Paul Christensen - Academia.edu (original) (raw)
Papers by Paul Christensen
Plasma Sources Science and Technology, 2015
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License New... more This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License Newcastle University ePrints-eprint.ncl.ac.uk Al-Abduly A, Christensen PA. An in situ and downstream study of nonthermal plasma chemistry in an air fed dielectric barrier discharge (DBD).
Chemical Communications, 1996
Inter-micellar interaction is measured under defined hydrodynamic conditions using a rotating dis... more Inter-micellar interaction is measured under defined hydrodynamic conditions using a rotating disk electrode (RDE).
The Journal of Physical Chemistry C
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License New... more This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License Newcastle University ePrints-eprint.ncl.ac.uk Christensen PA, Jones SWM. An in Situ FTIR Study of Ethanol Oxidation at Polycrystalline Platinum in 0.1 M KOH at 25 and 50 degrees C.
An in-situ FTIR spectroscopic study of the electrochemical oxidation of ethanol at a Pb-modified ... more An in-situ FTIR spectroscopic study of the electrochemical oxidation of ethanol at a Pb-modified polycrystalline Pt electrode immersed in aqueous KOH.
Energy & Environmental Science
There is a growing demand for lithium-ion batteries (LIBs) for electric transportation and to sup... more There is a growing demand for lithium-ion batteries (LIBs) for electric transportation and to support the application of renewable energies by auxiliary energy storage systems. This surge in demand requires...
Nature
Range of recycling technologies Recycling Complexity of process 'Mixing' of materials streams Amo... more Range of recycling technologies Recycling Complexity of process 'Mixing' of materials streams Amount of materials recovered Value of materials recovered Fig. 1 | The waste management hierarchy and range of recycling options. The waste management hierarchy is a concept that was developed from the Council Directive 75/442/EEC of 15 July 1975 (https://eur-lex.europa.eu/legal-content/ EN/TXT/?uri=CELEX%3A31975L0442) on waste by the Dutch politician Ad Lansink, in 1979, who presented to the Dutch parliament a simple schematic representation that has been termed 'Lansink's Ladder', ranking waste management options from the most to least environmentally desirable options. Here, that hierarchy is expanded to consider the range of battery recycling technologies. 'Prevention' means that LIBs are designed to use less-critical materials (high economic importance, but at risk of short supply) and that electric vehicles should be lighter and have smaller batteries. 'Re-use' means that electric-vehicle batteries should have a second use. 'Recycling' means that batteries should be recycled, recovering as much material as possible and preserving any structural value and quality (for example, preventing contamination). 'Recovery' means using some battery materials as energy for processes such as fuel for pyrometallurgy. Finally, 'disposal' means that no value is recovered and the waste goes to landfill.
Plasma Chemistry and Plasma Processing
This paper reports the appraisal of two in situ Fourier Transform InfraRed plasma cells with resp... more This paper reports the appraisal of two in situ Fourier Transform InfraRed plasma cells with respect to the interrogation of the glow of a non-thermal plasma (using a transmission cell), and the non-thermal plasma/solid (i.e. dielectric/catalyst) interface (with a reflectance cell). The paper also reports, for the first time, a direct comparison of the IR spectroscopy of plasmaand thermally-driven chemistry. The system chosen for study was the reduction of CO 2 as there is a wealth of data in the literature for comparison. The catalyst was Macor, a ceramic material comprising primarily Al, Si and Mg oxides. In both the thermal and plasma experiments, rotationally-excited CO 2 (CO Ã 2) was observed: in the plasma system, rotationally-excited CO (CO*) was produced via the reduction of CO 2. Using the transmission cell, the conversion of CO 2 to CO was estimated and found to be up to 9% at energy efficiencies of ca. 1-2%, in line with the literature. No reaction of CO 2 was observed in the thermal system. The data obtained using the reflectance cell were similar to those obtained with the transmission cell, with the minor differences reflecting the longer residence time and higher specific input energy. Interestingly, two plasma-induced bands were observed in the reflectance experiments which increased in intensity with time and input power: these may be due transverse and longitudinal optical modes of SiO 2 and did not appear to participate in the observed chemistry. Keywords Non-thermal plasma Á In situ FTIR spectroscopy Á Reflectance Á Transmission Á CO 2 reduction Electronic supplementary material The online version of this article (
Physical Chemistry Chemical Physics
Nanoparticulate SnO2 produced by a hydrothermal method was characterised by BET, XRD, TGA-MS and ... more Nanoparticulate SnO2 produced by a hydrothermal method was characterised by BET, XRD, TGA-MS and in situ variable temperature diffuse reflectance infra red spectroscopy (DRIFTS) to determine the surface behaviour of water.
Plasma Chemistry and Plasma Processing
In situ Fourier Transform Infra Red spectroscopy was employed to study the plasma glow region of ... more In situ Fourier Transform Infra Red spectroscopy was employed to study the plasma glow region of a non-thermal plasma between two Macor dielectrics and fed with CO 2 , CH 4 and N 2. CO, HCN and formaldehyde were produced and rapidly attained steadystate conditions. In addition, the chain oxides C 5 O 2 and ketene were observed (the first time such species have been seen in the dry reforming of methane) and a liquid film was produced comprising multiple components, one of which was acetamide. The data were interpreted in terms of catalysis by the Macor dielectric and a wholly novel, multizone model in which the liquid film plays a direct and important role. The data obtained in the plasma experiments were compared to an analogous, thermal experiment. Importantly, the results from this work could have major implications across the fields of catalysis, synthesis and origin-of-life chemistry. Keywords Non-thermal plasma Á Ketene Á CO 2 Á Conversion Á Catalysis Á Infrared spectroscopy Á Acetamide Á C 5 O 2
Physical chemistry chemical physics : PCCP, Jan 4, 2018
This paper reports the application of in situ reflectance Fourier Transform InfraRed spectroscopy... more This paper reports the application of in situ reflectance Fourier Transform InfraRed spectroscopy to the study of the thermal and plasma driven reaction of IsoPropyl Alcohol (IPA) at SnO2-coated Macor, the latter a ceramic material comprised of the oxides of Al, Mg and Si. The data so obtained were compared to those obtained using uncoated Macor. When uncoated Macor was employed, no reaction of the IPA was observed up to 600 °C in the thermal experiments, whereas a number of products were observed in the plasma-driven experiments. The results obtained using coated Macor were somewhat different, with no reaction taking place in the plasma-driven experiments, whilst significant reaction took place in the thermally-driven process. In the latter experiments, the chemistry was observed to show four distinct temperature regions, with electron injection into the conduction band of the SnO2 playing a significant role, culminating in the production of CO2. The data were interpreted in terms ...
The journal of physical chemistry. A, Jan 17, 2018
This paper reports in-situ Fourier Transform Infra Red (FTIR) spectroscopic studies on the non-th... more This paper reports in-situ Fourier Transform Infra Red (FTIR) spectroscopic studies on the non-thermal plasma reaction of isopropyl alcohol in dinitrogen at Macor (a ceramic containing oxides of Al, Mg and Si) and the analogous thermally-driven process. Whilst isopropyl alcohol did not react at the Macor at temperatures up to 600°C, the study of the non-thermal plasma-driven process at the ceramic led to unexpected chemistry hitherto not observed, primarily the reaction of IPA in dinitrogen at short timescales to produce methane, HCN, acetone and "cold" CO at ca. 115K. The CO, methane and HCN rapidly established steady state concentrations, pointing to the need for faster FTIR studies: at longer times, isophorone and a "polymethylacetylene-like" polymer were formed as a brown oil. The observation of the steady-state gases and brown oil suggested parallel pathways in the plasma, the latter taking place at the plasma/catalyst interface, and the former in the plasma...
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
ABSTRACT The experimental problems inherent in in-situ SNIFTIRS-type electrochemical experiments ... more ABSTRACT The experimental problems inherent in in-situ SNIFTIRS-type electrochemical experiments are reviewed, and a detailed description of the modifications necessary to a modern commercial FTIR spectrometer that enable it to function in the SNIFTIRS mode are described. Some results are presented to show the sensitivity achievable.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
J. Chem. Soc., Faraday Trans.
ABSTRACT We have used in situ FTIR spectroscopy to examine the effect of incorporating redox-acti... more ABSTRACT We have used in situ FTIR spectroscopy to examine the effect of incorporating redox-active pendant [Ni(tetraazamacrocycle)]2+ moieties in poly(3-methylthiophene)(PMT). Experiments were performed on Pt electrodes modified with PMT, and PMT-copoly-{1-[2-(3-thienyl)ethyl]-1,4,8,11-tetraazacyclotetradecane}nicke(II) perchlorate (PMT–P1) in acetonitrile–0.2 mol l–1 tetraethylammonium tetrafluoroborate. Inspection of the IR activated vibration (IRAV) region of the spectrum (1000–1600 cm–1) of PMT shows that oxidation occurs with three distinct regions of behaviour with increasing potential. There is a changeover in the carrier type being generated between the first two regions, probably from polaron to bipolaron. The evolution of the electronic band (1600–6000 cm–1), due to a charge carrier transition, suggests a relatively uniform conjugation length in this polymer. That the copolymer backbone posesses mobile charges is shown by the observation of IRAVs in its spectra, at similar energies to those observed for other thiophene-based polymers. However, the electronic band of the copolymer is at lower energy than for PMT, and its position changes significantly with potential. This is related to the increase in static relative permittivity of PMT–P1 compared with PMT owing to the ion content of the neutral copolymer film. Neutral PMT films appear to contain very little solvent, whereas neutral PMT–P1 films contain significant quantities, possibly associated with the [Ni(macrocycle)]2+ moieties.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
The Journal of Physical Chemistry C
This paper reports a systematic study of the co-doping of SnO 2 with Sb and Ni in order to identi... more This paper reports a systematic study of the co-doping of SnO 2 with Sb and Ni in order to identify the mechanism responsible for the electrocatalytic generation of ozone on Ni/Sb-SnO 2. Based on interpretation of a combination of X-ray diffraction, BET surface area measurements (N 2) and thermal analysis, the formation of ozone appears to take place on particle surfaces of composite Sb-SnO 2 grains, and is controlled by diffusion of OH along internal crystallite surfaces within the grain. Sb-doped SnO 2 is inactive with respect to ozone evolution in the absence of Ni, demonstrating a synergic interaction between nickel and antimony. From XPS investigations, Sb(V) ions substitute for Sn(IV) in the lattice, with a preference for centrosymmetric coordination sites whilst the Sb(III) ions occur at grain surfaces or boundaries. Ni was not detected by XPS being located in the subsurface region at concentrations below the detection limit of the instrument. In addition to identifying a possible mechanism for ozone formation, the study resulted in the production of active nanopowders which will allow the fabrication of high surface-area anodes with the potential to exceed the space-time yields of β-PbO 2 anodes, permitting the application the Ni/Sb-SnO 2 anodes in the treatment of real waters.
Materials Science and Technology
ABSTRACT The CO2 generated by UV irradiation of unplasticised PVC pigmented with TiO2 was monitor... more ABSTRACT The CO2 generated by UV irradiation of unplasticised PVC pigmented with TiO2 was monitored by in situ Fourier transform infrared (FTIR) spectrometry. CO2 was evolved immediately irradiation began (although no HCl was detected) and when irradiation ceased CO2 evolution fell significantly. A comparison of photogeneration of CO2 from unpigmented and pigmented PVC demonstrated that, although a heavily coated TiO2 (R5) did not increase the rate of CO2 formation, lightly coated TiO2 (R3) photocatalysed PVC oxidation to CO2. As expected for a photocatalytic process, the photogeneration of CO2 increased with increased TiO2 loading. The convenience of the FTIR method allowed the increased rate of oxidation with increasing partial pressure of oxygen, or increasing humidity, to be demonstrated. It was also shown that the rate of photocatalytic oxidation varied as the square root of UV intensity. This dependence would result if recombination of UV generated charge carriers controls the rate of photocatalysis.
Plasma Sources Science and Technology, 2015
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License New... more This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License Newcastle University ePrints-eprint.ncl.ac.uk Al-Abduly A, Christensen PA. An in situ and downstream study of nonthermal plasma chemistry in an air fed dielectric barrier discharge (DBD).
Chemical Communications, 1996
Inter-micellar interaction is measured under defined hydrodynamic conditions using a rotating dis... more Inter-micellar interaction is measured under defined hydrodynamic conditions using a rotating disk electrode (RDE).
The Journal of Physical Chemistry C
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License New... more This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License Newcastle University ePrints-eprint.ncl.ac.uk Christensen PA, Jones SWM. An in Situ FTIR Study of Ethanol Oxidation at Polycrystalline Platinum in 0.1 M KOH at 25 and 50 degrees C.
An in-situ FTIR spectroscopic study of the electrochemical oxidation of ethanol at a Pb-modified ... more An in-situ FTIR spectroscopic study of the electrochemical oxidation of ethanol at a Pb-modified polycrystalline Pt electrode immersed in aqueous KOH.
Energy & Environmental Science
There is a growing demand for lithium-ion batteries (LIBs) for electric transportation and to sup... more There is a growing demand for lithium-ion batteries (LIBs) for electric transportation and to support the application of renewable energies by auxiliary energy storage systems. This surge in demand requires...
Nature
Range of recycling technologies Recycling Complexity of process 'Mixing' of materials streams Amo... more Range of recycling technologies Recycling Complexity of process 'Mixing' of materials streams Amount of materials recovered Value of materials recovered Fig. 1 | The waste management hierarchy and range of recycling options. The waste management hierarchy is a concept that was developed from the Council Directive 75/442/EEC of 15 July 1975 (https://eur-lex.europa.eu/legal-content/ EN/TXT/?uri=CELEX%3A31975L0442) on waste by the Dutch politician Ad Lansink, in 1979, who presented to the Dutch parliament a simple schematic representation that has been termed 'Lansink's Ladder', ranking waste management options from the most to least environmentally desirable options. Here, that hierarchy is expanded to consider the range of battery recycling technologies. 'Prevention' means that LIBs are designed to use less-critical materials (high economic importance, but at risk of short supply) and that electric vehicles should be lighter and have smaller batteries. 'Re-use' means that electric-vehicle batteries should have a second use. 'Recycling' means that batteries should be recycled, recovering as much material as possible and preserving any structural value and quality (for example, preventing contamination). 'Recovery' means using some battery materials as energy for processes such as fuel for pyrometallurgy. Finally, 'disposal' means that no value is recovered and the waste goes to landfill.
Plasma Chemistry and Plasma Processing
This paper reports the appraisal of two in situ Fourier Transform InfraRed plasma cells with resp... more This paper reports the appraisal of two in situ Fourier Transform InfraRed plasma cells with respect to the interrogation of the glow of a non-thermal plasma (using a transmission cell), and the non-thermal plasma/solid (i.e. dielectric/catalyst) interface (with a reflectance cell). The paper also reports, for the first time, a direct comparison of the IR spectroscopy of plasmaand thermally-driven chemistry. The system chosen for study was the reduction of CO 2 as there is a wealth of data in the literature for comparison. The catalyst was Macor, a ceramic material comprising primarily Al, Si and Mg oxides. In both the thermal and plasma experiments, rotationally-excited CO 2 (CO Ã 2) was observed: in the plasma system, rotationally-excited CO (CO*) was produced via the reduction of CO 2. Using the transmission cell, the conversion of CO 2 to CO was estimated and found to be up to 9% at energy efficiencies of ca. 1-2%, in line with the literature. No reaction of CO 2 was observed in the thermal system. The data obtained using the reflectance cell were similar to those obtained with the transmission cell, with the minor differences reflecting the longer residence time and higher specific input energy. Interestingly, two plasma-induced bands were observed in the reflectance experiments which increased in intensity with time and input power: these may be due transverse and longitudinal optical modes of SiO 2 and did not appear to participate in the observed chemistry. Keywords Non-thermal plasma Á In situ FTIR spectroscopy Á Reflectance Á Transmission Á CO 2 reduction Electronic supplementary material The online version of this article (
Physical Chemistry Chemical Physics
Nanoparticulate SnO2 produced by a hydrothermal method was characterised by BET, XRD, TGA-MS and ... more Nanoparticulate SnO2 produced by a hydrothermal method was characterised by BET, XRD, TGA-MS and in situ variable temperature diffuse reflectance infra red spectroscopy (DRIFTS) to determine the surface behaviour of water.
Plasma Chemistry and Plasma Processing
In situ Fourier Transform Infra Red spectroscopy was employed to study the plasma glow region of ... more In situ Fourier Transform Infra Red spectroscopy was employed to study the plasma glow region of a non-thermal plasma between two Macor dielectrics and fed with CO 2 , CH 4 and N 2. CO, HCN and formaldehyde were produced and rapidly attained steadystate conditions. In addition, the chain oxides C 5 O 2 and ketene were observed (the first time such species have been seen in the dry reforming of methane) and a liquid film was produced comprising multiple components, one of which was acetamide. The data were interpreted in terms of catalysis by the Macor dielectric and a wholly novel, multizone model in which the liquid film plays a direct and important role. The data obtained in the plasma experiments were compared to an analogous, thermal experiment. Importantly, the results from this work could have major implications across the fields of catalysis, synthesis and origin-of-life chemistry. Keywords Non-thermal plasma Á Ketene Á CO 2 Á Conversion Á Catalysis Á Infrared spectroscopy Á Acetamide Á C 5 O 2
Physical chemistry chemical physics : PCCP, Jan 4, 2018
This paper reports the application of in situ reflectance Fourier Transform InfraRed spectroscopy... more This paper reports the application of in situ reflectance Fourier Transform InfraRed spectroscopy to the study of the thermal and plasma driven reaction of IsoPropyl Alcohol (IPA) at SnO2-coated Macor, the latter a ceramic material comprised of the oxides of Al, Mg and Si. The data so obtained were compared to those obtained using uncoated Macor. When uncoated Macor was employed, no reaction of the IPA was observed up to 600 °C in the thermal experiments, whereas a number of products were observed in the plasma-driven experiments. The results obtained using coated Macor were somewhat different, with no reaction taking place in the plasma-driven experiments, whilst significant reaction took place in the thermally-driven process. In the latter experiments, the chemistry was observed to show four distinct temperature regions, with electron injection into the conduction band of the SnO2 playing a significant role, culminating in the production of CO2. The data were interpreted in terms ...
The journal of physical chemistry. A, Jan 17, 2018
This paper reports in-situ Fourier Transform Infra Red (FTIR) spectroscopic studies on the non-th... more This paper reports in-situ Fourier Transform Infra Red (FTIR) spectroscopic studies on the non-thermal plasma reaction of isopropyl alcohol in dinitrogen at Macor (a ceramic containing oxides of Al, Mg and Si) and the analogous thermally-driven process. Whilst isopropyl alcohol did not react at the Macor at temperatures up to 600°C, the study of the non-thermal plasma-driven process at the ceramic led to unexpected chemistry hitherto not observed, primarily the reaction of IPA in dinitrogen at short timescales to produce methane, HCN, acetone and "cold" CO at ca. 115K. The CO, methane and HCN rapidly established steady state concentrations, pointing to the need for faster FTIR studies: at longer times, isophorone and a "polymethylacetylene-like" polymer were formed as a brown oil. The observation of the steady-state gases and brown oil suggested parallel pathways in the plasma, the latter taking place at the plasma/catalyst interface, and the former in the plasma...
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
ABSTRACT The experimental problems inherent in in-situ SNIFTIRS-type electrochemical experiments ... more ABSTRACT The experimental problems inherent in in-situ SNIFTIRS-type electrochemical experiments are reviewed, and a detailed description of the modifications necessary to a modern commercial FTIR spectrometer that enable it to function in the SNIFTIRS mode are described. Some results are presented to show the sensitivity achievable.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
J. Chem. Soc., Faraday Trans.
ABSTRACT We have used in situ FTIR spectroscopy to examine the effect of incorporating redox-acti... more ABSTRACT We have used in situ FTIR spectroscopy to examine the effect of incorporating redox-active pendant [Ni(tetraazamacrocycle)]2+ moieties in poly(3-methylthiophene)(PMT). Experiments were performed on Pt electrodes modified with PMT, and PMT-copoly-{1-[2-(3-thienyl)ethyl]-1,4,8,11-tetraazacyclotetradecane}nicke(II) perchlorate (PMT–P1) in acetonitrile–0.2 mol l–1 tetraethylammonium tetrafluoroborate. Inspection of the IR activated vibration (IRAV) region of the spectrum (1000–1600 cm–1) of PMT shows that oxidation occurs with three distinct regions of behaviour with increasing potential. There is a changeover in the carrier type being generated between the first two regions, probably from polaron to bipolaron. The evolution of the electronic band (1600–6000 cm–1), due to a charge carrier transition, suggests a relatively uniform conjugation length in this polymer. That the copolymer backbone posesses mobile charges is shown by the observation of IRAVs in its spectra, at similar energies to those observed for other thiophene-based polymers. However, the electronic band of the copolymer is at lower energy than for PMT, and its position changes significantly with potential. This is related to the increase in static relative permittivity of PMT–P1 compared with PMT owing to the ion content of the neutral copolymer film. Neutral PMT films appear to contain very little solvent, whereas neutral PMT–P1 films contain significant quantities, possibly associated with the [Ni(macrocycle)]2+ moieties.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
The Journal of Physical Chemistry C
This paper reports a systematic study of the co-doping of SnO 2 with Sb and Ni in order to identi... more This paper reports a systematic study of the co-doping of SnO 2 with Sb and Ni in order to identify the mechanism responsible for the electrocatalytic generation of ozone on Ni/Sb-SnO 2. Based on interpretation of a combination of X-ray diffraction, BET surface area measurements (N 2) and thermal analysis, the formation of ozone appears to take place on particle surfaces of composite Sb-SnO 2 grains, and is controlled by diffusion of OH along internal crystallite surfaces within the grain. Sb-doped SnO 2 is inactive with respect to ozone evolution in the absence of Ni, demonstrating a synergic interaction between nickel and antimony. From XPS investigations, Sb(V) ions substitute for Sn(IV) in the lattice, with a preference for centrosymmetric coordination sites whilst the Sb(III) ions occur at grain surfaces or boundaries. Ni was not detected by XPS being located in the subsurface region at concentrations below the detection limit of the instrument. In addition to identifying a possible mechanism for ozone formation, the study resulted in the production of active nanopowders which will allow the fabrication of high surface-area anodes with the potential to exceed the space-time yields of β-PbO 2 anodes, permitting the application the Ni/Sb-SnO 2 anodes in the treatment of real waters.
Materials Science and Technology
ABSTRACT The CO2 generated by UV irradiation of unplasticised PVC pigmented with TiO2 was monitor... more ABSTRACT The CO2 generated by UV irradiation of unplasticised PVC pigmented with TiO2 was monitored by in situ Fourier transform infrared (FTIR) spectrometry. CO2 was evolved immediately irradiation began (although no HCl was detected) and when irradiation ceased CO2 evolution fell significantly. A comparison of photogeneration of CO2 from unpigmented and pigmented PVC demonstrated that, although a heavily coated TiO2 (R5) did not increase the rate of CO2 formation, lightly coated TiO2 (R3) photocatalysed PVC oxidation to CO2. As expected for a photocatalytic process, the photogeneration of CO2 increased with increased TiO2 loading. The convenience of the FTIR method allowed the increased rate of oxidation with increasing partial pressure of oxygen, or increasing humidity, to be demonstrated. It was also shown that the rate of photocatalytic oxidation varied as the square root of UV intensity. This dependence would result if recombination of UV generated charge carriers controls the rate of photocatalysis.