A three-component catalyst material has been developed for the hydrogen evolution reaction (HER) from preformed DNA-cisplatin (cisPt) adducts functionalised on single-walled carbon nanotubes (SWCNTs) under acidic conditions (pH 3). The DNA was used as a scaffold for platinum placement at ultra-low loadings, sourced from the anticancer drug cisplatin (cisPt). The SWCNTs were successfully functionalised with DNA, cisPt, and DNA-cisPt adducts, with each evaluated for their catalytic performance for HER. The dispersion efficiency of the nanotube functionalisation process was optimised as a function of the molar ratio of SWCNT to DNA-cisPt and the sonication time employed, with 1 : 1 and 45 minutes respectively proving optimal. Scanning Transmission Electron Microscopy (STEM) was used to study the resulting changes to the surface morphology for each condition. Overall, the reaction time of the functionalisation process had a greater influence on the resulting platinum nanocluster size than the employed molar ratio of SWCNT to DNA-cisPt. Cyclic voltammetry measurements revealed that the highest mass activity for the HER could be attained through functionalisation of SWCNTs with DNA-cisPt adducts as opposed to with cisPt alone, validating the essential role of DNA in this catalyst design. The activity was found to correlate to the Pt nanocluster size and distribution, which was optimal at a 1 : 1 molar ratio of SWCNT to DNA-cisPt. The importance of the role of both the DNA and the SWCNTs was validated via the mass activity measurements of the Pt, with the performance attained for the three-component SWCNT-DNA-cisPt catalyst (18.4 ± 0.9 mA mg-1Pt) being higher than that for SWCNT-cisPt (11.9 ± 0.6 mA mg-1Pt), DNA-cisPt (10.0 ± 0.5 mA mg-1Pt) and bulk cisPt (7.4 ± 0.4 mA mg-1Pt). The superior activity is consistent with optimized Pt dispersion in the 1 : 1 SWCNT to DNA-cisPt combination. While the measured nanocluster size of the three-component system (1.23 ± 0.65 nm) is statistically similar to that of SWCNT-cisPt (1.27 ± 0.46 nm) in the absence of DNA, the nucleic acid scaffold appears to promote more effective utilization of Pt active sites.

Herein we demonstrate the use of magnetron-sputtered, low weight-loading platinum on carbon black catalysts as a pathway to reducing mass of platinum in electrolyser and fuel cell applications. In contrast to wet chemical methods, which often require multi-step syntheses involving toxic chemicals and washing post synthesis, magnetron sputtering can produce catalysts for use immediately after production. Scanning transmission electron microscope (STEM) analysis shows these bespoke catalysts possess a bimodal distribution of particle sizes, with nanoparticles approximately half the size of commercial equivalents (ca.1 vs > 2 nm) and a distinct distribution of single metal atoms, dimers and trimers. Measurement of the electrochemically active surface area (ECSA) revealed a higher surface area across all fabricated catalysts, ranging from 17 % to 51 % higher than commercial equivalents. This increased surface area provides a comparable hydrogen evolution reaction (HER) onset potential at a fraction of the platinum loading, indicating both that kinetics are not affected measurably by changes in platinum size and that the Pt particles are well dispersed across the support. In contrast, the oxygen reduction reaction (ORR) activity showed clear kinetic differences due to particle size with the onset potential varying by over 100 mV across the catalyst samples, reflecting the influence of stable platinum nanoclusters on catalytic activity. Rotating ring disc electrode (RRDE) voltammetry offered additional insight into the size and dispersion of the platinum nanoclusters across the samples, elucidating differences between them

MoS2 has seen decades of research into enhancing its electrocatalytic activity towards the Hydrogen Evolution Reaction; however, consistently, the literature has been undecided and often contradictory on the true nature of its active sites. Herein, the understanding of MoS2 active sites has been reviewed, collating chemical evidence across the literature using techniques such as XPS, Raman, and electrochemical studies to deduce a more complete picture of the origins of its catalytic activity. A seemingly contradictory literature landscape has been rationalised, concluding that the most accurate data appears to back sulphur defects, and thus low-coordinate Mo sites, as the active sites of interest, alongside demonstrating how parsing the literature in this way can help locate agreement where only contradiction was thought to reside. Following this, learning from the various techniques used in their elucidation is not only beneficial for future work on this material but also for electrocatalyst development as a whole.

This study investigated the preparation of 2D transition metal dichalcogenide (TMD) hybrids via mechanochemical activation and examined their catalytic activity towards the hydrogen evolution reaction (HER). Binary and ternary mixtures of TMD materials were prepared and characterized, focusing on their electrochemical performance. The ternary hybrids exhibited superior HER activity compared to binary hybrids, with MoS2+MoSe2+WS2 demonstrating the lowest onset potential (-0.47 V vs Ag/AgCl). Tafel slope calculations indicated that ternary hybrids generally exhibited lower Tafel values, suggesting enhanced reaction kinetics. Both binary and ternary hybrids followed a Volmer-Heyrovsky mechanism, where the Volmer discharge step was rate-determining for HER. Electrochemical rate constant determination revealed varying values (ranging from 0.52 x 10-3 cm s-1 to 8.2 x 10-3 cm s-1) among the TMD hybrids, with mixtures containing selenium components generally exhibiting higher rate constants than those without. This improvement in catalytic activity was attributed to increased surface area, combined effect of two or more TMDs and potential exfoliation of TMDs during mechanochemical processing, exposing more active sites for HER. These findings underscore the potential of mechanochemically prepared TMD hybrids as efficient HER electrocatalysts.

Magnetron sputtering offers a single-step, flexible, and environmentally friendly fabrication route to catalyst production, avoiding the requirement for complex syntheses or toxic chemicals normally required for more traditional wet chemical techniques. Using this facile method, a nanocluster platinum-on-carbon black catalyst is fabricated, rigorously characterized physically and electrochemically, and compared to a well-understood commercial catalyst (TKK). Scanning transmission electron microscopy (STEM) imaging reveals a mean cluster size of 1.1 ± 0.4 nm, half the commercial equivalent, with an associated electrochemically active surface area (ECSA) of 122.2 ± 9.6 m2 g-1, 40% higher than the commercial comparison. Catalytic performance is measured using the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR); results indicate a turnover frequency (TOF) 33 times higher than the commercial analogue in the HER and distinct kinetic differences between samples in the ORR. Rotating ring disc electrode voltammetry (RRDE) is utilized to study the mechanism further, and a discussion of activity vs size of particle is presented.

Transition metal dichalcogenide (TMD) heterostructures have been discovered to have improved catalytic activity towards the hydrogen evolution reaction (HER). This study explores the stability and HER catalytic activity including reaction kinetics of heterolayers of different TMDs (MoS2, MoSe2 and WS2). The stability of the heterolayers varied with those having an overlayer of electrodeposited MoS2 being more stable as compared to those with MoSe2 overlayer which degraded with each scan in acidic media. Investigation into the HER kinetics of the heterolayers involved Tafel analysis and electrochemical rate constant calculation. There was an improvement in Tafel values calculated in comparison to reported values for these heterolayers. WS2/MoS2 and MoSe2/MoS2 heterolayers registered rate constants of (3.20 ± 0.10) × 10−4 cm s−1 and (1.73 ± 0.03) × 10−4 cm s−1 respectively, which was an improvement of up to an order of magnitude compared to the reported rate constant of electrodeposited MoS2 of (3.17 ± 0.30) × 10−5 cm s−1. All this highlights the improved HER catalytic activity of the heterolayers.

Within single-entity electrochemistry (SEE), the subfield of nano-impact electrochemistry (NIE) has rapidly expanded in recent years with advances in electrocatalysis and nanomaterial fabrication applications. In particular, recent developments concerning the hydrogen evolution reaction and oxygen evolution reaction will be discussed, as two reactions integral to water-splitting for hydrogen production. Moreover, the application of NIE in electrocatalyst fabrication methods will be discussed with a focus on metal deposition onto non-metallic nanoparticles and bimetallic nanoparticles.

The recovery of ruthenium from low-concentration solutions poses a significant challenge due to its scarcity and rising economic value, and nano-impact electrochemistry has emerged as a promising method for efficient recovery of critical metals from solution through deposition during impacts of non-metallic nanoparticles. In this study, we investigate the redox chemistry of ruthenium on carbon black via the impact technique and demonstrate the ability to recover ruthenium from solution. The reduction (electrodeposition) and oxidation of Ru3+ ions in solution onto carbon black nanoparticles can be observed during nano-impacts with the respective onset potentials of these redox processes agreeing with those obtained from solution voltammetry. Upscaled experiments focusing on the electroreduction process, led to the formation of RuOx deposits, confirmed through scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis, X-ray photoelectron spectroscopy (XPS) analysis, and thermogravimetric analysis (TGA). Under partially-optimised conditions, >90 % recovery of Ru(III) from a 1 mM solution was achieved in ca. 8 h.

The field of impactelectrochemistry, namely, electrochemical processesoccurring at nanoparticles during collisions with a substrate electrode,has recently been applied to the recovery of commercially importantmetals. In this study, the reduction and oxidation of solution Mn(II)were observed on carbon black particles during nanoimpacts, with theonset potentials of the reduction and oxidation processes in goodagreement with solution voltammetry. The formation of Mn(0) and MnO2 was confirmed via scanning electron microscopy/energy-dispersiveX-ray (SEM/EDX) analysis and X-ray photoelectron spectroscopy (XPS)analysis. Coverages of between 0.2 and 0.6 monolayer equivalents wereobtained for the reductive deposition of Mn, whereas for the anodicdeposition of MnO2, a more complex picture was found dueto the oxidation pathway from Mn(II) to MnO2.

Microfluidic paper-based analytical devices (µPADs) have been successfully developed using dual detection: electrochemical and colorimetric systems. The µPADs have the potential to be used as Pb(II), Cd(II), and Cu(II) sensors to test the quality of water. The fabrication process uses hot embossing and screen-printing methods. The working electrode in the electrochemical zone was enhanced by the bismuth metal deposition process, while in the colorimetric zone, the gold nanoparticles modified with thioctic acid and dansylhydrazine (TA-Au-DNS) were used as a colorimetric sensor to detect Cu. The basic material of µPADs was characterized using a Fourier-transform infrared (FTIR) and a contact angle meter (CAM). In the electrochemical zone, the signals of square wave anodic stripping voltammetry (SWASV) resulted in good detection of Pb(II) and Cd(II) (from 0 to 100 ppb) with a limit of detection of 1.588 and 1.42 ppb, respectively. In the colorimetric zone, the performance of TA-Au-DNS for detecting Cu metal was obtained from readings through the red-green-blue (RGB) sensor as a miniature of µPADs reader. The LOD, LOQ, and average Vx0 (linearity values) in the detection of Cu(II) (from 58 to 100 ppb) are 8.51 ppb, 28.36 ppb, and 0.41%, respectively.

Recycling of critical materials, regeneration of waste, and responsible catalyst manufacture have been repeatedly documented as essential for a sustainable future with respect to the environment and energy production. Electrochemical methods have become increasingly recognized as capable of achieving these goals, and "impact" electrochemistry, with the advantages associated with dynamic nanoelectrodes, has recently emerged as a prime candidate for the recovery of metals from solution. In this report, the nanoimpact technique is used to generate carbon-supported palladium catalysts from low-concentration palladium(II) chloride solutions (i.e., a waste stream mimic) as a proof of concept. Subsequently, the catalytic properties of this material in both synthesis (Suzuki coupling reaction) and electrocatalysis (hydrogen evolution) are demonstrated. Transient reductive impact signals are shown and analyzed at potentials negative of +0.4 V (vs SCE) corresponding to the onset of palladium deposition in traditional voltammetry. Direct evidence of Pd modification was obtained through characterization by environmental scanning electron microscopy/energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis of impacted particles. This showed the formation of deposits of Pd0 partially covering the 50 nm carbon black particles with approximately 14% Pd (wt %) under the conditions used. This material was then used to demonstrate the conversion of iodobenzene into its biphenyl product (confirmed through nuclear magnetic resonance) and the successful production of hydrogen as an electrocatalyst under acidic conditions (under cyclic voltammetry).

This study demonstrates the possibility of depositing metals onto low-metal content particles via im-pact electrochemistry, a technique used to measure transient current signals (electrochemical impacts) produced from the collision between particles moving under Brownian motion and a potentiostated in-terface (Rees, 2014; Markham et al., 2020; Zhang and Zhou, 2020). The deposition of copper onto the surface of fly-ash cenospheres via electrochemical impacts is reported, along with its deposition onto sil-ver and gold nanoparticles. A comparison with linear sweep voltammetry confirmed that impact signals correlated with deposition potentials (bulk and underpotential deposition). Reductive impact events were observed at potentials negative of -0.3 V (for Ag) and -0.1 V (for Au) (vs. MSE), with evidence for a change in coverage of deposition from ca. 103% at -0.1 V to 261% at -0.8 V vs. MSE for Au. Cenospheres were shown to be sufficiently electrochemically active to facilitate copper deposition, either on modi-fied electrodes or showing transient impact spikes indicating copper deposition, which was confirmed via SEM/EDX and ICP-MS analysis. (c) 2022 The Authors. Published by Elsevier Ltd.

MoS2 materials have been extensively studied as hydrogen evolution reaction (HER) catalysts. In this study nanoparticulate MoS2 is explored as a HER catalyst through impact voltammetry. The onset potential was found to be -0.10 V (vs RHE) at pH 2, which was confirmed to be due to HER by scale-up of the impact experiment to generate and collect a sufficient volume of the gas to enable its identification as hydrogen via gas chromatography. This is in contrast to electrodeposited MoS2, which was found to be stable in pH 2 sulfuric acid solution with an onset potential of -0.29 V (vs RHE), in good agreement with literature. XPS was used to categorize the materials and confirm the chemical composition of both nanoparticles and electrodeposits, with XRD used to analyze the crystal structure of the nanoparticles. The early onset of HER was postulated from kinetic analysis to be due to the presence of nanoplatelets of about 1-3 trilayers participating in the impact reactions, and AFM imaging confirmed the presence of these platelets.

Understanding the interaction between metal nanoclusters and two-dimensional (2D) layered materials presents a route toward the creation and tuning of hybrid materials. Here, we synthesize hybrid materials composed of mass-selected platinum nanoclusters produced using a magnetron sputtering gas aggregation cluster beam source with a lateral time-of-flight mass filter (mass resolution M/Delta M = 20) and large-area tungsten disulfide (WS2) 2D atomic layers. We employ aberration-corrected scanning transmission electron microscopy (STEM) in high-angle annular dark-field (HAADF) mode and micro-Raman spectroscopy to study the interaction between Pt-147 and suspended WS2 atomic layers. HAADF-STEM analysis reveals that soft-landed Pt-147 nanoclusters are situated on top of few-layered WS2 stacks, rather than being embedded or pinned. We observed a red shift in both E-2g and A(1g) modes and striking enhancement of A(1g) mode in the micro-Raman signatures of WS2, which provide evidence that Pt-147 clusters are soft-landed on the WS2 basal plane without disrupting the crystalline structure of the WS2 and of charge transfer from Pt-147 to WS2, respectively. In contrast, the measured change in line width of the E-2g mode of WS2 reveals a strong interaction between Pt-147 and WS2 layers. Direct evidence for the relative stability of Pt-147 clusters on WS2 is assessed by position-dependent Raman profiling and real-time HAADF-STEM imaging. Our approach offers a novel route to the controlled incorporation of size-selected nanoclusters on the 2D WS2 basal plane for catalysis and energy harvesting device applications.

Green hydrogen production can only be realized via water electrolysis using renewable energy sources. Proton exchange membrane water electrolyzers have been demonstrated as the technology of choice for mass production of green hydrogen due to their scalability and potential high efficiency. However, the technology is still relatively expensive due to the catalyst materials cost and operational limitations due to mass transfer and activation polarizations. During the oxygen evolution reaction, oxygen bubbles stick to the electrode surface and this causes a low reaction rate and high mass transfer losses. In this study, the commonly used electrocatalyst for oxygen evolution reactions; IrO2, is modified by introducing magnetic Fe3O4 to achieve greater bubble separation at the anode during operation. The prepared composite catalysts were characterized using Scanning Electron Microscope, Energy Dispersive X-Ray Analysis, X-Ray Powder Diffraction, X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller characterization methods. The modified composite electrocatalyst samples are magnetized to investigate the magnetic field effect on oxygen evolution reaction performance in proton exchange membrane water electrolyzers. 90% IrO2 - 10% Fe3O4 and 80% IrO2 - 20% Fe3O4 samples are tested via linear sweep voltammetry both ex-situ and in-situ in a proton exchange membrane water electrolyzer single cell. According to the linear sweep voltammetry tests, the magnetization of the 80% IrO2 - 20% Fe3O4 sample resulted in 15% increase in the maximum current density. Moreover, the single cell electrolyzer test showed a four-fold increase in current density by employing the magnetized 80% IrO2 - 20% Fe3O4 catalyst.

Iridium‐based oxides, currently the state‐of‐the‐art oxygen evolution reaction (OER) electrocatalysts in acidic electrolytes, are cost‐intensive materials which undergo significant corrosion under long‐term OER operation. Thus, numerous researchers have devoted their efforts to mitigate iridium corrosion by decoration with corrosion‐resistant metal oxides and/or supports to maximize OER catalyst durability whilst retaining high activity. Herein a one‐step, facile electrochemical route to obtain improved IrO x thin film OER stability in acid by decorating with amorphous tungsten sulphide (WS 3− x ) upon electrochemical decomposition of a [WS 4 ] 2− aqueous precursor is proposed. The rationale behind applying such WS 3− x decoration stems from the generation of a tungsten oxide phase, a well‐known corrosion‐resistant photoactive OER catalyst. The study demonstrates the viability of the proposed WS 3− x decoration, allowing the tailoring of experimental parameters responsible for WS 3− x nanoparticle size and surface coverage. OER stability tests coupled by ex situ SEM and XPS corroborate the beneficial effect of WS 3− x decoration, yielding improved OER specific activity metrics along with minimized Ir surface roughening, a characteristic of electrodissolution. Iridium decoration with electrodeposited, corrosion‐resistant oxides is consequently shown to be a promising route to maximize OER stabilities.

This paper demonstrates the significant and positive effect of applying a magnetic field on the performance of Proton Exchange Membrane Water Electrolysers (PEMWE). A magnetizer and a transparent PEMWE cell are used to observe the effect of the magnetic field at variable water flow rates on the PEMWE performance. The presence of the magnetic field introduces Lorentz force which results in a significant improvement in the electrolyser performance. The magnetic flux density is varied between 0 T and 0.5 T, while the water flow rate is varied from 100 ml min(-1) to 300 ml min(-1) to study the effect and relationship between the two parameters and the performance of the PEMWE. Under a 0.5 T magnetic field and 300 ml min(-1) flow rate, a 33% increase in the cell performance is achieved compared to the conventional operation at the same flow rate. The positive effect is explained by the introduction of Lorentz force from the magnetic field to the operating PEMWE. The improvement here is due to the relaxation and pumping effect of the magnetic field on the electrode surface which results in enhancing oxygen bubbles removal and lowering mass transport polarisation. Moreover, the enhanced oxygen bubbles removal is expected to increase the lifetime of the electrolyser as a result of the reduced contact between the produced oxygen and the anode materials.

The electrochemical reduction of oxygen in a range of six polar aprotic solvents is investigated via linear sweep voltammetry at platinum, gold, and carbon fibre microelectrodes. Values for the standard heterogeneous electron transfer rate constant (k(0)) are reported, and in all cases follow the trend with electrode material of k(0)(C) > k(0)(Pt) similar to k(0)(Au). The variation in k(0) with solvent is discussed in terms of the Debye model and a dependence on the longitudinal dielectric relaxation constant (tau(L)) is found of the form k(0) square tau(-0)(L). Static solvent effects are accounted for via consideration of both spherical and connected-spheres models of solvation, and it is found that theta approximate to, 0.65 indicating that the reduction of dioxygen in these solvents is a non-adiabatic outer-sphere electron transfer.

The development of non-Pt hydrogen oxidation reaction catalysts for hydrogen-fuelled polymer electrolyte fuel cells allows for an overall reduction in electrode Pt content and therefore helps reduce the cost of devices, one of the biggest commercial challenges. Herein, a novel ternary alloy catalyst supported on carbon, PdIrAu/C, has been synthesised, characterised and compared to the binary PdIr/C to show how the addition of Au improves the stability of the catalyst. Transmission electron microscopy was utilised to analyse electrode structure as a function of the synthesis method, showing the optimum annealing temperature, of those tested, to be 400 degrees C, while inductively-coupled plasma mass spectrometry provided analysis of the degradation of the two catalysts, confirming the PdIrAu/C catalyst is more stable at potentials similar to those at a fuel cell anode than PdIr/C.

The synthesis and characterisation of novel metal-modified DNA precursors for fuel cell catalyst development are described. Material precursors in the form of metal-DNA complexes were prepared through the reaction of DNA with cisplatin at various loadings and spectroscopically tested to confirm the platinum binding mode and the degree of complexation. The surface morphology of the DNA-metal material was analysed by Scanning Transmission Electron Microscopy (STEM), which revealed the extent of platinum nanocluster formation, with low metal loadings leading to observation of individual platinum atoms. Electrochemical measurements showed a greater electrocatalytic activity for the hydrogen evolution reaction (HER) with increased platinum loadings, shifting the half wave potential, E-1/2, away from the glassy carbon limit towards that of a bulk Pt electrode. This is explained further by Tafel plots, from which a change in the mechanism of the apparent rate limiting step for proton reduction from a Volmer to a Heyrovsky mechanism is postulated as the platinum loading increases.