Synthesis of binary and ternary Pd-based Nanocatalysts for alcohol oxidation in alkaline media for fuel cell application

>Magister Scientiae - MScThis study explores the use of UV-assisted reduction method to synthesise the catalysts, aiming at reducing synthesis time. The Pd and Au catalyst loading is kept at 5 wt% in order to reduce the cost associated with high loading (20 wt%) of platinum group metals. The synthesised catalysts have SnO2 incorporated in them for two purposes, one being to activate the chemical reaction by absorbing UV-light and the second one is to serve as a promoter for binary and ternary catalysts. All the synthesised electrocatalysts in this study were denoted as Au/10wt%SnO2-C, Au/15wt%SnO2-C, Au/20wt%SnO2-C, Au/40wt%SnO2-C, Au/60wt%SnO2-C, Pd/10wt%SnO2-C, Pd/15wt%SnO2-C, Pd/20wt%SnO2-C, Pd/40wt%SnO2-C, Pd/60wt%SnO2-C and PdAu/10wt%SnO2-C respectively. The UV-assisted reduction method was proved to be effective with the obtained results from TEM, SEM, XRD and electrochemical studies. TEM micrographs revealed nanoparticles of Pd, Au and SnO2 which were proved by the measured d-spacing values corresponding to the element’s structures. The measured average particle size ranged from 3.05 to 14.97 nm for the electrocatalysts. The XRD profiles confirmed the face centred cubic of Pd, Au and tetragonal structures of SnO2. These electrocatalysts showed varied activity towards the oxidation of alcohols namely, methanol, ethanol, ethylene glycol and glycerol in alkaline electrolyte The cyclic voltammetry results showed improved performance towards the oxidation of glycerol on Au-based electrocatalysts, highest current density of 22.08 mA cm-2 than on Pd-based electrocatalysts. Pd-based electrocatalysts were more active towards the oxidation of ethanol than Au-based electrocatalysts with the highest current density of 19.96 mA cm-2. The co-reduced PdAu on 10wt%SnO2-C electrocatalysts showed the lowest current density of 6.88 mA cm-2 for ethanol oxidation when compared to Pd/10wt%SnO2-C and Au/10wt%SnO2-C. Linear sweep voltammograms showed more negative onset potentials on Pd-based electrocatalysts than Au-based electrocatalysts. The more negative onset potential obtained on Pd-based electrocatalysts was observed for ethanol oxidation. These results correspond to the trend observed in literature for ethanol oxidation being more favoured on Pd-based electrocatalysts whereas the polyalcohol oxidation is more favoured on Au-based electrocatalysts. The best performing and most stable electrocatalyst among the Au-based electrocatalysts is Au/10wt%SnO2-C and Pd/10wt%SnO2-C for the Pd-based electrocatalysts

Algebraic approaches to artificial chemistries

We have developed a new systematic framework, MetaChemisty for the description of artificial chemistries (AChems). It encompasses existing systems. It has the flexibility and complexity to allow for new features and new systems. A joint description language will allow comparisons to be drawn between systems. This will allow us to write metrics and benchmarks for artificial chemistries. It also enables us to combine existing systems in different ways to give a wealth of more complex and varied systems. We will be able to build novel chemistries quicker through reuse of code and features between chemistries allowing new chemistries to start from a more complex base line.We have also developed an algebraic artificial chemistry, Jordan Algebra Artificial Chemistry (JA AChem). This chemistry is based on existing algebra which is leverage to ensure features such as isomers and isotopes are possible in our system. The existence of isotopes leads naturally to the existence of elements for this chemistry. It is a chemistry with both constructive and destructive reactions making it a good candidate for further study as an open-ended system.We analyse the effect of changing probabilistic processes in JA AChem by modifying the probability spawning functions that control them. We also look at the algebraic properties of these probability spawning functions. We have described Swarm Chemistry, Sayama (2009),in the MetaChem showing it is at least more expressive than the previous framework for artificial chemistries, Dittrich et al. (2001).We use the framework to combine two artificial chemistries using a simple environment link structure to produce eight new modular AChems with a modular approach. This link structure requires minimal addition to existing code for artificial chemistry systems and no modification to most modules