Energy articles within Nature Chemistry

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  • Research Briefing |

    Ether-based electrolytes are desired for lithium metal batteries owing to their low reduction potentials; however, they suffer from low anodic stability. Strategic methylation of ether solvents is shown to extend their electrochemical stability and facilitate the formation of LiF-rich interphases, enabling high-voltage lithium metal batteries while avoiding the use of fluorinated solvents.

  • Article |

    Lithium metal batteries are an attractive energy storage technology, but their development relies on the complex interplay between the components’ chemical, physical and mechanical properties. Now, selective methylation of dimethoxyethane ether electrolytes is shown to improve electrolyte, electrode and solid–electrolyte interphase stabilities to enable high-performance 4.3 V lithium metal batteries.

    • Ai-Min Li
    • , Oleg Borodin
    •  & Chunsheng Wang

  • Article |

    Although the light-driven generation of hydrogen from water is a promising approach to renewable fuels, the H–H bond formation step represents a persistent mechanistic question. Now light-harvesting molecular catalysts have been shown to self-assemble into nanoscale aggregates that feature improved efficiency for photoelectrochemical H2 evolution.

    • Isaac N. Cloward
    • , Tianfei Liu
    •  & Alexander J. M. Miller

  • Article |

    Ultra-high-capacity Li–air batteries have low Coulombic efficiency and degrade during re-charging, resulting in a poor cycle life. Redox mediators enable improvements but only at undesirably high potentials. The origin of this high potential and the impact of purported reactive intermediates has now been elucidated by resolving the charging mechanism using Marcus theory.

    • Sunyhik Ahn
    • , Ceren Zor
    •  & Peter G. Bruce

  • News & Views |

    The chemistry of polynitrogens has been enriched by a new isomer of N6 through the synthesis, in a laser-heated diamond anvil cell, of a charged aromatic [N6]4– ring that is recoverable at ambient temperature under high pressure.

    • Sandra Ninet

  • Article |

    Aromatic polynitrogen units can display both high stability and high energy content. A hexazine anion has now been identified in a complex compound, K9N56, which is formed at high pressures and temperatures under laser-heating in a diamond anvil cell. The [N6]4− ring is planar and proposed to be aromatic.

    • Dominique Laniel
    • , Florian Trybel
    •  & Natalia Dubrovinskaia

  • News & Views |

    The adiabatic approximation is often applied to describe the scattering of molecules or atoms from solid surfaces. Now, unusual energy loss has been observed during the scattering of hyperthermal hydrogen atoms from a single crystalline Ge(111) surface — suggesting the existence of a non-adiabatic mechanism involving electronic interband transitions in the Ge that are induced by the hydrogen atoms.

    • Hermann Nienhaus

  • Review Article |

    The light-driven conversion of abundant resources such as CO2 and H2O into chemical fuels for energy storage is crucial to end our dependence on fossil fuels. This Review highlights how molecular catalysts and photosensitizers can be grafted onto metal–organic frameworks to combine the advantages of both classes of compounds. Different synthetic strategies are discussed, along with their advantages and limitations.

    • P. M. Stanley
    • , J. Haimerl
    •  & J. Warnan

  • Perspective |

    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.

    • Mark D. Allendorf
    • , Vitalie Stavila
    •  & Tom Autrey

  • Thesis |

    Bruce Gibb suggests that chemists can play a central role in democratizing access to energy by focusing on common elements.

    • Bruce C. Gibb

  • Article |

    Aqueous organic redox flow batteries offer a safe and inexpensive solution to the problem of storing electricity produced from intermittent renewables. However, decomposition of the redox-active organic molecules that they rely on limits their lifetimes, preventing commercialization. Now it has been shown that these redox molecules can be electro-recomposed in situ, rejuvenating their function.

    • Yan Jing
    • , Evan Wenbo Zhao
    •  & Michael J. Aziz

  • Thesis |

    Bruce C. Gibb offers some suggestions to chemists for how they can help save the world, one nudge at a time.

    • Bruce C. Gibb

  • Article |

    Nickel-rich layered oxides, such as NCM622, are promising cathode materials for lithium batteries, but chemo-mechanical failures hinder their practical application. Now the solid-state synthesis of NCM622 has been studied using multiscale in situ techniques, and kinetic competition between precursor decomposition and lithiation has been observed to lead to spatially heterogeneous intermediates and the formation of defects that are detrimental to cycling.

    • Hyeokjun Park
    • , Hayoung Park
    •  & Kisuk Kang

  • Article |

    The planar hexazine dianion ring (N62–), which had previously been predicted to exist, has now been synthesized from potassium azide (KN3) under laser heating in a diamond anvil cell above 45 GPa; it remains metastable down to 20 GPa. By contrast, at 30 GPa an unusual N2-containing compound with the formula K3(N2)4 was produced.

    • Yu Wang
    • , Maxim Bykov
    •  & Alexander F. Goncharov

  • Article |

    Decoupling the processes of light harvesting and catalytic hydrogen evolution could be a potentially important step in storing solar energy. This has now been achieved with a single molecular unit: a light-harvesting ruthenium complex–polyoxometalate dyad that absorbs light, separates and stores charge and then generates hydrogen on demand following the addition of a proton donor.

    • Sebastian Amthor
    • , Sebastian Knoll
    •  & Carsten Streb

  • Article |

    Super-concentrated water-in-salt electrolytes enable high-voltage aqueous batteries, but have considerable drawbacks such as high viscosity, low conductivity and slow kinetics. Now a concentration-dependent association between CO2 and TFSI– has been discovered and leveraged to decouple the interphasial responsibility of an aqueous electrolyte from its bulk properties, making high-voltage aqueous Li-ion batteries practical in dilute salt-in-water electrolytes.

    • Jinming Yue
    • , Jinkai Zhang
    •  & Liquan Chen

  • Article |

    The use of anionic redox chemistry in high-capacity Li-rich cathodes is being hampered by voltage hysteresis, the origin of which remains obscure. Now it has been shown that sluggish ligand-to-metal charge transfer kinetically traps an intermediate Fe4+ species and is responsible for voltage hysteresis in the prototypical Li-rich cation-disordered rock-salt Li1.17Ti0.33Fe0.5O2.

    • Biao Li
    • , Moulay Tahar Sougrati
    •  & Jean-Marie Tarascon

  • Article |

    Obtaining mechanistic data after the rate-determining step of a chemical reaction is difficult but essential for its understanding. Now, a Ru(iv) side-on peroxo complex has been isolated following the rate-determining step of the water oxidation reaction (O–O bond formation) carried out using a Ru-based molecular catalyst.

    • Carla Casadevall
    • , Vlad Martin-Diaconescu
    •  & Julio Lloret-Fillol

  • Article |

    The overall efficiency of free-triplet generation from intramolecular singlet fission is limited by the efficiency of the dissociation of spatially adjacent triplet pairs. Now, using transient magneto-optical spectroscopy, it has been shown that this limitation can be overcome by promoting a pathway mediated by spatially separated triplet pairs in tetracene trimers and tetramers.

    • Zhiwei Wang
    • , Heyuan Liu
    •  & Min Xiao

  • Article |

    Redox mediators are important for improving the rechargeability of metal–air batteries, however, how they affect singlet oxygen formation and hence parasitic chemistry is unclear, hindering strategies for their improvement. Now, the mechanism of mediated peroxide and superoxide oxidation is elucidated, explaining how redox mediators either enhance or suppress singlet oxygen formation.

    • Yann K. Petit
    • , Eléonore Mourad
    •  & Stefan A. Freunberger

  • Article |

    Moving towards renewable energy sources requires pathways for efficiently converting electricity to chemicals, and gas-fed CO2 electrolysers show promise. Now, the layer-by-layer assembly of a weak-acid cation exchange layer has been shown to affect the local pH in a bipolar-membrane-based gas-fed CO2 electrolyser, improving the conversion efficiency of CO2 to CO by suppressing the competing hydrogen evolution reaction.

    • Zhifei Yan
    • , Jeremy L. Hitt
    •  & Thomas E. Mallouk

  • Article |

    Efficient and stable water oxidation catalysts are important if photoelectrochemical cells are to be used to provide clean and sustainable solar fuels. A water oxidation catalyst that operates at neutral pH has now been developed that features ruthenium coordination oligomers anchored onto the surfaces of graphitic materials through CH–π interactions.

    • Md Asmaul Hoque
    • , Marcos Gil-Sepulcre
    •  & Antoni Llobet

  • Article |

    The strength of electrostatic interactions in semiconductors strongly affects their performance in optoelectronic devices. Now, doping two-dimensional naphthalene-based lead halide perovskites with tetrachloro-1,2-benzoquinone has been shown to introduce donor–acceptor interactions within the organic network, without disrupting the inorganic sublattice. This in turn altered the energy of the materials’ electron–hole electrostatic Coulomb interactions.

    • James V. Passarelli
    • , Catherine M. Mauck
    •  & Samuel I. Stupp

  • Article |

    Singlet fission produces two low-energy triplet excitons that are difficult to dissociate into free charges. Now, separate optima in charge yield have been observed as a function of driving force for singlet and triplet excitons in pentacene. At optimal driving forces, the triplet-exciton dissociation rate is at least five orders of magnitude smaller than the singlet-exciton dissociation rate.

    • Natalie A. Pace
    • , Nadezhda V. Korovina
    •  & Obadiah G. Reid

  • Article |

    The oxidation of water remains the kinetic bottleneck of solar-to-fuel synthesis. Now, spectroelectrochemical evidence together with density functional theory calculations show that charge accumulation determines the reaction mechanism on metal–oxide photoanodes. These insights reveal features that are common to the mechanisms of water oxidation carried out by other inorganic and biological systems.

    • Camilo A. Mesa
    • , Laia Francàs
    •  & James R. Durrant

  • News & Views |

    Interphases that form on the anode surface of lithium-ion batteries are critical for performance and lifetime, but are poorly understood. Now, a decade-old misconception regarding a main component of the interphase has been revealed, which could potentially lead to improved devices.

    • Stefan A. Freunberger

  • Article |

    The solid–electrolyte-interphase layer is extremely important for reversible electrochemical cycling of Li-ion batteries. Now it has been observed that lithium ethylene mono-carbonate, instead of the previously reported lithium ethylene di-carbonate, is the major initial organic species in this layer and it has a high Li-ion conductivity.

    • Luning Wang
    • , Anjali Menakath
    •  & Bryan W. Eichhorn

  • Article |

    Although they are synthetically tunable, organic molecules that undergo singlet fission (the generation of two excitons from one photon) have not demonstrated the excited-state properties necessary to improve optoelectronic devices. Now, a general ‘energy cleft’ molecular design scheme has been demonstrated that enables rapid generation and long lifetimes of multiple triplet excitons that are for device applications.

    • Andrew B. Pun
    • , Amir Asadpoordarvish
    •  & Matthew Y. Sfeir

  • Article |

    The production of ammonia from dinitrogen is a well-studied process; however, the catalytic conversion of ammonia into dinitrogen is underdeveloped. Now, ammonia oxidation has been achieved using ruthenium complexes as catalysts. The production of dinitrogen is observed when ammonium salts are treated with a single-electron oxidant, base and ruthenium catalyst.

    • Kazunari Nakajima
    • , Hiroki Toda
    •  & Yoshiaki Nishibayashi

  • Article |

    Conventional chemical reactors are subject to the equilibrium limitations imposed by the overall reaction. It has now been shown that this limitation can be overcome if reactants are fed separately to a reactor and a non-stoichiometric oxygen carrier is used to transfer both oxygen and key chemical information across a reaction cycle.

    • Ian S. Metcalfe
    • , Brian Ray
    •  & John S. O. Evans

  • Article |

    Developing a stable metallic lithium anode is necessary for next-generation batteries; however, lithium is prone to corrosion, a process that must be better understood if practical devices are to be created. A Kirkendall-type mechanism of lithium corrosion has now been observed. The corrosion is fast and is governed by a galvanic process.

    • Dingchang Lin
    • , Yayuan Liu
    •  & Yi Cui

  • Article |

    The polyoxoanion [P2W18O62]6− has been shown to reversibly accept up to 18 electrons upon reduction in aqueous solution. The resulting highly reduced solution can then be used either for the on-demand generation of hydrogen over a catalyst bed, or as a high-energy-density electrolyte in a redox flow battery.

    • Jia-Jia Chen
    • , Mark D. Symes
    •  & Leroy Cronin

  • Article |

    Calcium-ion batteries are potentially attractive alternatives to lithium-ion batteries, but remain largely unexplored because of low performance. A reversible calcium alloying/de-alloying reaction with the tin anode has now been coupled with the intercalation/de-intercalation of hexafluorophosphate in the graphite cathode to enable a calcium-ion battery that operates stably at room temperature.

    • Meng Wang
    • , Chunlei Jiang
    •  & Hui-Ming Cheng

  • Article |

    Alkali-metal-rich compositions (for example, Li[LixM1–x]O2) are promising battery cathode materials that exhibit oxygen redox, which provides additional charge capacity. It is thought to occur in compounds containing alkali ions in the transition metal layers and featuring Li+–O(2p)–Li+ interactions; however, now it is observed in Na2/3[Mg0.28Mn0.72]O2, in which Mg2+ ions are present in the transition metal layer.

    • Urmimala Maitra
    • , Robert A. House
    •  & Peter G. Bruce

  • News & Views |

    Water-oxidation catalysts that are fast and efficient in strong acid are rare even though there are several benefits for systems working at low pH. Such catalysts usually feature expensive noble metals such as ruthenium and iridum; however, an electrocatalytic system that is exceptionally efficient and based on cobalt has now been developed.

    • Qiushi Yin
    •  & Craig L. Hill

  • News & Views |

    The accumulation of multiple redox equivalents is essential in photo-driven catalytic reactions such as solar water splitting. However, direct spectroscopic observation of a twice-oxidized species under diffuse illumination has proved elusive until now.

    • Anna M. Beiler
    •  & Gary F. Moore

  • Article |

    Photosynthesis uses sunlight to oxidize or reduce reaction centres multiple times and prepare them for multiple-electron-transfer reactions. Now, it has been shown that a molecular proxy for a multiple-electron-transfer electrocatalyst can be oxidized twice by dye molecules when both are anchored to a mesoporous TiO2 thin film and excited with low-intensity visible light.

    • Hsiang-Yun Chen
    •  & Shane Ardo

  • Article |

    Water oxidation is key to the production of chemical fuels from electricity. Now, guided by theory, NiCoFeP oxyhydroxide catalysts have been developed that require an overpotential lower than that required by IrO2. In situ soft X-ray absorption studies of neutral-pH NiCoFeP catalysts indicate formation of Ni4+, which is favourable for water oxidation.

    • Xueli Zheng
    • , Bo Zhang
    •  & Edward H. Sargent

  • Article |

    Electrochemical water oxidation in acidic media is a promising water-splitting technique, but typically requires noble metal catalysts. Now, two polyoxometalate salts based on earth-abundant metals have shown excellent catalytic performance for the oxygen evolution reaction. The barium salt of a cobalt-phosphotungstate polyanion outperformed the state-of-the-art IrO2 catalyst at pHs lower than 1.

    • Marta Blasco-Ahicart
    • , Joaquín Soriano-López
    •  & J. R. Galan-Mascaros

  • Article |

    It is still a great challenge to synthesize value-added products with two or more carbons directly from CO2. Now, a bifunctional catalyst composed of reducible metal oxides (In2O3) and zeolites (HZSM-5) is prepared and yields high selectivity to gasoline-range hydrocarbons (78.6%) with a high octane number directly from CO2 hydrogenation.

    • Peng Gao
    • , Shenggang Li
    •  & Yuhan Sun

  • Article |

    Converting oxygen-rich biomass into fuels requires the removal of oxygen groups through hydrodeoxygenation. MoS2 monolayer sheets decorated with isolated Co atoms bound to sulfur vacancies in the basal plane have now been synthesized that exhibit superior catalytic activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene when compared to conventionally prepared materials.

    • Guoliang Liu
    • , Alex W. Robertson
    •  & Shik Chi Edman Tsang

  • Article |

    The existence of linear scaling relations between the adsorption energies of reaction intermediates on transition-metal surfaces prevents their independent optimization and limits catalytic activity. It has now been shown that using a catalytic LiH site alongside a transition-metal catalyst can break these intrinsic scaling relations, leading to unprecedented lower-temperature ammonia-synthesis activity.

    • Peikun Wang
    • , Fei Chang
    •  & Ping Chen

  • News & Views |

    The slow kinetics of light-driven water oxidation on haematite is an important factor limiting the material's efficiency. Now, an intermediate of the water-splitting reaction has been identified offering hope that the full mechanism will soon be resolved.

    • Alexander J. Cowan

  • Article |

    [NiFe] hydrogenases are enzymes containing nickel and iron centres that catalyse hydrogen evolution with performances that rival those of platinum catalysts. Now, a NiFe model complex has been reported that mimics the structure and the Ni-centred hydrogen evolution activity found at the active site of [NiFe] hydrogenases.

    • Deborah Brazzolotto
    • , Marcello Gennari
    •  & Carole Duboc

  • Article |

    Photoelectrochemical water oxidation with haematite is known to be associated with a build-up of holes at the electrode surface. Infrared spectra acquired during photoelectrochemical water oxidation have now allowed these holes to be identified as high-valent iron–oxo intermediate species involved in the water oxidation reaction.

    • Omid Zandi
    •  & Thomas W. Hamann

  • Article |

    While important for solar energy conversion, it is unclear whether electron transfer at molecular–semiconductor interfaces is influenced only by the distance over which the injected electron tunnels and whether specific through-bond pathways are active. Now, a pathway for electron transfer has been identified through comparative analysis of compounds with phenyl- or xylyl-thiophene bridges.

    • Ke Hu
    • , Amber D. Blair
    •  & Curtis P. Berlinguette

  • Article |

    A primary objective in solar energy conversion is to achieve long-lived light-driven redox separation. Now a modular self-assembly strategy has been developed to construct molecular p/n junctions surface-bound to transparent conducting ITO nanoparticle electrodes. Both photoanode and photocathode assemblies achieved remarkably long-lived redox separation lifetimes without making use of traditional wide-bandgap semiconductors.

    • Byron H. Farnum
    • , Kyung-Ryang Wee
    •  & Thomas J. Meyer

  • Article |

    The chemistry of the transition metals within the oxide cathodes of lithium-ion batteries typically limits their capacity, however, reversible oxygen redox could potentially break this limit. It is now demonstrated that Li-excess and cation disorder create specific environments around oxygen atoms that lead to labile oxygen electrons that participate in the practical capacity of cathodes.

    • Dong-Hwa Seo
    • , Jinhyuk Lee
    •  & Gerbrand Ceder

  • Article |

    Designing improved catalysts is predicated on understanding how they work. Now, by positioning three ruthenium centres in a macrocyclic framework, a remarkable acceleration of catalytic water oxidation has been achieved. Detailed mechanistic studies revealed that the catalyst operates through the ‘water nucleophilic attack’ pathway—similar to the natural oxygen-evolving cluster of photosystem II.

    • Marcus Schulze
    • , Valentin Kunz
    •  & Frank Würthner

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