A stable solid electrolyte interphase (SEI) plays a vital role in the cyclic stability and Coulombic efficiency (CE) of high-performance lithium-sulfur (Li-S) batteries. It is recognized that the LiNO3 additive can stabilize the SEI of the lithium electrode. However, the exact mechanism of the LiNO3 additive on the SEI of the lithium electrode remains unclear. In this work, we first revealed the mediation mechanism of LiNO3 additive on the dynamic evolution of the SEI on a lithium anode surface through in situ Fourier transform infrared (FTIR) spectroscopy and ab initio molecular dynamics (AIMD) methods. The FTIR and AIMD results directly proved that LiNO3 can accelerate the reduction of lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) into small molecules rich in Li2O on lithium anode, thus forming a compact and stable SEI after immersing in the LiNO3-containing electrolyte. Moreover, the decomposition of LiTFSI and the solvent is hindered in the subsequent lithium deposition stripping process due to the stable SEI, thus leading to higher Coulombic efficiency and long-term cyclic stability. In addition, an ROSO2Li-like intermediate is also observed during the lithium deposition process while decomposing or diffusing away during the lithium stripping process, maintaining a dynamic formation/dissolution equilibrium of the SEI. This research provides a new insight into understanding the role of LiNO3 in stabilizing lithium electrode.

A three-dimensional (3D) electrode was successfully fabricated by coating carbon felt substrate with PbO2 using an electrodeposition method. Compared with the conventional planar Ti/SnO2-Sb/PbO2 electrode, the CF/PbO2 electrode displayed superior electrocatalytic performance for the degradation of phenol, with an 11.2 times higher rate constant. The improved performance was due to its larger active surface area, enrichment of phenol on the surface due to adsorption, and enhanced mass transfer with the porous 3D structure. It also exhibited an 11.4 times higher current efficiency and a 9.1 times lower energy consumption due to the superior electrocatalytic activity and a higher oxidation potential to hinder oxygen evolution. Moreover, the generation rate of center dot OH from CF/PbO2 was 1.3 times higher than that of the Ti/SnO2-Sb/PbO2 electrode. The surface chemistry on the CF/PbO2 electrode during phenol degradation was explored by in situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) characterization, with aromatic intermediates and carboxylic acids identified as key reaction intermediates. This composite electrode also presented excellent long-term stability and durability and negligible leaching of Pb cation, demonstrating as a promising electrode for the electrocatalytic degradation of refractory pollution in wastewater treatment.

Overcoming the energy barrier in CO2 reduction is a key avenue in the development of sustainable carbon capture and recycling systems spearheading against the climate emergency. Diamond, a wide-bandgap material, has shown promise in this aspect due its ability to produce highly reductive solvated electrons when irradiated with deep UV light. This requirement for high-energy optical illumination, however, hampers its sustainable application and limits its useful lifetime. Here we show the photosensitization of nanoscale detonation diamond in reductive photoelectrocatalysis through surface functionalisation with a ruthenium-based dye, demonstrating solar-light driven turnover of CO2 using the unique properties of diamond. The hybrid photosensitizer-nanodiamond materials demonstrated good colloidal and photochemical stability. The nature of electronic conjugation between diamond and photosensitizer was elucidated through X-ray absorption, transient optical absorption, and ultraviolet photoemission spectroscopies, with CO2 turnover significantly improved under solar conditions for photosensitized systems. The potential for photoexcited electron transfer (PET) mediated photosensitization in reductive diamond catalysis opens the way for further sustainable applications using diamond as a sustainable photoelectrocatalyst.

Seaweed fibre is usually discarded as biomass waste after extraction of useful ingredients from seaweed. However this seaweed fibre, a natural abundant cellulose material with uniform dimensions 10 times smaller than other plant-based fibre can be utilized as electrode material for energy storage. In this work, we converted seaweed fibre into conductive carbon electrodes by a thermal carbonisation method. The morphology, chemical composition and conductivity are highly influenced by the carbonisation temperature. In comparison to other biomass sources such as cotton pulp, seaweed fibre is finer, smoother and more conductive at low carbonisation temperature. These carbonized seaweeds were then used as a supercapacitor, giving a high supercapacitance (226.3 Fg −1 ) at the carbonisation temperature of 900°C, and good stability within 2400 cycles. This specific capacitance is significantly higher than values obtained from filter paper or cotton pulp.

2D nanosheets give enhanced surface area to volume ratios in particle morphology and they can also provide defined surface sites to disperse foreign atoms. Placing atoms of catalytic interest on 2D nanosheets as Single Atom Catalysts (SAC) represents one of the novel approaches due to their unique but tunable electronic and steric characteristics. Here in this mini-review, we particularly highlight some recent and important developments on heteroatom doped MoS2 nanosheets (SAC-MoS2) as catalysts for the electrochemical hydrogen evolution reaction (HER) from water, which could lead to opening up to a flagship of important renewable technologies in future. It is shown that the nature of dopants, doping positions and the polytypes of MoS2 nanosheets are the determining factors in the overall catalytic abilities of these functionalised nanosheets. This may serve to obtain atomic models which lead to further understanding of the 'metal-support interaction' in catalysis.

There has been a substantial research effort worldwide to develop non-noble metal catalysts for H2 production from water splitting using renewable energy sources, but most data were evaluated by voltammetry in laboratories. Here, exposed basal planes of MoS2 monolayer nanosheets with metal dopants across the first transition metal (TM) series in the periodic table (Fe, Co, Ni, Cu) are used as cathode catalysts for the proton-exchange membrane (PEM) water splitting in an electrolyzer under typical conditions of strong acidity with more negative applied voltage. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis and high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM) images show a direct proof on the single TM atoms residing at the surface basal sites, which subtly modify the electrocatalytic activity of the monolayer MoS2, depending on their electronic and metal-hydrogen binding ability. We report that Co-sMoS2 yields the highest current density in an electrolyzer with the hydrogen evolution reaction (HER) activity comparable with that of the commercial 20 wt% Pt/C under industrial applicable conditions. A general trend for the other TMs has also been established as evidenced by the change in TM effective nuclear charge across the periodic table, which perturbed the TM-Mo interaction and hence affects the HER activity.

2D nanosheets give enhanced surface area to volume ratios in particle morphology and they can also provide defined surface sites to disperse foreign atoms. Placing atoms of catalytic interest on 2D nanosheets as Single Atom Catalysts (SAC) represents one of the novel approaches due to their unique but tunable electronic and steric characteristics. Here in this mini-review, we particularly highlight some recent and important developments on heteroatom doped MoS2 nanosheets (SAC-MoS2) as catalysts for the electrochemical hydrogen evolution reaction (HER) from water, which could lead to opening up to a flagship of important renewable technologies in future. It is shown that the nature of dopants, doping positions and the polytypes of MoS2 nanosheets are the determining factors in the overall catalytic abilities of these functionalised nanosheets. This may serve to obtain atomic models which lead to further understanding of the 'metal-support interaction' in catalysis.

Novel pseudocapacitive nanomaterials storing energy electrochemically through surface redox reactions have been extensively investigated as an electrode to increase both power and energy density. The pyrolysis of metal-organic frameworks (MOFs), assembled from metal ions and organic ligands, generates well dispersed metal oxides within the carbon with high surface area. Herein, we report the synthesis of CoMn 2 O 4 /Co/MnO @rice husks (RHs) by pyrolysis of two different-sized bimetallic Co/Mn-MOFs@RHs and their electrochemical performance. SEM and PXRD analysis showed that Mn(CH 3 CO 2 ) 2 /Co(NO 3 ) 2 -derived MOF-74 ( 1 ) has much smaller crystal size and grain size than those of MnCl 2 /Co(NO 3 ) 2 -derived MOF-74 ( 2 ) although both have an identical phase. The different crystal sizes of 1 and 2 were rationalized by considering the nucleophilic reactivity of the counter anions to the metal cations. For instance, acetate during the crystallization of 1 has a higher nucleophilic reactivity than chloride during that of 2 in DMF, hence acetate is less readily solvated. Consequently, the smaller crystal size of 1 means a higher loading capacity inside the channels of the RHs compared to 2 since the larger crystal size of 2 can block the channels of the RHs and lead to lower loading capacities. The pyrolysis of 1 @RH and 2 @RH generates CoMn 2 O 4 /Co/MnO mixtures inside the RHs, which work as pseudocapacitive nanomaterials. Interestingly, the electrochemical performance of 1 _C@RHs is superior to that of 2 _C@RHs even though they have a similar surface area. The high capacitance of 1 _C@RHs across all scan rates is attributed to the high loading amount of metal/metal oxide in RHs, high mesopore volume and good electrical contact. Furthermore, the smaller crystals size of 1 than that of 2 prevents the blockage of micrometer-scale channels of RHs, and increases the loading amount of 1 and the mesopore volume. Therefore, the crystal size control of MOFs in RHs is crucial to improve the electrochemical performance of pseudocapacitive nanomaterials. We believe that the impregnation of well-organized MOFs in biomass carbons could contribute the design of novel energy storage devices with high performance.

We report a novel electrochemical approach for synthesizing colloidal silver in an aqueous phase by a hemoglobin-modified boron-doped diamond electrode. The resulting Ag nanoparticles are within 10 nm in size and highly monodisperse with minimal electrode deposition. We also introduce a method for measuring the yield of synthesized nanoparticles using square-wave voltammetry as an alternative to UV-vis spectroscopy. More than 50% of the transferred electrons contributed directly to the formation of silver nanoparticles. This high yield indicates that such electrochemical synthesis is an efficient one-pot method for producing colloidal silver free of toxic reagents and offers a path toward green metal nanoparticle synthesis in solution. A comparative study using alternative electrodes, modifiers, and surfactants suggests a mechanism for the formation of silver nanoparticles mediated by hemoglobin-modified boron-doped diamond electrodes.

Bisphenol A (BPA) is a chemical found in polycarbonate plastics and epoxy resins which is biologically harmful and toxicologically relevant at low doses. Electrochemical sensors offer rapid and accurate detection of bisphenols but suffer from electrode fouling. Boron-doped diamond is known for its exceptional capability to resist chemical fouling due to the weak molecular adsorption of sp(3) carbon. In this work, we use nanodiamond to overcome electrode fouling and detect BPA with a low detection limit at 5 nM. Further, we demonstrate the use of nanocarbon-modified electrodes for BPA detection. One-time use nanocarbon electrodes detect BPA through direct oxidation of BPA in a sensitive and reproducible fashion. For continuous monitoring of BPA, we introduce a new approach based on the detection of the by-product of BPA oxidation, hydroquinone (HQ), which acts as a proxy for BPA quantitation without the need of electrode replacement. These findings aim to tackle the challenges of increasing concern of BPA food and water contamination, as an alternative to the more costly and time consuming central laboratory tests. (C) 2020 Elsevier Ltd. All rights reserved.

The synthesis of nanostructured sub-microspheres of TiO2 anatase with hierarchical nano- and mesoporosity was successfully achieved by using an innovative approach that applies the principles of acidic digestion to microwave (MW) solvothermal synthesis. This process, termed flash microwave-assisted solvothermal (FMS) synthesis, facilitates the formation of spherical particles without surfactants or templating agents, exploiting the rapid reaction kinetics engendered by MW heating. Unlike many other MW-assisted solvothermal methods, the application of constant MW power leads to a rapid increase of the autogenous pressure, inducing burst-nucleation of small primary crystallites and subsequent rapid agglomeration into secondary particles, with reaction times reduced to minute-timescales. The use of non-aqueous polar solvents such as ethanol is key to the production of regular spheres with a narrow size distribution, composed of nanocrystallites. Morphology, porosity, specific surface area, phase composition, crystallite size and optical properties of the particles can be controlled via a judicious selection of physical and chemical synthesis parameters, especially precursor choice and acid concentration. The complex structure of the particles leads to surface areas of up to ca. 500 m2 g-1 with intergranular mesoporosity. The as-synthesised FMS particles show increased adsorption under dark conditions and selective de-ethylation of rhodamine B under visible light compared to a commercial photocatalyst (Degussa P25). The photodegradation mechanism hinges on the capacity of the spheres to accept electrons from the photoexcited state of molecules at the particle surface, with the large sphere surface area maximising adsorption capacity and improving the efficiency of the photocatalytic processes. The singular characteristics and properties of the particles could pave the way for further applications in water purification and optoelectronic devices.

Conductive, boron doped diamond (BDD) is an extraordinary material with many applications in electrochemistry due to its wide potential window, outstanding robustness, low capacitance and resistance to fouling. However, in photoelectrochemistry, BDD usually requires UV light for excitation, which impedes e. g., usage in CO(2)to fuel reduction. In this work, a heavily boron doped, nanostructured diamond electrode with enhanced light absorption has been developed. It is manufactured from BDD by reactive ion etching and presents a coral-like structure with pore diameters in the nanometer range, ensuring a huge surface area. The strong light absorbance of this material is clearly visible from its black color. Consequently, the material is calledDiamond Black(DB). Electrochemical and X-ray photoelectron spectroscopy measurements performed at near-ambient pressure conditions of water vapor demonstrate increased surface reactivity for the hydrogen-terminated DB compared to oxidized surfaces. Depending on the surface termination, the wettability and hence the electrochemically accessible area can be changed. Photoelectrochemical conversion of CO(2)was demonstrated using a Cu2O-modified electrode in ionic liquids under solar illumination. High formic acid production rates at low catalyst deposition times can be obtained paired with an increased catalyst stability on the DB surface.

This work compares pulse and cyclic voltammetry deposition of Au particles on boron doped diamond electrodes for determination of nitrite. Gold particles of different sizes from nanometer to submicron with different morphologies from sphere to star shape are obtained using different deposit parameters for optimization of nitrite detection. The nitrite sensing experiments via the amperometry method show that a better limit of detection for gold particles decorated by the pulse deposition, thus demonstrating a benefit of using this method for electroanalysis.

Hydrogen evolution reaction (HER) is one of the most critical reactions in fuel chemistry to produce clean and sustainable hydrogen gas as a renewable energy source. Nowadays, HER has always been catalysed with costly Pt or Pd metal1. To reduce the cost but still maintain a satisfactory performance, studies on Pt/Pd free catalysts for HER have never ceased. In the present work, we explore the electrodeposition of three morphologies (polyhedral, dendritic, and spherical) of Ag nanoparticles on boron-doped diamond electrodes (BDDEs) in various electrochemical conditions including deposition potential and deposition time. Specifically, by varying the deposition potentials of the single-stepped electrochemical deposition, a morphological change from polyhedral to homogeneous dendritic Ag was observed. The high deposition potential would drive the formation of dendritic Ag, which is a thermodynamically unfavourable structure with high surface energy. On the other hand, a two-stepped deposition mechanism was performed to synthesize spherical Ag nanoparticles. This two-stepped mechanism, which was used in synthesising small Au nanoparticles with high coverage by F. Bottari et al., contains a nucleation step at a more negative potential, and a growth step at a less negative potential.2 The sizes of each type of Ag nanoparticles were confirmed by Scanning Electron Microscopy (SEM), and the surface compositions were verified by X-Ray Photoelectron Spectroscopy (XPS). The current densities for HER catalysis were investigated using Linear Sweep Voltammetry (LSV), and a connection between morphologies and catalytic activities was drawn. All three types of Ag modified BDDEs showed better catalytic performance compared to that of drop-coated colloidal Ag-BDDE with comparable coverage and bare BDDE. Notably, spherical Ag-NP modified BDDE with an average particle diameter of 75nm has the highest percentage of pure elemental silver and showed the best performance as well as high stability in HER catalysis, which can be a less expensive yet efficient alternative for Pt/Pd containing catalysts. References: Walter, M.; Warren, E.; McKone, J.; Boettcher, S.; Mi, Q.; Santori, E.; Lewis, N. Chemical Reviews2010, 110, 6446-6473. Bottari, F.; De Wael, K. Journal of Electroanalytical Chemistry 2017, 801, 521-526.

There has been an intense research effort to develop 2-H MoS2 based catalysts to reduce or eliminate the use of Pt/C at higher metal loading for the hydrogen evolution reaction (HER) in catalytic hydrolysis of water, which enables the capture of renewable energy sources as fuel and chemical. However, the study of its uncommon polymorph, 1T-MoS2, and particularly the doping effect with transition metal (TM) is rather limited due to the instability of this phase. Here, we report a simple ambient temperature modification method using sonication to dope the single layer 1T-(MoS2)-Mo-S with various TM precursors. It is found that 1T-(MoS2)-Mo-S is more active than corresponding 2H-(MoS2)-Mo-S and the inclusion of 3 wt % Pt or Pd can also further enhance the HER activity. STEM-EELS and XAS show that the active single TM atom doping on this surface accounts for the high activity. Kinetic and DFT analyses also illustrate that the metallic nature of 1T-(MoS2)-Mo-S greatly facilitates the proton reduction step from water, rendering it non-rate-limiting in contrast to that of 2H-(MoS2)-Mo-S. The inclusion of the TM single doper such as Pd, despite at low loading, can offer the dramatic acceleration of the rate limiting recombination of H to H-2. As a result, a bifunctional catalysis for HER over this tailored composite structure is demonstrated that outperforms most reported catalysts in this area.

The electrooxidation of sulphite has been studied in acid solution on a boron doped diamond electrode modified by gold nanoparticles. The Au nanoparticles are deposited by pulse deposition which involves nucleation and growth steps. The morphology evolves from sphere to dendrite with the increasing of growth time. Simultaneously the interparticle distance decreases leading to the high overlapping of diffusion layer of each Au particle and therefore the formation of a linear planar diffusion. The voltammetry for sulphite oxidation shows the dependence of the square root of scan rates and concentrations. When the concentration is decreased, the current of reverse reduction peak emerges, suggesting an EC2 mechanism (a one-electron transfer process followed by a dimerization chemical reaction). The digital simulation fits the experimental voltammograms well, further confirming the proposed mechanism.

Carbamate and organophosphate compounds are widely used pesticides because of their high insecticidal activity, and sometimes as nerve agents because of their crippling inhibition of the enzyme acetylcholinesterase (AChE)1. These compounds accumulate in the food chain and can hijack the nervous system of the target organisms indiscriminately. Traditional electrochemical methods of pesticide detection rely on layered structures atop noble metal or carbon electrodes to assist the loading of AChE, which produces currents proportional to its inhibition level. One of the clear advantages of boron-doped diamond (BDD) as an electrode material is its greater potential window in aqueous solutions, compared to conventional electrode materials2. This allows redox behaviour at extended potentials to be observed without damage to the electrode. Cyclic, differential-pulse, and square-wave voltammetric techniques were used to probe carbaryl (CB), carbofuran (CF), and malathion in Carmody buffers of pH 2–12. Oxidation of CF occurred at the three overpotentials 1.31 V, 1.44 V, and 1.69 V, and a broad reduction peak was observed at 1.10 V, referred against Ag|AgCl. Compared with the oxidation of CB at 1.35 V, these electrochemical differences allowed for simultaneous detection of both compounds. This non-enzymatic sensor demonstrated a linear calibration over a concentration range of 1–100 µM for CB (R=0.9834) and CF (R=0.9938). After exposure to 1 mM malathion, a reduction peak appears that is highly sensitive to pH, attributed to a complex carbon–oxygen adsorbate that is robust to aggressive cleaning methods and only removable by hydrogen plasma etching. This malathion modified surface may be advantageous in future applications such as pH sensing. The oxidised BDD demonstrated failsafe reproducibility, a linear response, and low detection limits at medically relevant concentrations. References Kostelnik, P. Kopel, A. Cegan, M. Pohanka, Sensors, 17 (2017) 676. V. Macpherson, Phys. Chem. Chem. Phys., 17 (2015) 2935-2949.

Novel hybrid nanomaterials comprising metal-organic framework compounds carbonised in the presence of biomass material derived from rice husk have been investigated as a new class of sustainable supercapacitor materials for electrochemical energy storage. Specifically, two synthetic routes were employed to grow Co/Mn metal-organic framework compounds in the channels of rice husks, which had been activated previously by heat treatment in air at 400 °C to produce a highly porous network. Pyrolysis of these hybrid materials under nitrogen at 700 °C for 6 h produced metal-containing phases within the nanocarbon, comprising intimate mixtures of Co, MnO and CoMn2O4. The materials thus produced are characterized in detail using a range of physical methods including XRD, electron microscopy and X-ray photoelectron spectroscopy. The synthetic pathway to the metal-organic framework compound is shown to influence significantly the physical properties of the resulting material. Electrochemical evaluation of the materials fabricated revealed that higher specific capacitances were obtained when smaller crystallite sized bimetallic Co/Mn-MOFs were grown inside the rice husks channels compared to larger crystallite sizes. This was in-part due to increased metal oxide loading into the rice husk owing to the smaller crystallite size as well as the increased pseudocapacitance exhibited by the smaller crystallite sizes and increased porosity.

Surface sites of extensive exposed basal planes of MoS2 nanosheets for the first time have been doped with isolated transition metal atoms as 2D monolayer catalysts for the electrochemical hydrogen evolution reaction (HER). Our HAADF-STEM images clearly show that single transition metal atoms are situated on these multiple surface basal sites that subtly modify the electro-catalytic activities of the monolayer MoS2 dependent on the electronic and stereospecific properties. From the results of DFT calculations, it is found that these dopers play important roles in tuning the hydrogen adsorption enthalpies on exposed surface S atoms and Mo atoms in HER. Our electrochemical testing, characterization and computational modelling demonstrate that Co can significantly enhance the HER activity by the dominant Co-S interaction whereas Ni substantially lowers the HER rate due to the Ni-Mo interaction on the same basal site despite the two transition metal elements are neighbored to each other in the periodic table. We believe that both the geometric and electronic factors exerted by transition metal dopants are important parameters in further tuning the 2D MoS2 structure for rational design of the composite materials for more efficient electrochemical hydrogen production from water.

The Cover Feature illustrates the electrochemical synthesis of novel bimetallic Pd–Ni nanoparticles on an oxygen-terminated boron-doped diamond substrate for use as an electrocatalyst in a direct ethanol fuel cell. This synthetic method allows the electrocatalytic properties and synergistic effects of the interfaces on the nanostructured metallic surface to be enhanced while significantly reducing the noble metal loading in the electrocatalyst. More information can be found in the Article by C. K. Mavrokefalos et al. on page 456 in Issue 3, 2018 (DOI: 10.1002/celc.201701105).