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1,420 result(s) for "639/638/675"
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Low-temperature hydrogen production from water and methanol using Pt/α-MoC catalysts
As an alternative vehicle fuel, hydrogen can be generated in situ from methanol and water—a process that is shown here to occur under mild conditions using a catalyst that comprises platinum atomically dispersed on an α-molybdenum carbide substrate. Hydrogen power Fuel cells running on hydrogen are attractive alternative power supplies. One approach to ensuring safe storage and transportation of the required hydrogen is its in situ release from a stable liquid such as inexpensive methanol. Lili Lin et al . report that platinum atomically dispersed on an α-molybdenum carbide substrate is a very effective catalyst for the production of hydrogen from methanol and water under mild conditions. Although long-term stability remains to be tested and optimized, the exceptional performance of this system—which is attributed to the active involvement of the substrate and the synergy between it and platinum—meets the requirements for state-of-the-art fuel-cell vehicle applications. Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen are attractive alternative power supplies for a range of applications 1 , 2 , 3 , with in situ release of the required hydrogen from a stable liquid offering one way of ensuring its safe storage and transportation 4 , 5 before use. The use of methanol is particularly interesting in this regard, because it is inexpensive and can reform itself with water to release hydrogen with a high gravimetric density of 18.8 per cent by weight. But traditional reforming of methanol steam operates at relatively high temperatures (200–350 degrees Celsius) 6 , 7 , 8 , so the focus for vehicle and portable PEMFC applications 9 has been on aqueous-phase reforming of methanol (APRM). This method requires less energy, and the simpler and more compact device design allows direct integration into PEMFC stacks 10 , 11 . There remains, however, the need for an efficient APRM catalyst. Here we report that platinum (Pt) atomically dispersed on α-molybdenum carbide (α-MoC) enables low-temperature (150–190 degrees Celsius), base-free hydrogen production through APRM, with an average turnover frequency reaching 18,046 moles of hydrogen per mole of platinum per hour. We attribute this exceptional hydrogen production—which far exceeds that of previously reported low-temperature APRM catalysts—to the outstanding ability of α-MoC to induce water dissociation, and to the fact that platinum and α-MoC act in synergy to activate methanol and then to reform it.
Lithium extraction from low-quality brines
In the quest for environmental sustainability, the rising demand for electric vehicles and renewable energy technologies has substantially increased the need for efficient lithium extraction methods. Traditional lithium production, relying on geographically concentrated hard-rock ores and salar brines, is associated with considerable energy consumption, greenhouse gas emissions, groundwater depletion and land disturbance, thereby posing notable environmental and supply chain challenges. On the other hand, low-quality brines—such as those found in sedimentary waters, geothermal fluids, oilfield-produced waters, seawater and some salar brines and salt lakes—hold large potential owing to their extensive reserves and widespread geographical distribution. However, extracting lithium from these sources presents technical challenges owing to low lithium concentrations and high magnesium-to-lithium ratios. This Review explores the latest advances and continuing challenges in lithium extraction from these demanding yet promising sources, covering a variety of methods, including precipitation, solvent extraction, sorption, membrane-based separation and electrochemical-based separation. Furthermore, we share perspectives on the future development of lithium extraction technologies, framed within the basic principles of separation processes. The aim is to encourage the development of innovative extraction methods capable of making use of the substantial potential of low-quality brines. Precipitation, solvent extraction, sorption, membrane-based separation and electrochemical-based separation are described as promising methods for extracting lithium from low-quality brines, which have extensive reserves and widespread geographical distributions.
The future of low-temperature carbon dioxide electrolysis depends on solving one basic problem
Carbonate formation is the primary source of energy and carbon losses in low-temperature carbon dioxide electrolysis. Realigning research priorities to address the carbonate problem is essential if this technology is to become a viable option for renewable chemical and fuel production. Low-temperature carbon dioxide electrolysis is an attractive process for sustainable fuel synthesis, but current systems suffer from low efficiency. In this comment, authors discuss the limitations arising from the reaction between carbon dioxide and hydroxide, highlighting the need for new research to address this fundamental problem.
A non-academic perspective on the future of lithium-based batteries
In the field of lithium-based batteries, there is often a substantial divide between academic research and industrial market needs. This is in part driven by a lack of peer-reviewed publications from industry. Here we present a non-academic view on applied research in lithium-based batteries to sharpen the focus and help bridge the gap between academic and industrial research. We focus our discussion on key metrics and challenges to be considered when developing new technologies in this industry. We also explore the need to consider various performance aspects in unison when developing a new material/technology. Moreover, we also investigate the suitability of supply chains, sustainability of materials and the impact on system-level cost as factors that need to be accounted for when working on new technologies. With these considerations in mind, we then assess the latest developments in the lithium-based battery industry, providing our views on the challenges and prospects of various technologies. In the field of lithium-based batteries, there is often a divide between academic research and industrial needs. Here, the authors present a view on applied research to help bridge academia and industry, focusing on metrics and challenges to be considered for the development of practical batteries.
Roll-to-roll gravure-printed flexible perovskite solar cells using eco-friendly antisolvent bathing with wide processing window
Driven by recent improvements in efficiency and stability of perovskite solar cells (PSCs), upscaling of PSCs has come to be regarded as the next step. Specifically, a high-throughput, low-cost roll-to-roll (R2R) processes would be a breakthrough to realize the commercialization of PSCs, with uniform formation of precursor wet film and complete conversion to perovskite phase via R2R-compatible processes necessary to accomplish this goal. Herein, we demonstrate the pilot-scale, fully R2R manufacturing of all the layers except for electrodes in PSCs. Tert-butyl alcohol (tBuOH) is introduced as an eco-friendly antisolvent with a wide processing window. Highly crystalline, uniform formamidinium (FA)-based perovskite formation via tBuOH:EA bathing was confirmed by achieving high power conversion efficiencies (PCEs) of 23.5% for glass-based spin-coated PSCs, and 19.1% for gravure-printed flexible PSCs. As an extended work, R2R gravure-printing and tBuOH:EA bathing resulted in the highest PCE reported for R2R-processed PSCs, 16.7% for PSCs with R2R-processed SnO 2 /FA-perovskite, and 13.8% for fully R2R-produced PSCs. Driven by recent improvement in efficiency and stability of perovskite solar cells, the next step toward commercialisation is upscaling. Here, the authors demonstrate pilot-scale fully roll-to-roll manufacturing of flexible perovskite solar cells through gravure-printing and antisolvent bathing.
Boosting electrocatalytic CO2–to–ethanol production via asymmetric C–C coupling
Electroreduction of carbon dioxide (CO 2 ) into multicarbon products provides possibility of large-scale chemicals production and is therefore of significant research and commercial interest. However, the production efficiency for ethanol (EtOH), a significant chemical feedstock, is impractically low because of limited selectivity, especially under high current operation. Here we report a new silver–modified copper–oxide catalyst (dCu 2 O/Ag 2.3% ) that exhibits a significant Faradaic efficiency of 40.8% and energy efficiency of 22.3% for boosted EtOH production. Importantly, it achieves CO 2 –to–ethanol conversion under high current operation with partial current density of 326.4 mA cm −2 at −0.87 V vs reversible hydrogen electrode to rank highly significantly amongst reported Cu–based catalysts. Based on in situ spectra studies we show that significantly boosted production results from tailored introduction of Ag to optimize the coordinated number and oxide state of surface Cu sites, in which the * CO adsorption is steered as both atop and bridge configuration to trigger asymmetric C–C coupling for stablization of EtOH intermediates. It is of high interest to convert CO 2 into valuable ethanol product. Here the authors demonstrate the asymmetric C-C coupling triggered on Ag-modified oxide-derived Cu sites can accelerate and steer the reaction pathway for ethanol production with high faradaic efficiency and current density.
Insights into the activity of nickel boride/nickel heterostructures for efficient methanol electrooxidation
Designing efficient catalysts and understanding the underlying mechanisms for anodic nucleophile electrooxidation are central to the advancement of electrochemically-driven technologies. Here, a heterostructure of nickel boride/nickel catalyst is developed to enable methanol electrooxidation into formate with a Faradaic efficiency of nearly 100%. Operando electrochemical impedance spectroscopy and in situ Raman spectroscopy are applied to understand the influence of methanol concentration in the methanol oxidation reaction. High concentrations of methanol inhibit the phase transition of the electrocatalyst to high-valent electro-oxidation products, and electrophilic oxygen species (O* or OH*) formed on the electrocatalyst are considered to be the catalytically active species. Additional mechanistic investigation with density functional theory calculations reveals that the potential-determining step, the formation of *CH 2 O, occurs most favorably on the nickel boride/nickel heterostructure rather than on nickel boride and nickel. These results are highly instructive for the study of other nucleophile-based approaches to electrooxidation reactions and organic electrosynthesis. Understanding the role of active sites in electrooxidation reactions is important yet challenging. Here, the authors use operando spectroscopies to monitor the effect of methanol concentration on Ni 3 B/Ni heterostructures during formate production.
A membrane-based seawater electrolyser for hydrogen generation
Electrochemical saline water electrolysis using renewable energy as input is a highly desirable and sustainable method for the mass production of green hydrogen 1 – 7 ; however, its practical viability is seriously challenged by insufficient durability because of the electrode side reactions and corrosion issues arising from the complex components of seawater. Although catalyst engineering using polyanion coatings to suppress corrosion by chloride ions or creating highly selective electrocatalysts has been extensively exploited with modest success, it is still far from satisfactory for practical applications 8 – 14 . Indirect seawater splitting by using a pre-desalination process can avoid side-reaction and corrosion problems 15 – 21 , but it requires additional energy input, making it economically less attractive. In addition, the independent bulky desalination system makes seawater electrolysis systems less flexible in terms of size. Here we propose a direct seawater electrolysis method for hydrogen production that radically addresses the side-reaction and corrosion problems. A demonstration system was stably operated at a current density of 250 milliamperes per square centimetre for over 3,200 hours under practical application conditions without failure. This strategy realizes efficient, size-flexible and scalable direct seawater electrolysis in a way similar to freshwater splitting without a notable increase in operation cost, and has high potential for practical application. Importantly, this configuration and mechanism promises further applications in simultaneous water-based effluent treatment and resource recovery and hydrogen generation in one step. An efficient and scalable direct seawater electrolysis method for hydrogen production that addresses the side-reaction and corrosion problems associated with using seawater instead of pure water is demonstrated.
Challenges to developing materials for the transport and storage of hydrogen
Hydrogen has the highest gravimetric energy density of any energy carrier and produces water as the only oxidation product, making it extremely attractive for both transportation and stationary power applications. However, its low volumetric energy density causes considerable difficulties, inspiring intense efforts to develop chemical-based storage using metal hydrides, liquid organic hydrogen carriers and sorbents. The controlled uptake and release of hydrogen by these materials can be described as a series of challenges: optimal properties fall within a narrow range, can only be found in few materials and often involve important trade-offs. In addition, a greater understanding of the complex kinetics, mass transport and microstructural phenomena associated with hydrogen uptake and release is needed. The goal of this Perspective is to delineate potential use cases, define key challenges and show that solutions will involve a nexus of several subdisciplines of chemistry, including catalysis, data science, nanoscience, interfacial phenomena and dynamic or phase-change materials. Hydrogen, which possesses the highest gravimetric energy density of any energy carrier, is attractive for both mobile and stationary power, but its low volumetric energy density poses major storage and transport challenges. This Perspective delineates potential use cases and defines the challenges facing the development of materials for efficient hydrogen storage.
Operando studies reveal active Cu nanograins for CO2 electroreduction
Carbon dioxide electroreduction facilitates the sustainable synthesis of fuels and chemicals 1 . Although Cu enables CO 2 -to-multicarbon product (C 2+ ) conversion, the nature of the active sites under operating conditions remains elusive 2 . Importantly, identifying active sites of high-performance Cu nanocatalysts necessitates nanoscale, time-resolved operando techniques 3 – 5 . Here, we present a comprehensive investigation of the structural dynamics during the life cycle of Cu nanocatalysts. A 7 nm Cu nanoparticle ensemble evolves into metallic Cu nanograins during electrolysis before complete oxidation to single-crystal Cu 2 O nanocubes following post-electrolysis air exposure. Operando analytical and four-dimensional electrochemical liquid-cell scanning transmission electron microscopy shows the presence of metallic Cu nanograins under CO 2 reduction conditions. Correlated high-energy-resolution time-resolved X-ray spectroscopy suggests that metallic Cu, rich in nanograin boundaries, supports undercoordinated active sites for C–C coupling. Quantitative structure–activity correlation shows that a higher fraction of metallic Cu nanograins leads to higher C 2+ selectivity. A 7 nm Cu nanoparticle ensemble, with a unity fraction of active Cu nanograins, exhibits sixfold higher C 2+ selectivity than the 18 nm counterpart with one-third of active Cu nanograins. The correlation of multimodal operando techniques serves as a powerful platform to advance our fundamental understanding of the complex structural evolution of nanocatalysts under electrochemical conditions. By investigation of structural dynamics during the life cycle of Cu nanocatalysts, correlation of multimodal operando techniques was found to serve as a powerful platform to advance understanding of their complex structural evolution.