Michael E G Lyons

• B.Sc., Ph.D., FTCD
• Head of Department at Trinity College Dublin

The primary goal of this article is to present novel analytical solutions for the coupled nonlinear equation found in the mediated electron transfer process at polymer-modified conducting ultramicroelectrodes. Taylor’s series method is utilized to obtain approximate analytical solutions for the reaction-diffusion equations, allowing for the determi...

An electrochemical photobioreactor with a packed bed containing transparent gel granules and immobilized photosynthetic bacterial cells is shown with a one-dimensional two-phase flow and transport model. We consider the biological/chemical events in the electrochemical photobioreactor, the intrinsically connected two-phase flow and mass transport,...

Identifying the active site of catalysts for the oxygen evolution reaction (OER) is critical for the design of electrode materials that will outperform the current, expensive state-of-the-art catalyst, RuO2. Previous work shows that mixed Mn/Ru oxides show comparable performances in the OER, while reducing reliance on this expensive and scarce Pt-g...

In this paper, Akbari-Ganji's and Taylor series methods are applied to find analytical solutions to nonlinear differential equations that arise in an immobilized-cell photobioreactor. Approximate analytical expressions for substrate and product concentrations and both liquid and gas phases for various parameter values are derived using both methods...

This paper discusses the mathematical modelling of exothermic explosions in a slab. This model is based on a nonlinear equation containing a nonlinear term related to Arrhenius, bimolecular, and sensitised laws of reaction kinetics. The absolute temperature can be obtained by solving the nonlinear equation using Akbari-Ganji’s method. The influence...

Immobilized enzymes are used in many applications in the food industry presently. Some researchers employ apparent kinetic parameters in immobilized enzyme reactor systems, which only apply to these specific case studies. To increase productivity in a packed bed reactor, it is vital to establish a thorough understanding of all the factors affecting...

A theoretical model of an amperometric biosensor with a modified electrode that inhibits the substance is addressed. The solution of a system of reaction-diffusion equations in a bounded region with a non-linear term similar to non-Michaelis- Menten kinetics of the enzymatic reaction is the basis for this model. The estimated analytical expression...

The theoretical model for a packed porous catalytic particle of the slab, cylindrical, and spherical geometries shape in fixed-bed electrochemical reactors is discussed. These particles have internal mass concentration and temperature gradients in endothermic or exothermic reactions. The model is based on a nonlinear reaction–diffusion equation con...

The mathematical model proposed by Chapman and Antano (Electrochimica Acta, 56 (2010), 128–132) for the catalytic electrochemical–chemical (EC’) processes in an irreversible second-order homogeneous reaction in a microelectrode is discussed. The mass-transfer boundary layer neighbouring an electrode can contribute to the electrode’s measured AC imp...

A mathematical model of an ideal biotrickling filter (BF) system that inoculates a recently identified strain of Chelatococcus daeguensis TAD1 and brings about efficient nitrogen oxide treatment is discussed. The proposed model is based on nonlinear mass transport equations at the gas–biofilm interface. Using Akbari–Ganji’s technique, approximate a...

Biosensor behaviour is characterised by non-linear differential equations that describe well-defined physical, chemical, and biological processes. Mathematical modelling of these biosensors is highly desirable since they have many applications. These models enable the prediction of a variety of their properties. In this study, the cyclic conversion...

The steady-state model of an enzyme monolayer adsorbed onto a rotating disc electrode is explored. This model is predicated on a nonlinear system of equations that consists of a nonlinear term related to the reaction rate. A new homotopy perturbation method and Taylor's series approach are employed to derive two efficient and reliable analytical ex...

A theoretical model for the enzyme catalysed isomerisation reaction in a packed-bed reactors made up of microporous particles is discussed. The system is described in terms of finite-range Fickian diffusion and non linear Michaelis-Menten reaction kinetics to produce a non linear reaction/diffusion equation which is solved both numerically by MATLA...

The transient response of amperometric enzyme-based biosensors working in trigger mode is discussed. Nonlinear time-dependent partial differential equations for Michaelis–Menten reaction kinetics are solved analytically using a new approach of homotopy perturbation technique. The simple and closed-form analytical expression for concentration profil...

A theoretical model of amperometric enzyme electrodes has been developed in which chemical amplification occurs in a single enzyme membrane via cyclic substrate conversion. The system is based on non-stationary diffusion equations with a nonlinear factor related to the Michaelis–Menten kinetics of the enzymatic reaction. By solving the nonlinear eq...

The approximate transient chronoamperometric limiting current generated from the electrochemical reaction in a rotating disc electrode for second-order ECE reactions is derived when the chemical step is irreversible. This model is based on nonlinear reaction-diffusion equations containing a nonlinear term related to homogeneous reaction. By solving...

In trigger mode, an amperometric biosensor is a form of a biosensor where the coupling of various enzymes improves the specificity and sensitivity of the detecting event. In this paper, approximate simple analytical expressions have been derived for the substrate and products concentration in the steady-state and transient condition using the well-...

Theoretical models of an amperometric biosensor with product inhibition kinetics are discussed. These models are based on non-stationary diffusion equations containing a non-linear term related to non-Michaelis-Menten kinetics of the enzymatic reaction. The approximate analytical representation of steady-state concentrations is provided for small v...

Diffusion and kinetics of amperometric immobilized enzymes on the planar, cylindrical and spherical electrodes are discussed. This model is described as a set of non-linear reaction-diffusion equations consisting of a non-linear term related to Michaelis-Menten kinetics and enzyme-catalyzed reactions. In this paper, we obtain approximately the gene...

In this paper, we describe the problem of describing the transport and catalytic kinetics at immobilized enzymes in an electronically conductive polymer thin film where substrate inhibition is important. Here, the enzyme kinetics are not well described by the Michaelis-Menten equation. We describe a mathematical procedure based on the recently deve...

In this paper which is dedicated to Professor Richard Compton for his 65th birthday, we examine the problem of describing the transport and kinetics of catalytic reactions in which the catalyst is immobilized within a support matrix such as for example redox enzymes immobilized in a polymer matrix, to form a chemically modified electrode. We examin...

Direct alcohol fuel cells are highly promising as efficient power sources for various mobile and portable applications. However, for the further advancement of fuel cell technology it is necessary to develop new, cost-effective Pt-free electrocatalysts that could provide efficient alcohol oxidation and also resist cross-over poisoning. Here, we rep...

Fuel cells have a number of benefits over conventional combustion-based technologies and can be used in a range of important applications, including transportation, as well as stationary, portable and emergency backup power systems. One of the major challenges in this field, however lies in controlling catalyst design which is critical for developi...

Identifying cheap, yet effective, oxygen evolution catalysts is critical to the advancement of water splitting. Using liquid exfoliated Co(OH)2 nanosheets as a model system, a simple procedure is developed to maximize the activity of any oxygen evolution reaction nanocatalyst. First the nanosheet edges are confirmed as the active areas by analyzing...

The all-conjugated diblock copolymer poly[9,9-bis(2-ethylhexyl)fluorene]-b-poly[3-(6-trimethylammoniumhexyl) thiophene] bromide (PF2/6-b-P3TMAHT) shows dual fluorescence from the polyfluorene (PF) and polythiophene (PT) blocks. Interaction with a range of nucleotide phosphates, at biologically relevant concentrations, was observed to bring about dr...

Recent developments in the literature of oxygen evolution catalysis are discussed. Issues in experimental testing for catalyst comparison are detailed with particular focus on the use of porous foam supports. Ideas for optimization of the system are given such as increasing electrolyte concentration and film thickness.

Finding alternative routes to access and store energy has become a major issue recently. Transition metal oxides have shown promising behaviour as catalysts and supercapacitors. Recently, liquid exfoliation of bulk metal oxides appears to be an effective route which provides access to 2-dimensional (2D) nano-flakes, the size of which can be easily...

Porous manganese carbonate was obtained via solvothermal synthesis using ethanol and urea. The manganese carbonate was subsequently used as a precursor to synthesise mesoporous manganese oxides via thermal treatments at three various temperatures. X-ray diffraction and Extended X-ray Absorption Fine Structure (EXAFS) results shows that g-MnO 2 is s...

Recent research trends have seen a rise in the interest in Transition Metal Oxides (TMO's) as catalysts for the Oxygen Evolution Reaction (OER). In particular, the use of inexpensive mixed TMO's such as Fe and Ni has gained much attention. While some techniques, such as electrodeposition, are widely investigated, reports into the fabrication of Fe,...

Recent developments in electrochemical water oxidation in aqueous alkaline solution at earth abundant transition metal oxyhydroxide thin film electrodes are outlined and candidate high activity materials identified. The molecular mechanism of oxygen evolution at these oxide surfaces is discussed.

Herein, a thermal decomposition method was utilised to fabricate pure and mixed manganese and ruthenium oxides for catalysts in the Oxygen Evolution Reaction (OER). X-ray Photoelectron spectroscopy (XPS) and X-ray Diffraction (XRD) reveal the manganese and ruthenium species produced at the annealing temperature of 600 C to be Mn2O3 and RuO2/Ru, res...

In this study, nickel oxide films were prepared through an electrodeposition technique. NiO films were fabricated on Indium Tin Oxide (ITO) supports by cycling the potential between two different sets of limits. The electrodeposition technique which involved using the shorter potential limits was denoted as deposition process 1 and the technique us...

A rigorous study of electrodeposited pure and mixed Ni/Fe oxides was performed in three different sodium hydroxide electrolytes with various Fe impurity concentrations (<1 ppb, 5 ppb and 102 ppb). The presence and concentration of the Fe impurities in the three electrolytes is determined by Inductive Coupled Plasma spectroscopy. The rationale for i...

Fundamental aspects of the oxygen evolution reaction mediated by metal oxide catalysts are presented. The oxygen evolution reaction is a critical bottleneck in the generation of hydrogen as a renewable fuel via water-splitting. Accordingly, understanding and optimising the oxygen evolution reaction is a major challenge for renewable energy research...

Mixed Mn/Ru oxide thermally prepared electrodes using different compositions of Mn and Ru precursor salts have been fabricated on Ti supports via thermal decomposition at two annealing temperatures. Subsequently, the oxygen evolution reaction (OER) activities of these electrodes were determined. A majority of the mixed Mn/Ru catalysts are highly ac...

The first example of a uranyl selenocyanate compound is reported. The compound [Et4N]3[UO2(NCSe)5] has been synthesized and fully characterized by vibrational and multinuclear (¹H, ¹³C{¹H} and ⁷⁷Se{¹H}) NMR spectroscopy. The photophysical properties have also been recorded and trends in a series of uranyl pseudohalides discussed. Spectroscopic evid...

The combination of a platinum group material (i.e. ruthenium) with a first row transition metal (i.e. manganese) could provide stability and lower the cost of OER electrocatalyst, while still obtaining good OER properties. In this work classical electrochemical techniques have been used to study the electrocatalytic properties of thermally prepared...

In a typical metal recovery process, where highly purified metals are obtained from a concentrated electrolyte, usually the cathodic electrodes are planar and can be described mainly as bi-dimensional. This leads to a low space-time yield and low normalized space velocity with an impact on production rates. New requirements of low-energy consumptio...

Theoretical models describing transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at RDE surfaces modified with catalytically active layers are presented. Model A regards the interaction between the surface immobilized redox active mediator and substrate being described in terms of bimolecular react...

The cathodic superactivation of gold using a repetitive potential cycling procedure is reported, and its significance for the oxygen evolution reaction is discussed. The superactivated surfaces exhibit a transient oxygen evolution response subsequent to monolayer oxidation and prior to extensive visible oxygen evolution. The kinetics of this oxygen...

Some general considerations pertaining to electrochemical water oxidation at transition metal oxide films are outlined. It is suggested that hydrated surfaquo groups are key species in the oxygen evolution reaction mechanism. The latter connect homogeneous and heterogeneous water oxidation catalysis.

RuO2/NiO mixed oxide electrodes prepared by thermal decomposition were examined as potential water oxidation catalysts. Addition of just 10 mol% RuO2 to a NiO electrode was found to decrease the oxygen evolution reaction (OER) onset potential by 20% with increasing additions having significantly diminishing returns. The OER current densities for th...

The chemisorption of aryldiazonium salts is one of the most versatile reactions for the modification of carbon surfaces; in this work we investigated the spontaneous chemisorption of aryldiazonium salts at amorphous carbons of differing graphitic content in order to relate surface reactivity to the valence electronic properties of aryldiazonium cat...

Various manganese oxide type Dimensionally Stable Anode (DSA) electrodes were prepared though a simple thermal decomposition technique at different annealing temperatures for their effect on the oxygen evolution reaction (OER). Along with the change in different annealing temperatures, the effects of different metal substrates were also explored. C...

The electro-oxidation of glucose at nickel hydroxide films is discussed. These films can be electrodeposited using a simple potential multi-cycling procedure. The resulting films exhibit a nanostructured surface morphology. Cyclic voltammetry, rotating-disk electrode voltammetry and electrochemical impedance spectroscopy have been used to elucidate...

The effect of electrochemically ageing hydrous nickel oxide films via slow repetitive potential multi-cycling across the main nickel (II/III) redox peak was investigated in an aqueous base environment using cyclic voltammetry and steady state polarisation curves in the oxygen evolution reaction (OER) region. Similarities between hydrous nickel oxid...

The RuO2/NiO electrode was found to be extremely effective as a water oxidation catalyst in alkaline conditions. Addition of 25 mol % of RuO2 to a NiO electrode lowered the oxygen evolution reaction (OER) overpotential by ca. 30 %. Based on kinetic data obtained we have proposed a mechanism for both RuO2 and NiO utilizing the surfaquo group concept...

This paper presents a review of the redox and electrocatalytic properties of transition metal oxide electrodes, paying particular attention to the oxygen evolution reaction. Metal oxide materials may be prepared using a variety of methods, resulting in a diverse range of redox and electrocatalytic properties. Here we describe the most common synthe...

The oxygen evolution reaction at multi-cycled iron oxy-hydroxide films in aqueous alkaline solution is discussed. Steady-state Tafel plot analysis and electrochemical impedance spectroscopy have been used to elucidate the kinetics and mechanism of oxygen evolution. Tafel slopes of ca. 60 mV dec(-1) and ca. 120 mV dec(-1) are found at low and high o...

The redox switching reaction and the oxygen evolution reaction at multi-cycled nickel oxy-hydroxide films in aqueous alkaline solution are discussed. The hydrous oxide is considered as a porous assembly of interlinked octahedrally coordinated anionic metal oxyhydroxide surfaquo complexes which form an open network structure. The latter contains con...

Novel Nafion and single-walled carbon nanotube composite hydrous iron oxide electrodes have been fabricated using a simple potential cycling methodology and are examined as oxygen evolution electrocatalyst films. Hydrous oxide materials prepared in this manner are typically quite amorphous in nature. Here, we show, using scanning electron microscop...

An environmentally benign and scalable route for the production of gram scale quantities of nitrogen-doped graphene using a downstream microwave plasma source is reported. Simultaneous reduction and doping of graphene oxide is achieved and the process negates the need for high temperatures and toxic solvents associated with existing methods. This g...

The oxygen evolution reaction at multi-cycled iron oxy-hydroxide films in aqueous alkaline solution is discussed. Steady-state Tafel plot analysis and electrochemical impedance spectroscopy have been used to elucidate the kinetics and mechanism of oxygen evolution. Tafel slopes of ca. 60 mV dec(-1) and 40 mV dec(-1) are found at low overpotentials...

The oxygen evolution reaction atmulti-cycled iron oxy-hydroxide films in aqueous alkaline solution is discussed. The factors affecting the growth and electrocatalytic properties of the latter are described. In particular, steady-state Tafel plot analysis and electrochemical impedance spectroscopy have been used to elucidate the kinetics and mechani...

The chemisorption of aryldiazonium salts is one of the most versatile reactions for the modification of carbon surfaces; in this work we investigated the spontaneous chemisorption of aryldiazonium salts at amorphous carbons of differing graphitic content in order to relate surface reactivity to the valence electronic properties of aryldiazonium cat...

The formation via repetitive potential cycling of a thin nickel oxy-hydroxide film on conductive Au, GC and Pt support surfaces is described. The redox and acid/base behavior and electro-catalytic activity with respect to water oxidation to form molecular oxygen of nickel oxyhydroxide thin films on gold support surfaces in aqueous base are describe...

The redox switching reaction and the oxygen evolution reaction at multi-cycled nickel oxy-hydroxide films in aqueous alkaline solution are discussed. The hydrous oxide is considered as a porous assembly of interlinked octahedrally coordinated anionic metal oxyhydroxide surfaquo complexes which form an open network structure. The latter contains con...

The electro-catalytic activity with respect to water oxidation to form molecular oxygen of iron oxyhydroxide thin films on iron support surfaces in aqueous base is described. A mechanism involving iron surfaquo groups is proposed in excellent agreement with the kinetic data. It is shown that the rate determining step of the oxygen evolution reactio...

Outstanding issues regarding the film formation, the redox switching reaction and the oxygen evolution reaction (OER) electrocatalytic behaviour of multi-cycled nickel oxy-hydroxide films in aqueous alkaline solution have been discussed. The oxide is grown using a repetitive potential multi-cycling technique, and the mechanism of the latter hydrous...

Outstanding issues regarding the film formation, redox switching characteristics and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been revisited. The oxide is grown using a repetitive potential multicycling technique, and the mechanism of the latter hydrous o...

The methodology required to measure the conductivity of single fibres is outlined, the basic underlying physics discussed and recent pertinent examples culled from the scientific literature are presented for illustration. Indications of where the field will progress are presented.

Outstanding issues regarding the film formation and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been revisited. The oxide is grown using a repetitive poltential multicycling technique, and the mechanism of the latter hydrous oxide formation process has been...

The use of hydrogen gas produced by the electrolysis of water is the basis of a long term energy conversion and storage option that has been and still continues to be the subject of considerable research. Alkaline water electrolysis, using electricity generated by renewable sources has been proposed as an environmentally inoffensive route to the pr...

The kinetics and mechanism of the oxygen evolution reaction at a series of RuO(2)/IrO(2) mixed oxides in aqueous acid and alkaline solution has been examined using a variety of electrochemical methods. Factors affecting the electrocatalytic activity have been elucidated and novel oxygen evolution mechanisms in terms of reactive oxyruthenium and oxy...

The use of hydrogen gas produced by the electrolysis of water is the basis of a long term energy conversion and storage option that has been and still continues to be the subject of considerable research. Alkaline water electrolysis, using electricity generated by renewable sources has been proposed as an environmentally inoffensive route to the pr...

The redox behavior of ferrocene alkane thiol self assembled monolayer modified electrodes in contact with aqueous perchlorate solutions both in the absence of and in the presence of an external magnetic field is examined using both electrochemical and gravimetric techniques The redox switching process involves an ET reaction involving the ferrocene...

The redox behaviour of well characterized ferrocene alkane thiol self assembled monolayer modified electrodes in contact with aqueous perchlorate solutions both in the absence of and in the presence of an external magnetic field is examined using both electrochemical and gravimetric techniques The redox switching process has been shown to involve a...

a b s t r a c t Despite the recent renewal in interest in the oxygen evolution reaction (OER) at transition metal oxide based electrodes in alkaline solution, the details of the mechanism remain controversial. While most studies focus on a particular oxide in isolation, a consistent experimental examination of the oxides of adjacent elements is lik...

A mathematical model describing the transport and kinetics of substrate and redox mediator in surface deposited films of finite thickness is described. These bio-catalytically active chemically modified electrodes comprise redox enzymes immobilized in a highly dispersed mesh of single walled carbon nanotubes (SWNT) which are in turn immobilized on...

A closed form analytical expression is derived for the normalized current versus potential response expected for a rotating disc electrode in which an initial fast electron transfer reaction is followed by a homogeneous electrochemical reaction which exhibits second order kinetics. The effect of the homogeneous reaction on the shape of the voltamme...

Due to their small size and remarkable electrical properties, carbon nanotubes have been used to modify electrode surfaces to create sensors for a range of important analytes. In this study, glassy carbon (GC) electrodes modified with films of HiPCo® single-walled carbon nanotubes (SWCNTs) were prepared by drop-coating dispersions of the nanotubes....

Although the mechanism for the oxygen evolution reaction (OER) is likely to be similar for oxidised electrodes of the adjacent transition metals Ni, Co and Fe, the electrochemical impedance spectra, recorded for each of these anodes during oxygen evolution in 1.0M NaOH, are significantly different in appearance. This impedance data is analysed usin...

Outstanding issues regarding the redox switching characteristics and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been examined. Charge percolation through the hydrous layer has been quantified, using cyclic voltammetry, in terms of a charge transport diffusi...

In this review essay some recent approaches to nanotethering and nanowiring of biomolecules such as redox enzymes and nanoparticles to solid surfaces to generate chemically modified electrodes to serve as platforms for bottom up designed nanostructures for use in nanobioelectronics are described.

A mathematical model describing transport and kinetics of substrate and redox mediator within chemically modified electrodes comprising of redox enzymes immobilized in dispersed carbon nanotube meshes dispersed on support electrode surfaces is described. Two modes of amperometric detection are subjected to analysis. In the first the current arising...

Various aspects of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Ni electrodes in aqueous alkaline solution were investigated using electrochemical techniques. Steady state polarisation and electrochemical impedance spectroscopy (EIS) were used to measure kinetically significant parameters including the Tafel slope an...

The kinetics of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Fe electrodes in aqueous alkaline solution were examined using both dc steady state polarisation and ac impedance techniques. It proved difficult to obtain reproducible polarisation data for bright anodes, and so an electrochemical pre-treatment routine was...

Details are outlined of an electrochemical investigation of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Co electrodes in aqueous alkaline solution. Kinetic studies on electrodes subjected to different pre-treatment routines, yielded different values of the Tafel slope and the reaction order with respect to OH -activ...

The redox behaviour of glucose oxidase adsorbed on glassy carbon electrodes which have been modified with a dispersed mesh of single wall carbon nanotubes is probed both qualitatively and quantitatively using cyclic voltammetry and potential step chronoamperometry. We have shown that potential step chronoamperometry is the method of choice when con...

The behaviour of support electrodes modified with randomly dispersed single-wall carbon nanotube meshes containing adsorbed glucose oxidase with respect to amperometric glucose detection at a low potential is demonstrated.

Approaches to the mathematical modelling of biosensor interfaces are examined. The important example of amperometric enzyme electrodes is treated in detail. In particular the solution phase transport and direct electrode kinetics of electroenzymes are described in terms of a simple model in which the steady state reaction/diffusion equation for enz...