Dinitrogen reduction to ammonia using transition metal catalysts is central to both the chemical industry and the Earth's nitrogen cycle. In the Haber–Bosch process, a metallic iron catalyst and high ...temperatures (400 °C) and pressures (200 atm) are necessary to activate and cleave NN bonds, motivating the search for alternative catalysts that can transform N2 to NH3 under far milder reaction conditions. Here, the successful hydrothermal synthesis of ultrathin TiO2 nanosheets with an abundance of oxygen vacancies and intrinsic compressive strain, achieved through a facile copper‐doping strategy, is reported. These defect‐rich ultrathin anatase nanosheets exhibit remarkable and stable performance for photocatalytic reduction of N2 to NH3 in water, exhibiting photoactivity up to 700 nm. The oxygen vacancies and strain effect allow strong chemisorption and activation of molecular N2 and water, resulting in unusually high rates of NH3 evolution under visible‐light irradiation. Therefore, this study offers a promising and sustainable route for the fixation of atmospheric N2 using solar energy.
Ultrathin TiO2 nanosheets with abundant oxygen vacancies (VO) are synthesized through a facile copper‐doping strategy, exhibiting remarkable and stable performance for the photofixation of N2 to NH3 at a rate of 78.9 µmol g−1 h−1 under ambient conditions (especially up to 700 nm). The outstanding activity can be attributed to the existence of VO and compressive strain in the nanosheets.
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Abstract
Oxygen evolution reaction catalysts capable of working efficiently in acidic media are highly demanded for the commercialization of proton exchange membrane water electrolysis. Herein, we ...report a Zn-doped RuO
2
nanowire array electrocatalyst with outstanding catalytic performance for the oxygen evolution reaction under acidic conditions. Overpotentials as low as 173, 304, and 373 mV are achieved at 10, 500, and 1000 mA cm
−2
, respectively, with robust stability reaching to 1000 h at 10 mA cm
−2
. Experimental and theoretical investigations establish a clear synergistic effect of Zn dopants and oxygen vacancies on regulating the binding configurations of oxygenated adsorbates on the active centers, which then enables an alternative Ru−Zn dual-site oxide path of the reaction. Due to the change of reaction pathways, the energy barrier of rate-determining step is reduced, and the over-oxidation of Ru active sites is alleviated. As a result, the catalytic activity and stability are significantly enhanced.
A series of novel CoFe‐based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered‐double‐hydroxide (LDH) nanosheets at 300–700 °C. The chemical composition and morphology of ...the reaction products (denoted herein as CoFe‐x) are highly dependent on the reduction temperature (x). CO2 hydrogenation experiments are conducted on the CoFe‐x catalysts under UV–vis excitation. With increasing LDH‐nanosheet reduction temperature, the CoFe‐x catalysts show a progressive selectivity shift from CO to CH4, and eventually to high‐value hydrocarbons (C2+). CoFe‐650 shows remarkable selectivity toward hydrocarbons (60% CH4, 35% C2+). X‐ray absorption fine structure, high‐resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina‐supported CoFe‐alloy nanoparticles are responsible for the high selectivity of CoFe‐650 for C2+ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar‐energy to produce valuable chemicals and fuels from CO2.
Three unique CoFe‐based catalysts are successfully fabricated via direct H2 reduction of a CoFeAl layered‐double‐hydroxide (CoFeAl‐LDH) nanosheets precursor by varying the reduction temperature. LDH precursor reduction at temperatures above 600 °C results in the formation of CoFe‐alloy nanoparticles, thereby affording a remarkable CO2 hydrogenation selectivity toward high‐value (C2+) hydrocarbons under simulated solar excitation through photothermal effects.
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Cu2O, a low‐cost, visible light responsive semiconductor photocatalyst represents an ideal candidate for visible light driven photocatalytic reduction of N2 to NH3 from the viewpoint of ...thermodynamics, but it remains unexplored. Reported here is the successful synthesis of uniformly sized and ultrafine Cu2O platelets, with a lateral size of <3 nm, by the in situ topotactic reduction of a CuII‐containing layered double hydroxide with ascorbic acid. The supported ultrafine Cu2O offered excellent performance and stability for the visible light driven photocatalytic reduction of N2 to NH3 (the Cu2O‐mass‐normalized rate as high as 4.10 mmol gCu2O
−1 h−1 at λ>400 nm), with the origin of the high activity being long‐lived photoexcited electrons in trap states, an abundance of exposed active sites, and the underlying support structure. This work guides the future design of ultrafine catalysts for NH3 synthesis and other applications.
Ultrafine Cu2O, less than 3 nm in size, was synthesized by facile in situ reduction of layered double hydroxide (LDH). This ultrafine Cu2O exhibits superior performance for visible light driven N2 reduction to NH3, with a nearly 64‐fold increase in NH3 production rate compared to bulk Cu2O, and it is superior to most of the reported benchmark photocatalysts. The remarkable activity can be attributed to the availability of surface sites and the generation of long‐lived photoexcited electrons.
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Developing a reliable strategy for the modulation of the texture, composition, and electronic structure of electrocatalyst surfaces is crucial for electrocatalytic performance, yet still challenging. ...Herein, we develop a facile and universal strategy, quenching, to precisely tailor the surface chemistry of metal oxide nanocatalysts by rapidly cooling them in a salt solution. Taking NiMoO4 nanocatalysts an example, we successfully produce the quenched nanocatalysts offering a greatly reduced oxygen evolution reaction (OER) overpotential by 85 mV and 135 mV at 10 mA cm–2 and 100 mA cm–2 respectively. Through detailed characterization studies, we establish that quenching induces the formation of numerous disordered stepped surfaces and the near-surface metal ions doping, thus regulating the local electronic structures and coordination environments of Ni, Mo, which promotes the formation of the dual-site active and thereby affords a low energy pathway for OER. This quenching strategy is also successfully applied to a number of other metal oxides, such as spinel-type Co3O4, Fe2O3, LaMnO3, and CoSnO3, with similar surface modifications and gains in OER activity. Our finding provides a new inspiration to activate metal oxide catalysts and extends the use of quenching chemistry in catalysis.
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Ni3FeN nanoparticles with a particle size of ≈100 nm and a thickness of ≈9 nm are successfully synthesized by thermal ammonolysis of ultrathin NiFe‐layered double hydroxide ultrathin nanosheets. The ...Ni3FeN nanoparticles exhibit excellent catalytic performance and high stability in electrochemical overall water splitting.
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Uranium extraction from seawater provides an opportunity for sustainable fuel supply to nuclear power plants. Herein, an adsorption–electrocatalysis strategy is demonstrated for efficient uranium ...extraction from seawater using a functionalized iron–nitrogen–carbon (Fe–Nx–C–R) catalyst, comprising N‐doped carbon capsules supporting FeNx single‐atom sites and surface chelating amidoxime groups (R). The amidoxime groups bring hydrophilicity to the adsorbent and offer surface‐specific binding sites for UO22+ capture. The site‐isolated FeNx centres reduce adsorbed UO22+ to UO2+. Subsequently, through electrochemical reduction of the FeNx sites, unstable U(V) ions are reoxidized to U(VI) in the presence of Na+ resulting in the generation of solid Na2O(UO3·H2O)x, which can easily be collected. Fe–Nx–C–R reduced the uranium concentration in seawater from ≈3.5 ppb to below 0.5 ppb with a calculated capacity of ≈1.2 mg g‐1 within 24 h. To the best of the knowledge, the developed system is the first to use the adsorption of uranyl ions and electrodeposition of solid Na2O(UO3.H2O)x for the extraction of uranium from seawater. The important discoveries guide technology development for the efficient extraction of uranium from seawater.
A novel adsorption–electrocatalysis system is developed for efficiently extracting uranium from seawater. Amidoxime groups impart Fe–Nx–C–R with hydrophilicity and a high binding affinity for uranyl ions, whilst the iron sites provides a reversible electron‐transfer platform for the eventual production of Na2O(UO3·H2O)x in the presence of Na+, thus allowing facile uranium recovery and Fe–Nx–C–R reuse.
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The solar‐driven conversion of CO2 into carbon‐based fuels and other valuable chemical feedstocks is actively being pursued as an approach for curbing greenhouse gas emissions. Herein, a series of ...novel Fe‐based catalysts with different chemical compositions are successfully fabricated through the hydrogen reduction of MgFeAl‐layered double hydroxide nanosheets at temperatures from 300 to 700 °C. The catalysts obtained are denoted herein as Fe‐x, where x is the reduction temperature in celsius. Fe‐500 offers outstanding activity for the photothermal conversion of CO2 to C2+ hydrocarbons under ultraviolet‐visible (UV‐Vis) irradiation (CO2 conversion 50.1%, C2+ selectivity 52.9%). Characterization studies using X‐ray diffraction, extended X‐ray absorption fine structure, Mössbauer spectroscopy, and high‐resolution transmission electron microscopy determine that the Fe‐500 catalyst is comprised of Fe and FeOx nanoparticles on a MgO–Al2O3 mixed metal oxide support. Density functional theory calculations establish that heterostructures consisting of partially oxidized metallic Fe nanoparticles improve the CC coupling ability of CO2 hydrogenation intermediates, thus enhancing the selectivity to C2+ products. This work introduces a novel photothermal hydrogenation strategy for converting CO2 into valuable chemicals and also opens new avenues toward the development of related solar energy utilization schemes.
A series of Fe‐containing catalysts (denoted herein as Fe‐x) are successfully synthesized by partial H2 reduction of a MgFeAl‐layered double hydroxide nanosheet precursor at different temperatures (x) in the range 300–700 °C. The Fe‐500 catalyst, comprised of Fe0/FeOx nanoparticles on a MgO‐Al2O3 support, displays outstanding photothermal performance for CO2 hydrogenation to C2+ hydrocarbons under ultraviolet‐visible (UV‐Vis) irradiation.
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This study reports the synthesis of ultrafine NiFe‐layered double hydroxide (NiFe‐LDH) nanosheets, possessing a size range between 1.5 and 3.0 nm with a thickness of 0.6 nm. Abundant metal and oxygen ...vacancies impart the ultrafine nanosheets with semi‐metallic character, and thus superior charge transfer properties and electrochemical water oxidation performance with overpotentials (η) of 254 mV relative to monolayer LDH nanosheets (η of 280 mV) or bulk LDH materials (η of 320 mV) at 10 mA cm−2. These results are highly encouraging for the future application of ultrafine monolayer LDH nanosheets in electronics, solar cells, and catalysis.
Ultrafine monolayer layered double hydroxide (LDH) nanosheets with a mean lateral size of less than 3 nm are obtained by the ultrasonic treatment of monolayer LDH nanosheets. Abundant vacancies impart the ultrafine nanosheets with semi‐metallic character, superior charge transfer properties, and electrocatalytic oxygen evolution performance relative to monolayer LDH nanosheets.
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