Nanocatalysts for the electrochemical reduction of carbon dioxide to fuels

This thesis focuses on the synthesis of nanocatalysts for the electroreduction of CO¬2 to useful fuels such as formic acid, methanol, methane and carbon monoxide. Copper-based materials were synthesised via a continuous hydrothermal flow synthesis process (CHFS). This method involved mixing pressurised precursor solutions with supercritical water to rapidly form ultra-fine nanocatalysts. CuO synthesis was investigated by varying experimental parameters, such as mixer types, temperature, pH, metal salt precursor and H¬2O¬2. Particle size was modulated by controlling these parameters and sub-15 nm particle sizes were possible. This has not been previously observed or reported in the literature in flow synthesis for CuO. The as-prepared CuO nanoparticles were formulated into Nafion based inks. The influence of the Nafion fraction on the Faradaic efficiencies and overpotential was explored. The highest Faradaic efficiency for formic acid production (61%) was observed with the optimum Nafion fraction. Insights into the significant increase in the Faradaic efficiency with the optimum Nafion content was elucidated with electrochemical impedance spectroscopy (EIS). Ni doped CuO synthesised via CHFS, was reported here for the first time, where higher inclusion of Ni was possible compared to co-precipitation. The Ni doped CuO samples were evaluated for their electrocatalytic properties and showed higher Faradaic efficiency at lower overpotential (<1.2 V) and below 11 at % Ni, compared to the undoped CuO. The catalysts were evaluated by EIS, Tafel analysis and structural characterisation. Rotating Ring Disk Electrode (RRDE), a hydrodynamic technique, was validated as a high-throughput tool to screen catalysts prior to bulk electrolysis. The Pt ring was successfully used to electrochemically detect formic acid, as it was formed in situ on copper-based catalysts. This was confirmed by conducting product calibration and understanding the oxidation behaviour on Pt as a function of rotation and scan rate

The electrodeposition of tin coatings from deep eutectic solvents and their subsequent whisker growth

Tin electrodeposits produced from aqueous electrolytes are frequently used within the electronics industry due to their high solderability and corrosion protection. One limitation to using these deposits is their spontaneous formation of long conductive filament whiskers. These whiskers grow post-electrodeposition and increase the risk of unwanted electrical shorts within electronic devices. In this thesis, tin electrodeposits produced from a proprietary bright acid Tinmac electrolyte, currently used in industry, were studied. Electrodeposits were produced using a range of current densities with and without agitation and were characterised with respect to crystallographic orientation, topography and surface finish. Moreover, the intermetallic compound (IMC) growth produced at the copper substrate-tin coating interface was assessed over a period of time as its growth is considered to be a significant driving force behind whisker formation. In addition, a technique for the electrochemical anodic oxidation of tin electrodeposits on copper substrates was developed. This technique was used throughout this project for the study of IMC growth from tin electrodeposits as it was able to effectively remove the tin whilst leaving the IMCs and substrate unaffected. Ionic liquids exhibit promising electrochemical characteristics for electrodeposition but are still not widely utilised in industry. Their ability to deposit tin coatings has been studied in the present investigation. Trials concentrated on process optimisation to produce uniform electrodeposits by varying current density, SnCl2.2H2O concentration, and electrolyte composition. These deposits were then characterised and compared to tin coatings of similar thickness produced from Tinmac with respect to topography, surface finish, crystallographic orientation, IMC growth, and whisker propensity. Electrodeposits produced from the ionic liquid electrolyte exhibited a different crystallographic texture, topography, and IMC growth compared to those produced from Tinmac. Moreover, the deposit produced from the ionic liquid featured increased whisker growth compared to those produced from Tinmac, but in a wider context, far less growth than conventional tin electrodeposits in the literature. In addition, by exploiting other electrochemical characteristics of ionic liquids, such as their large potential window, future work may be able to produce novel tin or tin alloy electrodeposits which may further reduce the whisker propensity of deposits produced in this investigation

Fuel cells - A review of government-sponsored research, 1950-1964

Handbook on fuel cell research and technolog

Effect of the air pressure on electro-Fenton process

Electro-Fenton process is considered a very promising tool for the treatment of waste waters contaminated by organic pollutants refractant or toxic for microorganisms used in biological processes [1-6]. In these processes H2O2 is continuously supplied to an acidic aqueous solution contained in an electrolytic cell from the two-electron reduction of oxygen gas, directly injected as pure gas or bubbled air. Due to the poor solubility of O2 in aqueous solutions, two dimensional cheap graphite or carbon felt electrodes give quite slow generation of H2O2, thus resulting in a slow abatement of organics. In this context, we report here a series of studies [7-9] on the effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process. The effect of air pressure, current density, mixing and nature of the organic pollutant was evaluated. [1] E. Brillas, I. Sirés, M.A. Oturan, Chem. Rev., 109 (2009) 6570-6631. [2] C.A. Martínez-Huitle, M.A. Rodrigo, I. Sirés, O. Scialdone, Chem. Rev. 115 (2015) 13362–13407. [3] M. Panizza, G. Cerisola, Chem. Rev. 109 (2009) 6541–6569. [4] I. Sirés, E. Brillas, M.A. Oturan, M.A. Rodrigo, M. Panizza, Environ. Sci. Pollut. Res. 21 (2014) 8336–8367. [5] C.A. Martínez-Huitle, S. Ferro, Chem. Soc. Rev. 35 (2006) 1324–1340. [6] B.P.P. Chaplin, Environ. Sci. Process. Impacts. 16 (2014) 1182–1203. [7] O. Scialdone, A. Galia, C. Gattuso, S. Sabatino, B. Schiavo, Electrochim. Acta, 182 (2015) 775-780. [8] J.F. Pérez, A. Galia, M.A. Rodrigo, J. Llanos, S. Sabatino, C. Sáez, B. Schiavo, O. Scialdone, Electrochim. Acta, 248 (2017) 169-177. [9] A.H. Ltaïef, S. Sabatino, F. Proietto, A. Galia, O. Scialdone, O. 2018, Chemosphere, 202, 111-118

Pressurized CO2 Electrochemical Conversion to Formic Acid: From Theoretical Model to Experimental Results

To curb the severely rising levels of carbon dioxide in the atmosphere, new approaches to capture and utilize this greenhouse gas are currently being investigated. In the last few years, many researches have focused on the electrochemical conversion of CO2 to added-value products in aqueous electrolyte solutions. In this backdrop, the pressurized electroreduction of CO2 can be assumed an up-and-coming alternative process for the production of valuable organic chemicals [1-3]. In this work, the process was studied in an undivided cell with tin cathode in order to produce formic acid and develop a theoretical model, predicting the effect of several operative parameters. The model is based on the cathodic conversion of pressurized CO2 to HCOOH and it also accounts for its anodic oxidation. In particular, the electrochemical reduction of CO2 to formic acid was performed in pressurized filter press cell with a continuous recirculation of electrolytic solution (0.9 L) at a tin cathode (9 cm2) for a long time (charge passed 67’000 C). It was shown that it is possible to scale-up the process by maintaining good results in terms of faradaic efficiency and generating significantly high concentrations of HCOOH (about 0.4 M) [4]. It was also demonstrated that, for pressurized systems, the process is under the mixed kinetic control of mass transfer of CO2 and the reduction of adsorbed CO2 (described by the Langmuir equation), following our proposed reaction mechanism [5]. Moreover, the theoretical model is in good agreement with the experimental results collected and well describes the effect of several operating parameters, including current density, pressure, and the type of reactor used. 1. Ma, S., &amp; Kenis, P. J. (2013). Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges, and future opportunities. Current Opinion in Chemical Engineering, 2(2), 191-199. 2. Endrődi, B., Bencsik, G., Darvas, F., Jones, R., Rajeshwar, K., &amp; Janáky, C. (2017). Continuous-flow electroreduction of carbon dioxide. Progress in Energy and Combustion Science, 62, 133-154. 3. Dufek, E. J., Lister, T. E., Stone, S. G., &amp; McIlwain, M. E. (2012). Operation of a pressurized system for continuous reduction of CO2. Journal of The Electrochemical Society, 159(9), F514-F517. 4. Proietto, F., Schiavo, B., Galia, A., &amp; Scialdone, O. (2018). Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell. Electrochimica Acta, 277, 30-40. 5. Proietto, F., Galia, A., &amp; Scialdone, O. (2019) Electrochemical conversion of CO2 to HCOOH at tin cathode: development of a theoretical model and comparison with experimental results. ChemElectroChem, 6, 162-172

Study of fuel cells using storable rocket propellants Final report, 28 Jan. 1964 - 29 Jan. 1965

Fuel cells using storable rocket propellants for reactant

Interrogating electrocatalytic mechanisms and developing nano-porous catalysts for energy conversion reactions: I. Oxygen evolution reaction, and II. Carbon dioxide reduction reaction

The objectives of my thesis were to interrogate electrocatalytic mechanisms and develop new nano-porous catalysts for energy conversion reactions including the oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CRR). First, I examined the oxygen evolution reaction in basic electrolytes using in situ electrochemical surface stress measurements. Second, I developed a new electrolyte additive-controlled electrodeposition method for the preparation of porous films of Ni and NiFe catalysts with high OER activity. Third, I exploited the additive-controlled electrodeposition method to synthesize Cu and CuAg films with high surface area and tunable morphology for high activity and selectivity of CRR to ethylene. In Chapter 1, I provide background information to the electrochemical energy conversion reaction and lay out the challenges and potential approaches at present in the field. In Chapter 2, I describe our effort to determine the relationship between changes in the OER catalyst surface and activity. In situ electrochemical surface stress measurements were utilized to interrogate oxide formation before and during OER on several common catalysts, including Ir, Ni, Co, Au, and Pt. The stress measurements report directly on changes in oxidation state and phase of the electrode material as the potential is varied. Hysteresis observed in the potential-dependent stress with Ir, Au and Pt electrodes is associated with irreversible composition and roughness changes in the electrode. The stress data also quantitatively reports on the in-plane change in strain developing in bonding during oxide oxidation. The magnitude of the surface stress is nearly identical to that the predicted from bond strains obtained from reported XAS data. Interestingly, there is a rough linear relationship between the change in stress and the amount of oxide formed. More importantly, the stress data shows that metals with higher activity exhibit larger stress and more oxide formation. The origin of this relationship could be explained by differences in conductivity and porosity of different oxides. In Chapter 3, I focus on developing a stable and effective OER catalyst using an additive-controlled electrodeposition. We find that 3,5-diamino-1,2,4-triazole (DAT) acts as a deposition inhibitor that dramatically changes Ni morphology resulting in black Ni films, a phenomenon indicative of small particle formation. Ni films electrodeposited with DAT (NiDAT) exhibit much higher active surface areas with fractal-like behavior. Correspondingly, NiDAT films show a much larger oxidation wave and higher OER rates compared to the Ni film deposited without the DAT additive. Co-electrodeposition of Ni and Fe in the presence of DAT (NiFeDAT) is also explored as Fe is known to increase the OER activity from Ni films. NiFeDAT films are very active toward OER exhibiting 100 mA/cm2 with high stability > 72 hours at 1.50V vs RHE in 1 M NaOH. These metrics make NiFeDAT among the most active OER electrocatalyst reported to date. Equally important, the high activity can be tuned to nearly any arbitrary value by altering the amount of NiFe electrodeposited without film degradation. In Chapter 4, I present electrochemical measurements that examine the effect of deuteration on the OER with Ni and Co catalysts, and an effort to identify the rate-determining step (RDS) of these intricate electrocatalytic reactions involving multiple proton-coupled electron transfer (PCET) processes. The OER Tafel slope and kinetic isotope effect (KIE) calculated from electrochemical data shows that both Ni and Co exhibits inverse secondary KIE, which is never observed before in an electrochemical experiment. These results contribute to a more complete understanding of the OER mechanism and allow for the future development of improved nonprecious-metal catalysts. In Chapter 5, I discuss exploiting the additive-controlled electrodeposition method to synthesize Cu films with high surface area and tunable morphology for high activity and selectivity of CRR to ethylene. Electrodeposition of Cu films from plating baths containing DAT (CuDAT) as an inhibitor exhibit high surface area and high CO2 reduction activities. By changing pH and deposition current density, the morphologies of the Cu films are varied to exhibit wires, dots, or amorphous structures. Among these Cu films, the CuDAT-wire samples exhibit the best CO2 reduction activity with a Faradaic efficiency (FE) of the C2H4 product formation reaching 41% at -0.47 V vs. RHE, a FE for C2H5OH formation reaching 22% at -0.55 V vs. RHE, and a mass activity for CO2 reduction at -0.65V vs. RHE of ~ 720 A/g. In Chapter 6, I present our strategy to enhance C2 production from CO2 electroreduction by doping low Ag contents (<10%) into Cu-wire film. The CuAg-wire catalyst with nanoporous structure and homogenous mixed of Cu and Ag atoms was fabricated by additive-controlled electrodeposition method using DAT. The CuAg-wire catalyst exhibits large active surface and high selectivity of CO2 reduction to C2H4 (~60% Faradaic efficiency - FE) and C2H5OH (~25% FE) at relatively low overpotential (~ -0.7V vs RHE)

40th Rocky Mountain Conference on Analytical Chemistry

Final program, abstracts, and information about the 40th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 25 - August 1, 1998

Book of abstracts of the 10th International Chemical and Biological Engineering Conference: CHEMPOR 2008

This book contains the extended abstracts presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, over 3 days, from the 4th to the 6th of September, 2008. Previous editions took place in Lisboa (1975, 1889, 1998), Braga (1978), Póvoa de Varzim (1981), Coimbra (1985, 2005), Porto (1993), and Aveiro (2001). The conference was jointly organized by the University of Minho, “Ordem dos Engenheiros”, and the IBB - Institute for Biotechnology and Bioengineering with the usual support of the “Sociedade Portuguesa de Química” and, by the first time, of the “Sociedade Portuguesa de Biotecnologia”. Thirty years elapsed since CHEMPOR was held at the University of Minho, organized by T.R. Bott, D. Allen, A. Bridgwater, J.J.B. Romero, L.J.S. Soares and J.D.R.S. Pinheiro. We are fortunate to have Profs. Bott, Soares and Pinheiro in the Honor Committee of this 10th edition, under the high Patronage of his Excellency the President of the Portuguese Republic, Prof. Aníbal Cavaco Silva. The opening ceremony will confer Prof. Bott with a “Long Term Achievement” award acknowledging the important contribution Prof. Bott brought along more than 30 years to the development of the Chemical Engineering science, to the launch of CHEMPOR series and specially to the University of Minho. Prof. Bott’s inaugural lecture will address the importance of effective energy management in processing operations, particularly in the effectiveness of heat recovery and the associated reduction in greenhouse gas emission from combustion processes. The CHEMPOR series traditionally brings together both young and established researchers and end users to discuss recent developments in different areas of Chemical Engineering. The scope of this edition is broadening out by including the Biological Engineering research. One of the major core areas of the conference program is life quality, due to the importance that Chemical and Biological Engineering plays in this area. “Integration of Life Sciences & Engineering” and “Sustainable Process-Product Development through Green Chemistry” are two of the leading themes with papers addressing such important issues. This is complemented with additional leading themes including “Advancing the Chemical and Biological Engineering Fundamentals”, “Multi-Scale and/or Multi-Disciplinary Approach to Process-Product Innovation”, “Systematic Methods and Tools for Managing the Complexity”, and “Educating Chemical and Biological Engineers for Coming Challenges” which define the extended abstracts arrangements along this book. A total of 516 extended abstracts are included in the book, consisting of 7 invited lecturers, 15 keynote, 105 short oral presentations given in 5 parallel sessions, along with 6 slots for viewing 389 poster presentations. Full papers are jointly included in the companion Proceedings in CD-ROM. All papers have been reviewed and we are grateful to the members of scientific and organizing committees for their evaluations. It was an intensive task since 610 submitted abstracts from 45 countries were received. It has been an honor for us to contribute to setting up CHEMPOR 2008 during almost two years. We wish to thank the authors who have contributed to yield a high scientific standard to the program. We are thankful to the sponsors who have contributed decisively to this event. We also extend our gratefulness to all those who, through their dedicated efforts, have assisted us in this task. On behalf of the Scientific and Organizing Committees we wish you that together with an interesting reading, the scientific program and the social moments organized will be memorable for all.Fundação para a Ciência e a Tecnologia (FCT