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Space charge governs the kinetics of metal exsolution
The self-assembly of metallic nanoparticles on oxide supports via metal exsolution relies on dopant transport, but strong electrostatic gradients and space charges typically control the properties of surfaces. The surface–dopant interaction is shown to be the main determining factor for the exsolution kinetics of nickel in a perovskite system.
- Moritz L. Weber
- , Břetislav Šmíd
- & Christian Lenser
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Article |
Defect-driven anomalous transport in fast-ion conducting solid electrolytes
Solid-state ionic conduction is a key enabler of electrochemical energy storage and conversion. A quantitative framework for ionic conduction between atomistic and macroscopic timescales in β- and β″-aluminas is now proposed for ‘atoms-to-device’ multiscale modelling and optimization.
- Andrey D. Poletayev
- , James A. Dawson
- & Aaron M. Lindenberg
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News & Views |
Enabling low-cost and sustainable fuel cells
A hydroxide exchange membrane fuel cell consisting of a nickel-based anode and a cobalt–manganese–oxide cathode is shown to achieve a power density of 488 mW cm–2 at 95 °C.
- Frédéric Jaouen
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Article |
An efficient nickel hydrogen oxidation catalyst for hydroxide exchange membrane fuel cells
Hydroxide exchange membrane fuel cells are promising as an energy conversion technology, but require platinum group metal electrocatalysts for their application. A Ni-based hydrogen oxidation reaction catalyst is now shown to exhibit unprecedented electrochemical performance.
- Weiyan Ni
- , Teng Wang
- & Xile Hu
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Article |
Chemical vapour deposition of Fe–N–C oxygen reduction catalysts with full utilization of dense Fe–N4 sites
Replacing platinum with metal–nitrogen–carbon catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells has been impeded by low activity. These limitations have now been overcome by the trans-metalation of Zn–N4 sites into Fe–N4 sites.
- Li Jiao
- , Jingkun Li
- & Qingying Jia
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Review Article |
Triple ionic–electronic conducting oxides for next-generation electrochemical devices
Triple ionic–electronic conductors can be used in electrochemical devices, including fuel cells, membrane reactors and electrolysis cells. Current understanding in single-phase conductors including defect formation and conduction mechanisms are now discussed.
- Meagan Papac
- , Vladan Stevanović
- & Ryan O’Hayre
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Article |
Synergistically integrated phosphonated poly(pentafluorostyrene) for fuel cells
Phosphonated polymers have been proposed as anhydrous proton conductors for fuel cells but anhydride formation of phosphonic acid functional groups lowers conductivity. A synergistically integrated phosphonated poly(pentafluorostyrene) is shown to maintain high protonic conductivity above 200 °C.
- Vladimir Atanasov
- , Albert S. Lee
- & Yu Seung Kim
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Article |
Self-supported Pt–CoO networks combining high specific activity with high surface area for oxygen reduction
A high oxygen reduction reaction activity can usually be realized by increasing platinum specific activity at the expense of active surface area. Self-supported platinum–cobalt-oxide networks combining high activity and surface area now promise a stable fuel-cell operation.
- Gustav W. Sievers
- , Anders W. Jensen
- & Matthias Arenz
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Article |
Eliminating dissolution of platinum-based electrocatalysts at the atomic scale
Deployment of proton-exchange membrane fuel cells is limited by the durability of Pt-nanoscale catalysts during cathodic oxygen reduction reactions. Dissolution processes on single crystalline and thin film surfaces are now correlated leading to the design of PtAu catalysts with suppressed dissolution.
- Pietro P. Lopes
- , Dongguo Li
- & Vojislav R. Stamenkovic
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Article |
P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction
For oxygen reduction and hydrogen oxidation reactions, proton-exchange membrane fuel cells typically rely on precious-metal-based catalysts. A p-block single-metal-site tin/nitrogen-doped carbon is shown to exhibit promising electrocatalytic and fuel cell performance.
- Fang Luo
- , Aaron Roy
- & Peter Strasser
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Article |
High oxide ion and proton conductivity in a disordered hexagonal perovskite
Fast oxide ion and proton conductors at intermediate temperature are required to improve the performance of ceramic fuel cells. An undoped hexagonal perovskite Ba7Nb4MoO20 electrolyte with high proton and oxide ion conductivity (4.0 mS cm−1) at 510 °C is now reported.
- Sacha Fop
- , Kirstie S. McCombie
- & Abbie C. Mclaughlin
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Article |
Nanoscale percolation in doped BaZrO3 for high proton mobility
Although acceptor-doped barium zirconate is a promising conductor for electrolysers or fuel cells, our understanding of the relationship between proton motion and conductivity is limited. Our simulations now suggest a generic nanoscale percolation mechanism for high mobility in other oxides.
- Fabian M. Draber
- , Christiane Ader
- & Manfred Martin
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Letter |
Engineering stable electrocatalysts by synergistic stabilization between carbide cores and Pt shells
Using core–shell particles represents an effective design strategy for improving the performance of noble metal catalysts, but their stabilities can suffer during reactions. Atomically thin Pt shells are shown to stabilize titanium tungsten carbide cores, even at highly oxidizing potentials.
- Daniel Göhl
- , Aaron Garg
- & Marc Ledendecker
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Article |
Hydrophilic microporous membranes for selective ion separation and flow-battery energy storage
Ion-selective membranes are widely used for water purification and electrochemical energy devices but designing their pore architectures is challenging. Membranes with narrow channels and hydrophilic functionality are shown to exhibit salt ions transport and selectivity towards small organic molecules.
- Rui Tan
- , Anqi Wang
- & Qilei Song
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Article |
Mixed proton and electron conducting double perovskite anodes for stable and efficient tubular proton ceramic electrolysers
Proton ceramic electrolysers can produce hydrogen directly from steam, but their development has suffered from limited electrical efficiency. A fully operational and stable BaZrO3-based tubular electrolyser with high hydrogen production rate is now reported.
- Einar Vøllestad
- , Ragnar Strandbakke
- & Truls Norby
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Article |
Interplay of water and reactive elements in oxidation of alumina-forming alloys
The crucial interaction between reactive elements and water vapour during the oxide scale growth of alumina-forming alloys is revealed, providing insights to improve corrosion resistance of high-temperature alloys.
- N. Mortazavi
- , C. Geers
- & L. G. Johansson
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Article |
Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures
Designing stable mechanical actuators and sensors for applications in extreme environments is difficult. A high-temperature and low-voltage electromechanical oxide actuator based on PrxCe1−xO2−δ and exhibiting dynamic chemical expansion is now reported.
- Jessica G. Swallow
- , Jae Jin Kim
- & Krystyn J. Van Vliet
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Article |
Real-time impedance monitoring of oxygen reduction during surface modification of thin film cathodes
Cathodes with enhanced catalytic activity for oxygen reduction are needed for solid oxide fuel cells. Although perovskite-type oxides typically suffer from performance degradation, high surface activity is now shown to be related to a few active sites.
- Ghislain M. Rupp
- , Alexander K. Opitz
- & Jürgen Fleig
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Review Article |
Energy and fuels from electrochemical interfaces
Advances in electrocatalysis at interfaces are vital for driving technological innovations related to energy. New materials developments for efficient hydrogen and oxygen production in electrolysers and in fuel cells are described.
- Vojislav R. Stamenkovic
- , Dusan Strmcnik
- & Nenad M. Markovic
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Article |
Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface
The chemical instability of perovskite oxide surfaces limits their energy conversion performance. Significantly enhanced electrochemical stability in a model perovskite electrocatalyst has now been achieved using less reducible cations.
- Nikolai Tsvetkov
- , Qiyang Lu
- & Bilge Yildiz
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Letter |
Probing disorder in isometric pyrochlore and related complex oxides
Disordering in complex oxides is important for their radiation resistance. It is now shown that pyrochlores disorder by the formation of a weberite-like phase, with similar behaviour observed in spinels, adding complexity to their disordering.
- Jacob Shamblin
- , Mikhail Feygenson
- & Maik Lang
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Article |
Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials
Although Fe–N–C materials are promising catalysts for oxygen electroreduction in polymer fuel cells, the structure of their active sites is unclear. Quantitative analysis of Fe–N–C now reveals the existence of porphyrin-like FeN4C12 moieties.
- Andrea Zitolo
- , Vincent Goellner
- & Frédéric Jaouen
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Article |
The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes
Manipulating strain states to modulate ionic conduction in micro energy devices has proved difficult. Effective net strain is now used to control oxygen ionic transport kinetics in ceria-based electrolyte membranes.
- Yanuo Shi
- , Alexander Hansen Bork
- & Jennifer Lilia Marguerite Rupp
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Article |
Eliminating degradation in solid oxide electrochemical cells by reversible operation
Although solid oxide electrochemical cells can store electricity and convert fuels to electricity, their development is limited by long-term stability. Degradation is now eliminated by reversibly cycling between electrolysis and fuel-cell modes.
- Christopher Graves
- , Sune Dalgaard Ebbesen
- & Mogens Bjerg Mogensen
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Letter |
Layered oxygen-deficient double perovskite as an efficient and stable anode for direct hydrocarbon solid oxide fuel cells
Layered double perovskites are promising as solid oxide fuel cell electrodes because of favourable transport properties. Related layered materials are now used as high-performance anodes that exhibit redox stability when exposed to hydrocarbon fuels.
- Sivaprakash Sengodan
- , Sihyuk Choi
- & Guntae Kim
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Article |
High H− ionic conductivity in barium hydride
Heavy alkaline-earth hydrides could be of interest as ionically conducting electrolytes for electrochemical applications. Barium hydride is now shown to exhibit fast ionic transport of hydride ions in a high-temperature and high-symmetry phase.
- Maarten C. Verbraeken
- , Chaksum Cheung
- & John T. S. Irvine
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Letter |
A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3
Oxide ion conductors are technologically relevant for applications in electrochemical devices such as sensors, separation membranes and fuel cells. Magnesium doping in Na0.5Bi0.5TiO3—a piezoelectric material that suffers from high leakage conductivity—now results in a family of ionic conductors that could prove significant not only for dielectric-based applications but also for intermediate-temperature solid-oxide fuel cells.
- Ming Li
- , Martha J. Pietrowski
- & Derek C. Sinclair
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Article |
Proton trapping in yttrium-doped barium zirconate
Although high proton conductivity and chemical stability in yttrium-doped barium zirconate are of interest for intermediate-temperature solid-oxide fuel cells, there are remaining issues regarding its defect chemistry and macroscopic proton-transport mechanism. Proton transport in this compound is shown to be limited by proton–dopant association, and the presence of two types of proton environment above room temperature are observed, reflecting differences in proton–dopant configurations.
- Yoshihiro Yamazaki
- , Frédéric Blanc
- & Sossina M. Haile
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Article |
Probing oxygen vacancy concentration and homogeneity in solid-oxide fuel-cell cathode materials on the subunit-cell level
Although oxygen vacancy distributions and dynamics control the operation of solid-oxide fuel cells, understanding the atomistic mechanisms involved during operation of the cell has proved difficult. An approach for the direct mapping of oxygen vacancy concentrations based on local lattice parameter measurements by scanning transmission electron microscopy is now proposed.
- Young-Min Kim
- , Jun He
- & Albina Y. Borisevich
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Article |
High electrochemical activity of the oxide phase in model ceria–Pt and ceria–Ni composite anodes
A key step in fuel-cell energy-conversion processes is electro-oxidation of the fuel at the anode, but ways to improve electrocatalytic activity remain unclear. Using ceria–metal structures, H2-oxidation reactions are shown to be dominated by electrocatalysis at the oxide/gas interface with minimal contributions from the oxide/metal/gas triple-phase boundaries.
- William C. Chueh
- , Yong Hao
- & Sossina M. Haile
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Article |
Co3O4 nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction
Developing oxygen-electrode catalysts with high activity at low cost for renewable energy applications such as water splitting and fuel cells is challenging. A hybrid material of Co3O4 nanocrystals grown on reduced graphene oxide exhibits enhanced catalytic performance for the oxygen reduction and oxygen evolution reactions.
- Yongye Liang
- , Yanguang Li
- & Hongjie Dai
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Letter |
Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules
Cathode degradation and methods for improving the selectivity of anode catalysts remain crucial challenges for the design of polymer electrolyte membrane fuel cells. A chemically modified Pt electrode with a self-assembled monolayer of calix[4]arene molecules is now shown to selectively block the undesired oxygen reduction reaction.
- Bostjan Genorio
- , Dusan Strmcnik
- & Nenad M. Marković
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Article |
Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy
In situ spectroscopic analysis of operating solid oxide electrochemical cells has proved to be difficult owing to high-vacuum requirements. Ambient-pressure X-ray photoelectron spectroscopy on single-chamber cells now suggests that surface reaction kinetics and electron transport on the electrodes are co-limiting processes.
- Chunjuan Zhang
- , Michael E. Grass
- & Bryan W. Eichhorn
Metal bond strength regulation enables large-scale synthesis of intermetallic nanocrystals for practical fuel cells
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