared to other conventional battery systems. In order to improve the electrochemical performance of electrically rechargeable zinc-air batteries (ERZABs), an effective bifunctional oxygen electrocatalyst is required. Hence, the development of non-noble metal bifunctional catalysts for ORR and OER is of prime importance. The transition metal-based catalysts have increasing demand since they are promising alternatives, in terms of cost and durability, to noble metal catalysts. Metal-organic frameworks (MOF) based catalysts show high catalytic activity due to adjustable pore size, ultra-high surface area, and structural designability[1].Increasing porosity can augment the catalytic activity by increasing the surface area, thereby enhancing the ORR kinetics.
In the present work, a CFZ-NPC (CoFeZn-MOF derived nanoporous carbon) was synthesized via hydrothermal method and investigated as a bifunctional catalyst for rechargeable zinc-air batteries[2]. The catalyst shows a high electrochemical activity towards oxygen reduction reaction with a half-wave potential of 830 mV vs. RHE and a comparable oxygen evolution activity (overpotential of 379 mV vs. RHE at 10 mA cm-2 ) with IrO2 (Over potential of 377 mV at 10 mA cm-2). The binder-free CFZ-NPC air electrode when applied into a Zinc-air battery system, delivers a low charge-discharge potential gap of 862 mV at 5 mA cm-2. Interestingly, the catalyst possesses an excellent electrochemical performance in the electrically rechargeable Zn-air battery over 1000 cycles at selected DOD for 157 h with a specific capacity of 890 mAh g(Zn)
-1 without much efficiency drop.
Financial support from Department of Science and Technology, Govt. of India under research grant number DST/TMD/MECSP/2K17/20 is gratefully acknowledged

References;

[1] Ren, Shuangshuang et al. 2020. “Bifunctional Electrocatalysts for Zn-Air Batteries: Recent Developments and Future Perspectives.” Journal of Materials Chemistry A 8(13): 6144–82.
[2] Tang, Jing et al. 2016. “Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nano porous Carbons.” Nature Publishing Group (April): 1-8.
Superionic Conducting Triple-Doped Stabilized Bismuth Oxide for High Performing Reversible Solid Oxide Cells
Authors: Yu Hyeongmin , Kim Doyeub , Jeong Incheol , Im Ha-Ni , Lee Kang Taek 
Published: November 2022

Reversible solid oxide cells (SOCs) have drawn much attention as alternative energy conversion and storage devices owing to their high efficiency and environmental benignity. However, considering their high operating temperature involves unwanted chemical reactions, thermal stress, and high system costs it is essential to lower their operating temperature for commercial feasibility. At reduced temperature, on the other hand, the catalytic activity of oxygen reduction reactions (ORRs), oxygen evolution reactions (OERs), and oxygen ionic transport are diminished due to their thermally activated nature. For example, the most widely used yttria-stabilized zirconia (YSZ) shows significantly decreased ionic conductivity at reduced temperature (e.g. 0.003 S/cm at 600 °C), which is not sufficient for high performing SOCs.
Among various alternative oxygen ionic conducting materials, rare-earth stabilized bismuth oxides have been well known as super ionic conductors which exhibit 30 times higher conductivity than that of YSZ. However, the ionic conductivity of stabilized bismuth oxides is significantly decreased due to their phase transformation from cubic phase to rhombohedral phase at 600 °C. In this regard, it is crucial to carefully utilize proper doping material for enhancing their stability while retaining their high ionic conductivity.
In this study, we newly developed stabilized bismuth oxide with superior ionic conductivity and durability at 600 °C via triple-doping strategy. Initial ionic conductivity of the stabilized bismuth oxide was maintained for more than 1000 hours at 600 °C with no phase transformation. This stabilized bismuth oxide was combined with conventional La0.8Sr0.2MnO3-
δ (LSM) as a novel oxygen electrode. Furthermore, a SOC with this novel air electrode showed high electrochemical performance both in the fuel cell (FC) and the electrolysis (EC) modes (e.g. 2.5 W/cm2 and 1.4 A/cm2 at 1.3V at 700 °C in the FC and the EC modes, respectively).
Degradation and Reactivation of Ni-Doped Strontium Iron Titanate Solid Oxide Cell Fuel Electrodes
Authors: Zhang Yubo , Schmauss Travis Anthony , Barnett Scott A 
Published: November 2022

Compared with conventional cermet solid oxide cell fuel electrodes, perovskite electrodes have the advantages of redox stability, coking resistance and sulfur resistance. Moreover, cation exsolution, where metal nanoparticles exsolve from the parent perovskite oxide under reducing conditions, has been shown to significantly enhance the electrochemical performance of the perovskite fuel electrodes due to the surface decoration of highly dispersed, catalytically active metal nanoparticles. Unfortunately, the phase transition of perovskite electrodes with time under different fuel conditions and its effect on their durability have not been fully understood. Furthermore, the phase and microstructure transformation of these exsolved perovskite electrodes under redox cycles still need more investigation.
Here durability test of Ni-doped strontium iron titanate (STFN) was conducted at 850oC under different fuel conditions and redox cycles were introduced during these life-tests. Degradation in both ohmic resistance (R0) and polarization resistance (Rp) was observed during aging in 97% H2 + 3% H2O, and the introduction of wet Ar after 240-hour aging successfully recovered some of the electrochemical performance of STFN. In-situ X-ray diffraction shows the formation of Ruddlesden-Popper phase together with Ni-Fe alloy exsolution upon exposing to 97% H2 + 3% H2O and the change in composition over time was also observed. Scanning electron microscopy also shows coarsening of exsolved nanoparticles and microstructural change of perovskite electrodes. Moreover, life tests of STFN were also conducted in 50% H2 + 50% H2O and 50% H2 + 50% H2O at 850oC. Despite the more Ni-rich exsolved nanoparticles due to the higher oxygen partial pressure, the durability was worse than that of 97% H2 + 3% H2O. The increased degradation rate was attributed to the microstructural change of the parent perovskite phase.
A-Site Doping Effect on the Performance of Sr2Fe1.4 Ni0.1Mo0.5O6-Δ Anodes for SOFCs
Authors: Li Haixia , Wang Wanhua , Park Ka-Young , Lee Taehee , Chen Fanglin (Frank) 
Published: November 2022

A site doped Sr2Fe1.4 Ni0.1Mo0.5O6-
δ (SFNM), i.e., La0.1Sr1.9Fe1.4Ni0.1Mo0.5O6-δ
(LSFNM) and Pr0.1Sr1.9Fe1.4Ni0.1Mo0.5O6-δ
(PSFNM) materials have been synthesized by sol-gel method in air and investigated as anode catalysts for intermediate temperature solid oxide fuel cells. Metallic nanoparticle-decorated ceramic anodes were prepared by in situ reduction of the LSFNM and PSFNM in H2 at 850 °C, forming Ruddlesden−Popper structure and FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the doped SFNM ceramic anode is greatly enhanced by A site La or Pr doping due to the ~50% decrease of the polarization resistance. The maximum power densities of the LSGM (320μm) electrolyte supported single cells with LSFNM and PSFNM as the anode reached 1.142 and 1.084 W cm−
2 in wet H2 at 850 °C, respectively. LSFNM and PSFNM are promising high-performance anodes for solid oxide fuel cells.
Acknowledgements: Financial support from the U.S. National Science Foundation (DMR–1832809) is greatly appreciated.
Surface-State-Controlled Fluence-Dependent Apce Behavior of p-GaAs-TiO2-Pt Water Reduction Photocathode
Authors: Suo Sa , Zhao Fengyi , Xu Zihao , Shi Haotian , Cai Zhi , Zhao Bofan , Hill Craig L , Musaev Djamaladdin G , Lian Tianquan 
Published: November 2022

The demand for reform in energy production and reduction in carbon dioxide emission lays emphasis on the development and mechanistic study of photocatalytic water splitting photoelectrodes. Understanding the bottlenecks of the photoelectrochemical (PEC) conversion efficiency in photocatalytic water splitting systems is essential to impart guidance to material selection and photoelectrode design. Absorbed photon-to-current conversion efficiency (APCE), which represents the fraction of absorbed photons converted into electrons in photocurrents, is the key metric in the evaluation of PEC performance. A large portion of studies have reported an illumination fluence-independent APCE under continuous wave (CW) illumination with power densities around 10~100 mW/cm2, whereas few cases have reported the fluence-dependent APCE performance. In the present work, we observe a rarely reported fluence-dependent APCE performance in the p-GaAs/5 nm TiO2/2 nm Pt photocathode under a low-excitation intensity regime. The APCE reaches close to unity at 0.005 mW/cm2 and gradually decreases to 60% at 1 mW/cm2. However, a theoretical explanation for this fluence-dependent APCE reduction is not established.
We develop a steady-state kinetic model with the least parameters to decipher such a phenomenon. In this model, the surface electrons in the GaAs/TiO2/Pt photocathode are consumed by three pathways: 1) transferred to redox active species in solution via the conduction band, 2) trapped into surface states that serve as the reaction sites, which competes with the electron-hole recombination at such surface states, and 3) directly recombining with the surface holes. The APCE decrease at higher illumination intensity is attributed to the increasing recombination between the GaAs holes and the TiO2 electrons caused by the saturation of surface sites. A detailed parametric survey shows that the interfacial electron transfer rate, ks, from the trap states to solution redox species is the only parameter that tunes the extent of the APCE reduction. With higher ks, APCE displays a smaller reduction in response to increasing fluences. Thus, the fluence-dependent feature of the APCE is an indicator that the surface reaction is the efficiency-determining step.
Through this work, we establish a kinetic model for the semiconductor photoelectrode with catalyst layer and successfully explain the cause to the fluence-dependent APCE performance. These significant findings can be universally applied to address the function of catalytic layer (nanoparticle or molecular) and surface modifier in hybrid photoelectrode systems that exhibit fluence-dependent APCE.
Intermetallic Water Splitting (Pre)Catalysts
Authors: Menezes Prashanth W. , Hausmann Jan Niklas , Driess Matthias 
Published: November 2022

The continuous increase in the population and industrial development has led to an increase in global energy demand. Most of the current primary energy consumption is obtained from the burning of fossil fuels that releases an enormous amount of greenhouse gases. Notably, hydrogen (H2) is a clean and eco-friendly fuel and has already shown its ability to be a promising substitute for fossil energy. One of the cleanest ways to produce H2 is by splitting of water by electrolysis.1 Recently, numerous inexpensive and robust catalysts based on transition metals (oxides, chalcogenides, pnictides, carbides, or alloys, etc.) have been developed for water splitting with reasonable activity.2 Despite the massive development of electrocatalysts for water splitting, huge challenges still exist for their use in practical application. Our current goals are to uncover new classes of suitable unconventional catalysts based on non-noble metals that can offer better overall catalytic efficiency for practical applications; to study their structural transformation, active sites, surface, and bulk structures; and to investigate the influence of precatalysts on the properties of the final catalyst.
In this context, intermetallic compounds have numerous advantages owing to their intriguing structural, chemical and physical properties, especially being catalytically active and electrically conductive at the same time and thus, making them an ideal class of materials for electrocatalytic applications.3 Using different approaches, we synthesized various classes of intermetallic materials (e.g., stannides, gallides, germanides, indates, silicides, etc.) with interesting structural and electronic features.4-5 Most of these materials exhibited remarkable electrocatalytic activity for water splitting, yielding considerably low overpotentials with enhanced long-term durability for both O2 and H2 generation in alkaline media. The active catalyst structure during each half-reaction (H2 and O2) and the correlation of the structure with the activity of the catalysts were revealed by a profound understanding of the system using in-situ and ex-situ techniques. This talk will provide a brief summary of the ongoing water splitting research as well as delve into selected examples of our recent work to pave the way to a concept-guided design system beyond water electrolysis (e.g., paired electrolysis).

References

[1] H Yang, M Driess, P. W. Menezes, Adv. Energy Mater. 2021, 11, 2102074.
[2] Z Chen, H Yang, Z Kang, M Driess, P. W. Menezes, Adv. Mater. 2022, 2108432.
[3] C. Walter, P. W. Menezes, M. Driess, Chem. Sci. 2021, 12, 8603.
[4] N. Hausmann, R. Beltrán-Suito, S. Mebs, V. Hlukhyy, T. F. Fässler, H. Dau, M. Driess, P. W. Menezes, Adv. Mater. 2021, 33, 2008823.
[5] B. Chakraborty, R. Beltrán-Suito, S. Garai, J. N. Hausmann, M. Driess, P. W. Menezes, Adv. Energy Mater. 2020, 10, 2001377.
(Invited) Crystal Engineering of Bismuth Vanadate for Enhanced Light-Driven Water Oxidation
Authors: Ng Yun Hau 
Published: November 2022

Photocatalytic and photoelectrochemical processes employing photoactive semiconductors are two key systems in harvesting sunlight for energy and environmental applications. Strategies have been formulated to improve the properties of the semiconductor for better performances. However, requirements to yield excellent performances are different in these two distinctive systems. Understanding of the underlying mechanism for the photoexcited charge transportation in relation to their photoactivities is of fundamental importance for rational design of high-performing photoactive materials, which may serve as a useful guideline for the fabrication of good photocatalysts or photoelectrodes toward sustainable solar fuels generation. Many photoactive semiconductors, including bismuth vanadate, are having inadequate charge transport properties such as low charge mobility, short lifetime, and slow surface kinetics. Standalone single photoactive semiconductors also faces the challenge of meeting the needs for large redox potentials with a sufficiently narrow bandgap for visible light absorption. Coupling two or more components into a photoactive composite may address some of these drawbacks by utilizing the strengths of the individual semiconductors. In this presentation, the charge transportation behavior of single component photoactive semiconductor based on bismuth vanadate, and the composite materials forming heterojunction with bismuth vanadate, will be examined and discussed (example of modulation of BiVO4 photocatalyst in
Figure 1
).1

Typically, crystal facet engineering, interfacing with non-photoactive secondary component, and narrowing the crystal size into quantum-confinement region, will be the three strategies to be shared with audience during the presentation. Preferential charge migration depending on the crystal facet has been reported in various photocatalysts. These promoted charge migration can be further boosted with spatially deposited cocatalysts on the selective redox sites. The manipulation of crystal facet allows the controlled electron transfer to induce 4-electron process (oxygen evolution) or 2-electron process (hydrogen peroxide evolution) in water oxidation. Nanosizing the bismuth vanadate into <10 nm region with distinctive yet interconnected crystal domains leads to the expansion of band structure. Conduction band of bismuth vanadate was expanded to energetic level capable of reducing proton into H2. The traditional O2-evolving bismuth vanadate is now demonstrating H2-producing properties.

Figure 1:
Time-resolved microwave conductivity (TRMC) spectroscopy signals measured for BiVO4 and its Power-law decay fittings.
Reference
1. H. Wu, R. Irani, K. Zhang, L. Jing, H. Dai, H. Y. Chung, F. F. Abdi, Y. H. Ng*, Unveiling Carrier Dynamics in Periodic Porous BiVO4 Photocatalyst for Enhanced Solar Water Splitting. ACS Energy Lett. 2021, 6, 3400-3407.

Figure 1
Modelling the Electrochemical Reduction of CO2 Under Gas-Liquid Channel Flow
Authors: Bagemihl Isabell , van Steijn Volkert , van Ommen J. 
Published: November 2022

Electrochemical reduction of CO2 using renewable energy sources is a promising avenue for sustainable production of bulk chemicals. The feasibility of electrochemical CO2 conversion has been demonstrated at lab scale, leading researchers to propose several reactor designs. However, CO2 electrolysis in aqueous systems is severely limited by mass transfer leading to performance parameters insufficient for industrial application. A strategy to enhance mass transfer is to actively introduce CO2 as a gas flow, while keeping diffusion paths between reactants and catalyst short, by separating the gas flow from the liquid electrolyte through a gas diffusion electrode. However, flooding, salt formation, or drying out of the gas diffusion electrode are common problems and present a major obstacle towards commercialisation. A promising reactor concept that enhances mass transfer without the complexity of a gas diffusion electrode is a structured reactor operated under gas-liquid Taylor flow: gas–liquid flow consisting of elongated bubbles in micro- or milli-channels. While this is a proven concept to enhance mass transfer for heterogeneous catalysis in flow cells, literature on this approach for electrochemical processes is scarce and the effect of process conditions on the reactor performance are poorly understood.
In this work, we propose a tubular cell design, inspired from the field of fuel cells, for CO2 electrolysis with a zero-gap membrane electrode assembly. We further, develop a simple analytical model revealing how reactor performance in terms of faradaic efficiency and current density is governed by the key features of Taylor flow. These features film thickness, bubble velocity, and volume fraction of CO2 bubbles over aqueous electrolyte, for a given cathode potential.
We find that the film thickness and the volume ratio of CO2/electrolyte fed to the reactor significantly affect the limiting current density and the faradaic efficiency. Additionally, we find industrially relevant performance with faradaic efficiencies (> 90 %) at current densities of up to 500 mA cm-2, when operating the reactor at elevated pressure beyond 5 bar. This demonstrates the general potential of this reactor concept to overcome mass transfer limitations in the field of electrolysis. We compare our predictions with numerical simulations, showing good agreement for a large window of operation conditions, illustrating when the simple predictive expressions for the current density and faradaic efficiency can be applied. We will discuss the importance of including interdependencies on the reactor scale to assess the economic viability of a reactor design and presents a tool to evaluate reactor design choices. We expect that the simple predictive expressions are instrumental in guiding experimental studies and reactor design choices, taking into account both technical and economic considerations.
Metal-Supported Solid Oxide Electrolysis Cells with Coatings to Suppress Chromium Migration
Authors: Tucker Mike C , Shen Fengyu , Welander Martha M 
Published: November 2022

High-temperature electrolysis (HTE) is an efficient technology for converting steam to hydrogen. The performance, durability, and applications of metal-supported solid oxide electrolysis cell technology developed at Lawrence Berkeley National Laboratory (LBNL) will be discussed. The unique LBNL symmetric cell architecture design, with thin zirconia ceramic backbones and electrolyte sandwiched between porous metal supports, offers a number of advantages over conventional all-ceramic cells, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability.
An inherent limitation of this design is the intimate contact between the electrode and the porous stainless steel, which is a source of chromium (Cr). Cr migrates from the support to the electrode during cell fabrication and operation, and reacts with the oxygen evolution electrocatalyst (LSCF). This Cr poisoning reduces performance and durability. To overcome this limitation, Cr-blocking coatings have been applied to the porous stainless steel. A variety of coating compositions and deposition techniques have been evaluated. The best coating dramatically reduces the amount of Cr detected in the electrode both after catalyst infiltration at 800°C and after 1000 h continuous operation at 700°C, Fig 1.
Other aspects of the MS-SOEC design and operation have been optimized for performance and durability. These include the infiltrated catalyst composition and processing, metal support structure, and operating temperature.

Figure 1
(Digital Presentation) Growth of Mn4+-Activated Red-Emitting Photoluminescent Crystals
Authors: Ji Haipeng 
Published: November 2022

Compared with Mn4+-activated polycrystalline phosphors in micro powder form, the Mn4+-activated red-emitting crystals with considerable size exhibit improved resistance to deterioration under water attack. Besides, large sized fluorescent crystal can be packaged on LED in the remote configuration. We recently developed a series of methods for growing Mn4+-doped red-emitting crystals which have different solubilities.
(1) For the fluoride hosts that have large solubility in acid solution such as (NH4)2SiF6, (NH4)2TiF6, K2TiF6, a series of centimeter-sized crystalline ingots were prepared by a cooling induced crystallization method (cooling from 20 °C to minus 40 °C). During cooling, the solubility decreases and the centimeter-scale Na2SiF6:Mn4+ ingots as well as the fluoride phosphors with similar physicochemical property including (NH4)2SiF6:Mn4+, (NH4)2TiF6:Mn4+ and K2TiF6:Mn4+ were successfully grown through the supersaturated crystallization process by cooling down.
(2) For the fluoride hosts that are slightly soluble such as BaTiF6, we firstly prepared BaTiOF4 as precursor, which is then mixed with K2MnF6 and gradually fluorinated in HF acid solution at room temperature. After a continuous feeding process, epitaxial growth of the BaTiF6:Mn4+ ended up with ingots up to a record-breaking length of 200−300 μm, which exhibit better water resistance than commercial K2SiF6:Mn4+ micro phosphor.
(3) For the oxide hosts that are insoluble such as MgAl2O4, we use the molten salt method, and by optimizing the type of molten salt to adjust the dissolution and migration of Mg2+/Al3+/Mn4+ ions in it, the MgAl2O4:Mn4+ crystals in tetragonal bipyramid shape with uniform size of 2−4 μm were prepared under relatively mild conditions at 950 °C. The phosphor exhibits a broadband emission peaking at 651 nm under the 450 nm excitation, which is the highest energy of the Mn4+
2E→4A2 transition energy in oxides.

Figure 1