Patrick Unwin

Patrick Unwin
The University of Warwick · Department of Chemistry

DSc, DPhil, MA, BSc

About

500
Publications
49,729
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21,660
Citations
Citations since 2017
111 Research Items
9213 Citations
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500

Publications

Publications (500)
Article
Anatase TiO2 is a promising material for Li-ion (Li+) batteries with fast charging capability. However, Li+ (de)intercalation dynamics in TiO2 remain elusive and reported diffusivities span many orders of magnitude. Here, we develop a smart protocol for scanning electroche-mical cell microscopy (SECCM) with in situ optical microscopy (OM) to enable...
Article
Anatase TiO2 is a promising material for Li‐ion (Li+) batteries with fast charging capability. However, Li+ (de)intercalation dynamics in TiO2 remain elusive and reported diffusivities span many orders of magnitude. Here, we develop a smart protocol for scanning electroche­mical cell microscopy (SECCM) with in situ optical microscopy (OM) to enable...
Article
Full-text available
Copper (Cu) corrosion is a compelling problem in the automotive sector and in oil refinery and transport, where it is mainly caused by the action of acidic aqueous droplets dispersed in an oil phase. Corrosion inhibitors, such as benzotriazole (BTAH) and its derivatives, are widely used to limit such corrosion processes. The efficacy of corrosion i...
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Dopamine (DA) adsorption and electron-transfer kinetics are strongly sensitive to the structure and composition of carbon electrodes. Activation of carbon surfaces is a popular method to improve DA detection, but the role of carbon structural features on DA behavior remains uncertain. Herein, we use scanning electrochemical cell microscopy (SECCM)...
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Molecular materials must deliver high current densities to be competitive with traditional heterogeneous catalysts. Despite their high density of active sites, it has been unclear why the reported O2 reduction reaction (ORR) activity of molecularly defined conductive metal-organic frameworks (MOFs) have been very low: ca. -1 mA cm-2. Here, we use a...
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We demonstrate how combined in-situ measurements and finite element method modeling can provide new insight into the relative contribution of mass transport to the growth of calcium carbonate on two model surfaces, glass and gold, under high-supersaturation conditions relevant to surface scaling. An impinging jet-radial flow system is used to creat...
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Revealing how formation protocols influence the properties of the solid‐electrolyte interphase (SEI) on Si electrodes is key to developing the next generation of Li‐ion batteries. SEI understanding is, however, limited by the low‐throughput nature of conventional characterisation techniques. Herein, correlative scanning electrochemical cell microsc...
Article
Revealing how formation protocols influence the properties of the solid‐electrolyte interphase (SEI) on Si electrodes is key to developing the next generation of Li‐ion batteries. SEI understanding is, however, limited by the low‐throughput nature of conventional characterisation techniques. Herein, correlative scanning electrochemical cell microsc...
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Full-text available
Understanding how crystallographic orientation influences the electrocatalytic performance of metal catalysts can potentially advance the design of catalysts with improved efficiency. Although single crystal electrodes are typically used for such studies, the one-at-a-time preparation procedure limits the range of secondary crystallographic orienta...
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In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This intrinsic proton conductivity of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is...
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Full-text available
Indium tin oxide (ITO) is a popular electrode choice, with diverse applications in (photo)electrocatalysis, organic photovoltaics, spectroelectrochemistry and sensing, and as a support for cell biology studies. Although ITO surfaces exhibit heterogeneous local electrical conductivity, little is known as to how this translates to electrochemistry at...
Article
The aim of this paper is to describe the scientific journey taken to arrive at present-day nanoelectrochemistry and consider how the area might develop in the future, particularly in light of papers presented at this Faraday Discussion. By adopting a generational approach, this brief contribution traces the story of the nanoelectrochemistry family...
Article
The electronic structure of an electrode can affect the electron transfer rate of electrochemical processes at its surface. Now, it has been shown that varying the ‘twist’ angle between two stacked layers of graphene modifies the bilayer electronic structure and provides a new dimension to control interfacial redox activity.
Article
Surface charge density and distribution play an important role in almost all interfacial processes, influencing, for example, adsorption, colloidal stability, functional material activity, electrochemical processes, corrosion, nanoparticle toxicity, and cellular processes such as signaling, absorption, and adhesion. Understanding the heterogeneity...
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The surface processes that control crystal growth from solution can be probed in real-time by in situ microscopy. However, when mass transport (partly) limits growth, the interfacial solution conditions are difficult to determine, precluding quantitative measurement. Here, we demonstrate the use of a thermodynamic feature of crystal surfaces-the cr...
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We describe the combination of scanning electrochemical cell microscopy (SECCM) and interference reflection microscopy (IRM) to produce a compelling technique for the study of interfacial processes and to track the...
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2D electrode materials are often deployed on conductive supports for electrochemistry and there is a great need to understand fundamental electrochemical processes in this electrode configuration. Here, an integrated experimental-theoretical approach is used to resolve the key electronic interactions in outer-sphere electron transfer (OS-ET), a cor...
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Nanopipettes are finding increasing use as nano “test tubes”, with reactions triggered through application of an electrochemical potential between electrodes in the nanopipette and a bathing solution (bath). Key to this application is an understanding of how the applied potential induces mixing of the reagents from the nanopipette and the bath. Her...
Article
The setup for operando measurement of hydrogen evolution under illumination is shown in the cover feature picture. Various cobaloxime catalysts were deposited onto solid support (carbon nanomembranes) and evaluated with respect to their hydrogen evolution reaction by using Pd microsensors. The structure of the most efficient cobalt‐based double sal...
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Full-text available
Cobaloximes are promising, earth‐abundant catalysts for the light‐driven hydrogen evolution reaction. Typically, these cobalt(III) complexes are prepared in situ or employed in their neutral form, e.g. [Co(dmgH 2 )(py)Cl], even though related complex salts have been reported previously and could in principle offer improved catalytic activity as wel...
Preprint
Full-text available
In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This “intrinsic proton conductivity” of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene i...
Preprint
In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This “intrinsic proton conductivity” of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene i...
Article
Understanding the formation and properties of the solid‐electrolyte interphase (SEI) will enable the development of enhanced Li‐ion batteries (LiBs) and other battery types. Herein, we report scanning electrochemical cell microscopy (SECCM) in a glovebox to characterize the SEI formation on the basal surface of highly oriented pyrolytic graphite (H...
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Full-text available
Scanning ion conductance microscopy (SICM) is a powerful and versatile technique that allows an increasingly wide range of interfacial properties and processes to be studied. SICM employs a nanopipette tip that contains electrolyte solution and a quasi-reference counter electrode (QRCE), to which a potential is applied with respect to a QRCE in a b...
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Full-text available
Graphite and related sp ² carbons are ubiquitous electrode materials with particular promise for use in e.g., energy storage and desalination devices, but very little is known about the properties of...
Preprint
Full-text available
In 2014, it was reported that hydrated protons are able to traverse nominally pristine monolayer graphene (and hexagonal boron nitride, h-BN) films under ambient conditions. This “intrinsic proton conductivity” of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is impermeable to atoms, ions a...
Preprint
In 2014, it was reported that hydrated protons are able to traverse nominally pristine monolayer graphene (and hexagonal boron nitride, h-BN) films under ambient conditions. This “intrinsic proton conductivity” of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is impermeable to atoms, ions a...
Article
Full-text available
Understanding how the bulk structure of a material affects catalysis on its surface is critical to the development of actionable catalyst design principles. Bulk defects have been shown to affect electrocatalytic materials that are important for energy conversion systems, but the structural origins of these effects have not been fully elucidated. H...
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An artificial synapse is developed that mimics ultramicroelectrode (UME) amperometric detection of single cell exocytosis. It comprises the nanopipette of a scanning ion conductance microscope (SICM), which delivers rapid pulses of neurotransmitter (dopamine) locally and on demand at >1000 defined locations of a carbon fiber (CF) UME in each experi...
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Transition metal (oxy)hydroxides are promising electrocatalysts for the oxygen evolution reaction1–3. The properties of these materials evolve dynamically and heterogeneously⁴ with applied voltage through ion insertion redox reactions, converting materials that are inactive under open circuit conditions into active electrocatalysts during operation...
Preprint
Full-text available
Graphite is a ubiquitous electrode material with particular promise for use in e.g., energy storage and desalination devices, but very little is known about the properties of the graphite-electrolyte double layer at technologically relevant concentrations. Here, the (electrified) graphite-NaCl(aq) interface was examined using constant chemical pote...
Preprint
div> Outer-sphere electron transfer (OS-ET) is a cornerstone elementary electrochemical reaction, yet microscopic understanding is largely based on idealized theories, developed in isolation from experiments that themselves are often close to the kinetic (diffusion) limit. Focusing on graphene as-grown on a copper substrate as a model 2D material/...
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Metabolic analysis in animals is usually either evaluated as whole-body measurements or in isolated tissue samples. To reveal tissue specificities in vivo, this study uses scanning electrochemical microscopy (SECM) to provide localized oxygen consumption rates (OCRs) in different regions of single adult Caenorhabditis elegans individuals. This is a...
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Practically important metal electrodes are usually polycrystalline, comprising surface grains of many different crystallographic orientations, as well as grain boundaries. In this study, scanning electrochemical cell microscopy (SECCM) is applied in tandem with co-located electron backscattered diffraction (EBSD) to give a holistic view of the rela...
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This paper reports on the use of scanning ion conductance microscopy (SICM) to locally map the ionic properties and charge environment of two live bacterial strains: the Gram-negative Escherichia coli and the Gram-positive Bacillus subtilis. SICM results find heterogeneities across the bacterial surface and significant differences among the Gram-po...
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Full-text available
Calcium carbonate (CaCO3) is one of the most well-studied and abundant natural materials on Earth. Crystallisation of CaCO3 is often observed to proceed via an amorphous calcium carbonate (ACC) phase, as a precursor to more stable crystalline polymorphs such as vaterite and calcite. Despite its importance, the kinetics of ACC formation have proved...
Article
Thin-film electrodes, produced by coating a conductive support with a thin layer (nanometer to micrometer) of active material, retain the unique properties of nanomaterials (e.g., activity, surface area, conductivity, etc.) while being economically scalable, making them highly desirable as electrocatalysts. Despite the ever-increasing methods of th...
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Full-text available
High pressure high temperature (HPHT) synthesis of crystallographically well-defined boron doped diamond (BDD) microparticles, suitable for electrochemical applications and using the lowest P and T (5.5 GPa and 1200 C) growth conditions to date, is reported. This is aided through the use of a metal (Fe eNi) carbide forming catalyst and an aluminum...
Preprint
Full-text available
This paper reports on the use of scanning ion conductance microscopy (SICM) to locally map the ionic properties and charge environment of two live bacterial strains: the gramnegative Escherichia coli and the gram-positive Bacillus subtilis . SICM results find heterogeneities across the bacterial surface, and significant differences among the grampo...
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Full-text available
Electrochemical impedance spectroscopy (EIS) is a versatile tool for electrochemistry, particularly when applied locally to reveal the properties and dynamics of heterogeneous interfaces. A new method to generate local electrochemical impedance spectra is outlined, by applying an AC bias between a quasi-reference counter electrode (QRCE) placed in...
Preprint
p>High pressure high temperature (HPHT) synthesis of crystallographically well-defined boron doped diamond (BDD) microparticles, suitable for electrochemical applications and using the lowest P and T (5.5 GPa and 1200°C) growth conditions to date, is reported. This is aided through the use of a metal (Fe-Ni) carbide forming catalyst and an aluminum...
Article
Full-text available
Achieving control over the size distribution of metal organic framework (MOF) nanoparticles is key to biomedical applications and seeding techniques. Electrochemical control over the nanoparticle synthesis of the MOF, HKUST‐1, is achieved using a nanopipette injection method to locally mix Cu 2+ salt precursor and benzene tricarboxylate (BTC 3‐ ) l...
Article
Achieving control over the size distribution of metal organic framework (MOF) nanoparticles is key to biomedical applications and seeding techniques. Electrochemical control over the nanoparticle synthesis of the MOF, HKUST‐1, is achieved using a nanopipette injection method to locally mix Cu 2+ salt precursor and benzene tricarboxylate (BTC 3‐ ) l...
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Full-text available
Many applications in modern electrochemistry, notably electrosynthesis and energy storage/conversion take advantage of the “tunable” physicochemical properties (e.g., proton availability and/or electrochemical stability) of non-aqueous (e.g., aprotic) electrolyte media. This work develops general guidelines pertaining to the use of scanning electro...
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The last five decades of molecular and systems biology research have provided unprecedented insights into the molecular and genetic basis of many cellular processes. Despite these insights, however, it is arguable that there is still only limited predictive understanding of cell behaviours. In particular, the basis of heterogeneity in single-cell b...
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Scanning electrochemical cell microscopy (SECCM) is a robust and versatile scanning electrochemical probe microscopy technique that allows direct correlation of structure-activity at the nanoscale. SECCM utilizes a mobile droplet cell to investigate and visualize electrochemical activity at interfaces with high spatio-temporal resolution, while als...
Article
Single walled carbon nanotube (SWNT) network electrodes, in which a planar arrangement of SWNTs on an inert surface serves as a working electrode for voltammetry, offer considerable attributes for electroanalysis. Here, the effect of SWNT network density on the trace voltammetric analysis of a water-soluble ferrocene derivative (FcCOOH) is investig...
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Full-text available
The ease by which hydrogen is absorbed into a metal can be either advantageous or deleterious, depending on the material and application in question. For instance, in metals such as palladium (Pd), rapid absorption kinetics are seen as a beneficial property for hydrogen purification and storage applications, whereas the contrary is true for structu...
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Scanning electrochemical cell microscopy (SECCM) is used to map anodic and cathodic processes on polycrystalline zinc in 10 mM H 2 SO 4 , at the nanoscale. Electrochemical maps are correlated directly with structural data from electron backscatter diffraction applied to the same regions of the surface, and density functional theory (DFT) calculatio...
Article
The requirement to separate topographical effects from surface electrochemistry information is a major limitation of scanning electrochemical microscopy (SECM). With many applications of SECM involving the study of (semi)conducting electrode surfaces, the hybridisation of SECM with scanning tunnelling microscopy (STM) or a surface conductance probe...
Article
Conductive polymers are exceptionally promising for modular electrochemical applications including chemical sensors, bioelectronics, redox-flow batteries, and photo-electrochemical systems due to considerable synthetic tunability and ease of processing. Despite well-established structural heterogeneity in these systems, conventional macroscopic ele...
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As part of the revolution in electrochemical nanoscience, there is growing interest in using electrochemistry to create nanostructured materials, and to assess properties at the nanoscale. Herein, we present a platform that combines scanning electrochemical cell microscopy with ex-situ scanning transmission electron microscopy, to allow the ready c...
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The properties of steels and other alloys are often tailored to suit specific applications through the manipulation of microstructure (e.g., grain structure). Such microscopic heterogeneities are also known to modulate corrosion susceptibility/resistance, but the exact dependency remains unclear, largely due to the challenge of probing and correlat...
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To fully elucidate the structural controls on corrosion-related processes at metal surfaces, experimental measurements should correlate and compare directly structure and activity at the scale of surface heterogeneities (e.g., individual grains, grain boundaries, inclusions etc.). For example, the hydrogen evolution reaction (HER), which usually se...
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Screen-printed carbon electrodes (SPCEs) are widely used for electrochemical sensors. However, little is known about their electrochemical behavior at the microscopic level. In this work, we use voltammetric scanning electrochemical cell microscopy (SECCM), with dual-channel probes, to determine the microscopic factors governing the electrochemical...
Article
The electrochemical properties of boron doped diamond (BDD) electrodes are strongly influenced by the boron doping level and presence of sp2 carbon impurities. In this study, the impact of highly localised sp2 carbon concentrated at the edge of a BDD electrode, arising from laser cutting during fabrication and exposed during electrode polishing, on...
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Full-text available
Scanning electrochemical cell microscopy (SECCM) has been applied for nanoscale (electro)activity mapping in a range of electrochemical systems, but so far has almost exclusively been performed in controlled-potential (amperometric/voltammetric) modes. Herein, we consider the use of SECCM operated in a controlled-current (galvanostatic or chronopot...
Article
The surface charge and topography of human hair are visualized synchronously at the nanoscale using scanning ion conductance microscopy (SICM), a scanning nanopipette probe technique that uses local ion conductance currents to image the physicochemical properties of interfaces. Combining SICM data with finite element method (FEM) simulations that s...
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Full-text available
The redox activity (Li‐ion intercalation/deintercalation) of a series of individual LiMn2O4 particles of known geometry and (nano)structure, within an array, is determined using a correlative electrochemical microscopy strategy. Cyclic voltammetry (current voltage curve, I‐E) and galvanostatic charge/discharge (voltage time curve, E‐t) is applied a...
Article
The redox activity (Li‐ion intercalation/deintercalation) of a series of individual LiMn2O4 particles of known geometry and (nano)structure, within an array, is determined using a correlative electrochemical microscopy strategy. Cyclic voltammetry (current voltage curve, I‐E) and galvanostatic charge/discharge (voltage time curve, E‐t) is applied a...