Publications
332 results found
Westhead O, Spry M, Bagger A, et al., 2023, The role of ion solvation in lithium mediated nitrogen reduction, Journal of Materials Chemistry A, ISSN: 2050-7488
Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of −2 mA cm−2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.
Hongrutai N, Nganglumpoon R, Watmanee S, et al., 2023, In-situ electrodeposited Ag/Cu for electrochemical reduction of acetic acid to nanodiamond under ambient conditions, Materials Today Chemistry, Vol: 30
Carbon nanostructured materials such as nanodiamonds and graphene are useful for various applications, but their low-energy production technologies remain an important challenge to overcome. Herein, the electrochemical reduction of acetic acid using in-situ electrodeposited Ag/Cu to nanocrystalline carbon products was investigated as a function of AgNO3 concentrations in the presence of water and [BMIM]+[BF4]- ionic liquid. Under the conditions used, the deposited Ag clusters could become negatively charged and were responsible for the reduction of acetic acid and the consequent crystalline carbon growth. Increasing Ag concentrations did not only result in higher amounts of Ag being deposited but also created significant local pressure on the atomistic level, where the crystalline carbon was formed, resulting in the re-ordering of carbon atoms into nanodiamond structure. The presence of nanodiamond with average crystallite size 27 nm was clearly evidenced by XRD, Raman, XPS, and TEM-EDX-SAED. The in-situ electrochemical reduction has shown to be an effective ultra-low energy strategy to produce crystalline solid carbon under ambient conditions.
Liang X, Wang S, Feng J, et al., 2023, Structural transformation of metal-organic frameworks and identification of electrocatalytically active species during the oxygen evolution reaction under neutral conditions, Inorganic Chemistry Frontiers, Vol: 10, Pages: 2961-2977
The electrocatalytic oxygen evolution reaction (OER) under neutral or near-neutral conditions has attracted research interest due to its environmental friendliness and economic sustainability in comparison with currently available acidic and alkaline conditions. However, it is challenging to identify electrocatalytically active species in the OER procedure under neutral environments due to non-crystalline forms of catalysts. Crystalline metal-organic framework (MOF) materials could provide novel insights into electrocatalytically active species because of their well-defined structures. In this study, we synthesized two isostructural two-dimensional (2D) MOFs [Co(HCi)2(H2O)2·2DMF]n (Co-Ci-2D) and [Ni(HCi)2(H2O)2·2DMF]n (Ni-Ci-2D) (H2Ci = 1H-indazole-5-carboxylic acid, DMF = N,N-dimethyl-formamide) to investigate their OER performance in a neutral environment. Our results indicate that Co-Ci-2D holds a current density of 3.93 mA cm−2 at 1.8 V vs. RHE and an OER durability superior to the benchmark catalyst IrO2. Utilizing the advantages of the structural transformation of MOF materials which are easier to characterize and analyze compared with ill-defined amorphous materials, we found that a mononuclear coordination compound [Co(HCi)2(H2O)4] (Co-Ci-mono-A) and its isomer (Co-Ci-mono-B) were proved to be active species of Co-Ci-2D in the neutral OER process. For Ni-Ci-2D, mononuclear coordination compounds similar to the structures of the cobalt material (Ni-Ci-mono-A and Ni-Ci-mono-B) together with NiHPO4 formed by the precipitation were confirmed as active species for neutral OER catalysis. Additionally, the difference in OER activities between Co-Ci-2D and Ni-Ci-2D, approximately one order of magnitude, can be attributed to changes in bond strength resulting from variations in bond length within coordination octahedra after being treated with the PBS solution. These findings contribute to a better comprehension of the OER procedure in neutral med
de Tomas C, Alabidun S, Chater L, et al., 2023, Doping carbon electrodes with sulfur achieves reversible sodium ion storage, JPhys Energy, Vol: 5
We present a combination of experiments and theory to study the effect of sulfur doping in hard carbons anodes for sodium-ion batteries. Hard carbons are synthesised through a two step process: hydrothermal carbonisation followed by pyrolysis of a biomass-derived carbon precursor. Subsequent sulfur doping is introduced via chemical-vapour deposition. The resulting sulfur-doped hard carbon shows enhanced sodium storage capacity with respect to the pristine material, with significantly improved cycling reversibility. Atomistic first principles simulations give insight into this behaviour, revealing that sulfur chemisorbed onto the hard carbon increases the sodium adsorption energies and facilitates sodium desorption. This mechanism would increase reversible Na storage, confirming our experimental observations and opening a pathway towards more efficient Na-ion batteries.
Li F, Guo Z, Song Z, et al., 2023, Ultrafast synthesis of battery grade graphite enabled by a multi-physics field carbonization, Chemical Engineering Journal, Vol: 461, ISSN: 1385-8947
The typical synthesis of graphite requires carbonization at 2800 °C, which consumes a substantial amount of energy. We present a novel, sustainable and cost-effective method for synthesizing high-crystallinity graphite in 13 min at a low temperature of 1100 °C and a multi-physics field (MPF) carbonization coupling with a Ni catalyst. The MPF synergistically benefits from a thermal field, an electric field, and a pressure field in an MPF furnace at the lab scale. Molecular dynamics and differential charge density calculation indicated that the MPF carbonization facilitated exceptional kinetics, and considerably accelerated the breaking of the Ni-metal-catalyzed C-O bonds. The starch-derived graphite anode provided a reversible Li+ storage capacity of 370.7 mAh g−1, matching that of commercial graphite. It also demonstrates exceptional rate performance with a capacity of 103.3 mAh g−1 at an ultra-high current density of 30 A g−1 in diglyme-based Na-ion batteries and ultrastable cycling performance over 10,000 cycles at 2 A g−1. This method will shed some light on how to rapidly fabricate highly crystalline graphite by a energy-saving and low-cost route.
Xu Y, Titirici M, Chen J, et al., 2023, 2023 roadmap for potassium-ion batteries, JOURNAL OF PHYSICS-ENERGY, Vol: 5, ISSN: 2515-7655
Madhu R, Periasamy AP, Schlee P, et al., 2023, Lignin: A sustainable precursor for nanostructured carbon materials for supercapacitors, Carbon, Vol: 207, Pages: 172-197, ISSN: 0008-6223
After being undervalued for a long-time, the potential use of lignins have gained interest as a source of wealth from waste. Despite the complexity of lignins chemical structure, its high carbon content compared to cellulose and sugars makes lignin a very promising precursor for the development of nanocarbons for broad range applications, including supercapacitors for energy storage. High performing supercapacitors have been made using dimensionally different nanocarbon entities (zero-to three), such as carbon nanoparticles, carbon nanodots, carbon fibers, and carbon nanosheets with modular and interconnected pore structures, which are prepared from lignins of various types with and without use of templates, porogens and chemical agents. Control of physicochemical and electrochemical properties in such nanocarbons remains the key for their high energy density, flexibility, and long-term stability. To this end, nanocarbons conductivity, porosity and surface areas are controlled by various synthesis approaches while detailed adjustment of pore structure, pore width and pore distribution have been made to improve electrolyte access, ions confinement, and transportation. To compare performances of nanocarbons made from different lignin types, we must do meaningful investigations on the lignin's structure, composition, and purity to understand how their structure-property relationships are influenced by pyrolysis, carbonization and activation methods/conditions used. In this review, a clear overview of the lignins structure, classification, and properties is presented, wherein we compared the structure-property-performance relationships of nanostructured carbons from lignins for improvement of supercapacitor device performances with recent advances.
Xie H, Xie R, Zhang Z, et al., 2023, Achieving highly selective electrochemical CO<inf>2</inf> reduction to C<inf>2</inf>H<inf>4</inf> on Cu nanosheets, Journal of Energy Chemistry, Vol: 79, Pages: 312-320, ISSN: 2095-4956
The conversion of CO2 into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive. CuO nanosheets with an average size and thickness of ∼ 30 and ∼ 20 nm have been developed, which are in situ reduced into Cu nanosheets during electrochemical CO2 reduction reaction (ECO2RR). The derived Cu nanosheets demonstrate much higher selectivity for C2H4 production than commercial CuO derived Cu powder, with an optimum Faradaic efficiency of 56.2% and a partial current density of C2H4 as large as 171.0 mA cm−2 in a gas diffusion flow cell. The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5 (4–6), which facilitates the formation of *CHO rather than *COH intermediate, meanwhile boosting the C [sbnd] C coupling reaction of *CO and *CHO intermediates, which are the critical steps for C2H4 formation.
Barrio J, Pedersen A, Sarma SC, et al., 2023, FeNC Oxygen Reduction Electrocatalyst with High Utilization Penta-Coordinated Sites., Adv Mater, Vol: 35
Atomic Fe in N-doped carbon (FeNC) electrocatalysts for oxygen (O2 ) reduction at the cathode of proton exchange membrane fuel cells are the most promising alternative to platinum-group-metal catalysts. Despite recent progress on atomic FeNC O2 reduction, their controlled synthesis and stability for practical applications remain challenging. A two-step synthesis approach has recently led to significant advances in terms of Fe-loading and mass activity; however, the Fe utilization remains low owing to the difficulty of building scaffolds with sufficient porosity that electrochemically exposes the active sites. Herein, this issue is addressed by coordinating Fe in a highly porous nitrogen-doped carbon support (≈3295 m2 g-1 ), prepared by pyrolysis of inexpensive 2,4,6-triaminopyrimidine and a Mg2+ salt active site template and porogen. Upon Fe coordination, a high electrochemical active site density of 2.54 × 1019 sites gFeNC -1 and a record 52% FeNx electrochemical utilization based on in situ nitrite stripping are achieved. The Fe single atoms are characterized pre- and post-electrochemical accelerated stress testing by aberration-corrected high-angle annular dark field scanning transmission electron microscopy, showing no Fe clustering. Moreover, ex situ X-ray absorption spectroscopy and low-temperature Mössbauer spectroscopy suggest the presence of penta-coordinated Fe sites, which are further studied by density functional theory calculations.
Baragau IA, Buckeridge J, Nguyen KG, et al., 2023, Outstanding visible light photocatalysis using nano-TiO<inf>2</inf> hybrids with nitrogen-doped carbon quantum dots and/or reduced graphene oxide, Journal of Materials Chemistry A, Vol: 11, Pages: 9791-9806, ISSN: 2050-7488
Historically, titanium dioxide (TiO2) has been one of the most extensively studied metal oxide photocatalysts; however, it suffers from a large bandgap and fast charge recombination. We report the use of green, rapid, single-step continuous hydrothermal flow synthesis for the preparation of TiO2, and TiO2 hybrids with reduced graphene oxide (rGO) and/or N-doped carbon quantum dots (NCQDs) with significant enhancement in photocatalytic activity. Using a solar light generator under ambient conditions with no extra oxygen gas added, we observed the evolution reaction of the model pollutant (methylene blue) in real time. Tailoring of the light absorption to match that of the solar spectrum was achieved by a combination of materials of nano-TiO2 hybrids of nitrogen-doped carbon quantum dots and graphene in its reduced form with a photocatalytic rate constant of ca. 25 × 10−5 s−1. Using a diversity of state-of-the-art techniques including high-resolution transmission electron microscopy, transient photoluminescence, X-ray photoelectron spectroscopy and high accuracy, sophisticated hybrid density functional theory calculations we have gained substantial insight into the charge transfer and modulation of the energy band edges of anatase due to the presence of graphene or carbon dots, parameters which play a key role in improving drastically the photocatalytic efficiencies when compared to pristine titania. More importantly, we prove that a combination of features and materials displays the best photocatalytic behaviour. This performance is delivered in a greener synthetic process that not only produces photocatalytic materials with optimised properties and tailored visible light absorption and efficiency but also provides a path to industrialization.
Westhead O, Barrio J, Bagger A, et al., 2023, Near ambient N2 fixation on solid electrodes versus enzymes and homogeneous catalysts, Nature Reviews Chemistry, Vol: 7, Pages: 184-201, ISSN: 2397-3358
The Mo/Fe nitrogenase enzyme is unique in its ability to efficiently reduce dinitrogen to ammonia at atmospheric pressures and room temperature. Should an artificial electrolytic device achieve the same feat, it would revolutionise fertilizers and even provide an energy dense, truly carbon-free fuel. This Review provides a coherent comparison of recent progress made in dinitrogen fixation on (i) solid electrodes, (ii) homogeneous catalysts and (iii) nitrogenases. Specific emphasis is placed on systems for which there is unequivocal evidence that dinitrogen reduction has taken place. By establishing the cross-cutting themes and synergies between these systems, we identify viable avenues for future research.
Westhead O, Barrio J, Bagger A, et al., 2023, Near ambient N-2 fixation on solid electrodes versus enzymes and homogeneous catalysts (vol 7, pg 184, 2023), NATURE REVIEWS CHEMISTRY, Vol: 7, Pages: 225-225
Mercer MP, Nagarathinam M, Gavilán-Arriazu EM, et al., 2023, Sodiation energetics in pore size controlled hard carbons determined via entropy profiling, Journal of Materials Chemistry A, Vol: 11, Pages: 6543-6555, ISSN: 2050-7488
Hard carbons show considerable potential as anode materials in emerging sodium-ion battery technologies. Recent work suggests sodiation of hard carbon proceeds by insertion of sodium at defects, within the interlayers and inside the nanopores. The energetics of these processes dictate the characteristic sloping region and plateau when hard carbon is charged/discharged with sodium. However, the driving forces affecting these processes, and particularly sodium filling into nanopores, are under debate and are holding back controlled material optimisation. We apply entropy profiling (EP), where the cell temperature is changed under open circuit conditions, to yield additional insights into sodium insertion in hard carbons of systematically controlled pore size. Features from EP vary with the pore size, allowing us to precisely determine the onset of nanopore filling. Comparing the system entropy and enthalpy data to models, we can quantify the energetics of sodium inside the nanopores. The average binding energy of sodium in the pores is found to be inversely proportional to the pore radius of curvature, which is attributed to the scaling of the surface area to volume inside the pores. This simple structure-property relationship provides a rational framework to tune the cell cut-off voltage of sodium-ion cells based on hard carbon, potentially enabling future materials of improved safety and longevity.
Spry M, Westhead O, Tort R, et al., 2023, Water increases the Faradaic selectivity of Li-mediated nitrogen reduction, ACS ENERGY LETTERS, Vol: 8, Pages: 1230-1235, ISSN: 2380-8195
The lithium-mediated system catalyzes nitrogen to ammonia under ambient conditions. Herein we discover that trace amount of water as an electrolyte additive─in contrast to prior reports from the literature–can effect a dramatic improvement in the Faradaic selectivity of N2 reduction to NH3. We report that an optimal water concentration of 35.9 mM and LiClO4 salt concentration of 0.8 M allows a Faradaic efficiency up to 27.9 ± 2.5% at ambient pressure. We attribute the increase in Faradaic efficiency to the incorporation of Li2O in the solid electrolyte interphase, as suggested by our X-ray photoelectron spectroscopy measurements. Our results highlight the extreme sensitivity of lithium-mediated N2 reduction to small changes in the experimental conditions.
Tort R, Westhead O, Spry M, et al., 2023, Nonaqueous Li-mediated nitrogen reduction: taking control of potentials, ACS Energy Letters, Vol: 8, Pages: 1003-1009, ISSN: 2380-8195
The performance of the Li-mediated ammonia synthesis has progressed dramatically since its recent reintroduction. However, fundamental understanding of this reaction is slower paced, due to the many uncontrolled variables influencing it. To address this, we developed a true nonaqueous LiFePO4 reference electrode, providing both a redox anchor from which to measure potentials against and estimates of sources of energy efficiency loss. We demonstrate its stable electrochemical potential in operation using different N2- and H2-saturated electrolytes. Using this reference, we uncover the relation between partial current density and potentials. While the counter electrode potential increases linearly with current, the working electrode remains stable at lithium plating, suggesting it to be the only electrochemical step involved in this process. We also use the LiFePO4/Li+ equilibrium as a tool to probe Li-ion activity changes in situ. We hope to drive the field toward more defined systems to allow a holistic understanding of this reaction.
Westhead O, Spry M, Bagger A, et al., 2023, The role of ion solvation in lithium mediated nitrogen reduction ( Nov, 10.1039/D2TA07686A, 2022), Journal of Materials Chemistry A, Pages: 1-1, ISSN: 2050-7488
Guo Q, Zhao Q, Crespo-Otero R, et al., 2023, Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, ISSN: 0002-7863
Chen Y, Li F, Guo Z, et al., 2022, Sustainable and scalable fabrication of high-performance hard carbon anode for Na-ion battery, JOURNAL OF POWER SOURCES, Vol: 557, ISSN: 0378-7753
Zhang Y, Miao N, Xin X, et al., 2022, Boosting the photocatalytic performance via defect-dependent interfacial interactions from electrostatic adsorption to chemical bridging, NANO ENERGY, Vol: 104, ISSN: 2211-2855
Ng KL, Maciejewska BM, Qin L, et al., 2022, Direct Evidence of the Exfoliation Efficiency and Graphene Dispersibility of Green Solvents toward Sustainable Graphene Production, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN: 2168-0485
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Latham KG, Edathil AA, Rezaei B, et al., 2022, Challenges and opportunities in free-standing supercapacitors research, APL Materials, Vol: 10, Pages: 1-14, ISSN: 2166-532X
The design of commercial supercapacitors has remained largely unchanged since the 1970s, comprising powdered electrodes housed in rigid metal cylinders or pouches. To power the next generation of integrated technologies, an evolution in supercapacitor materials and design is needed to create multifunctional materials that allow energy storage while imparting additional material properties (e.g., flexibility and strength). Conductive free-standing electrodes produced from fibers or 3D printed materials offer this opportunity as their intrinsic mechanical properties can be transferred to the supercapacitor. Additionally, their conductive nature allows for the removal of binders, conductive agents, and current collectors from the supercapacitor devices, lowering their economic and environmental cost. In this Perspective, we summarize the recent progress on free-standing supercapacitors from new methods to create free-standing electrodes to novel applications for these devices, together with a detailed discussion and analysis on their electrochemical performance and physicochemical and mechanical properties. Furthermore, the potential directions and prospects of future research in developing free-standing supercapacitors are proposed.
Barrio J, Pedersen A, Favero S, et al., 2022, Bioinspired and Bioderived Aqueous Electrocatalysis, CHEMICAL REVIEWS, ISSN: 0009-2665
Luo H, Yukuhiro VY, Fernandez PS, et al., 2022, Role of Ni in PtNi Bimetallic Electrocatalysts for Hydrogen and Value-Added Chemicals Coproduction via Glycerol Electrooxidation, ACS CATALYSIS, Vol: 12, Pages: 14492-14506, ISSN: 2155-5435
Wang J, Xu Z, Zhang Q, et al., 2022, Stable Sodium-Metal Batteries in Carbonate Electrolytes Achieved by Bifunctional, Sustainable Separators with Tailored Alignment, ADVANCED MATERIALS, ISSN: 0935-9648
Martin-Martinez FJ, Yeo J, Ryan JW, et al., 2022, Editorial: Biobased nanomaterials: New trends and applications, Frontiers in Chemistry, Vol: 10
Beaucamp A, Muddasar M, Amiinu IS, et al., 2022, Lignin for energy applications - state of the art, life cycle, technoeconomic analysis and future trends, Green Chemistry, Vol: 24, Pages: 8193-8226, ISSN: 1463-9262
Lignin is produced in large quantities as a by-product of the papermaking and biofuel industries. Lignin is the most abundant aromatic biopolymer on the planet with its chemical structure rendering it ideal for carbon materials production and finely tailored architectures of these sustainable carbon materials are beginning to find use in high value energy applications. This review focuses on lignin chemistry, various lignin extraction and fractionation techniques, and their impact on lignin structure/property relationships for energy applications are discussed. Chemistries behind important and emerging energy applications from recent research on this increasingly valuable sustainable polymer are described.
Titirici M-M, Szilagyi PA, 2022, Hydroxide ion-conducting metal-organic frameworks for anion-exchange membrane applications, MATERIALS ADVANCES, Vol: 3, Pages: 8815-8829
Olsson E, Cottom J, Alptekin H, et al., 2022, Investigating the Role of Surface Roughness and Defects on EC Breakdown, as a Precursor to SEI Formation in Hard Carbon Sodium-Ion Battery Anodes., Small, Vol: 18
Hard carbon (HC) anodes together with ethylene carbonate (EC)-based electrolytes have shown significant promise for high-performing sodium-ion batteries. However, questions remain in relation to the initial contact between the carbon surface and the EC molecules. The surface of the HC anode is complex and can contain both flat pristine carbon surfaces, curvature, nanoscale roughness, and heteroatom defects. Combining density functional theory and experiments, the effect of different carbon surface motifs and defects on EC adsorption are probed, concluding that EC itself does not block any sodium storage sites. Nevertheless, the EC breakdown products do show strong adsorption on the same carbon surface motifs, indicating that the carbon surface defect sites can become occupied by the EC breakdown products, leading to competition between the sodium and EC fragments. Furthermore, it is shown that the EC fragments can react with a carbon vacancy or oxygen defect to give rise to CO2 formation and further oxygen functionalization of the carbon surface. Experimental characterization of two HC materials with different microstructure and defect concentrations further confirms that a significant concentration of oxygen-containing defects and disorder leads to a thicker solid electrolyte interphase, highlighting the significant effect of atomic-scale carbon structure on EC interaction.
Xu BB, Jiang Y, Liu TX, et al., 2022, Beyond Lithium: A New Era of Sustainable Energy Engineering., Small, Vol: 18
Guo Z, Cheng G, Xu Z, et al., 2022, Sodium Dual-Ion Batteries with Concentrated Electrolytes, CHEMSUSCHEM, ISSN: 1864-5631
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