A conventional exhaust gas after treatment system (EATS) for the Euro VI legislation contains four different catalyst. The first two (particulate filter system) remove particulates and the last two (SCR system) remove nitrogen oxides (NOx). The particulate filter system also optimizes the gas composition with respect to nitrogen monoxide (NO) and nitrogen dioxide (NO2). The performance of the SCR system has a strong dependency on the NO:NO2 ratio as the so called selective catalytic reduction (SCR) reaction is kinetically favored at a NO:NO2 ratio of 1:1. The diesel oxidation catalyst (DOC) is placed first in the EATS. Due to this placement, the DOC is subjected to a rough environment, e.g. high temperatures and oil/fuel impurities that with time will affect its performance, i.e. the catalyst ages. In this master thesis, the aging of the DOC has been empirically correlated to thermal load and sulfur exposure. The study shows that it is possible to predict how the NO oxidation performance decays as a function of thermal and sulfur exposure. The empirical relation was fitted against two aging cycles and validated against an additional four. The results show that the loss of catalytic activity can to a large extent be explained by the cycle it has been used on. / Ett konventionellt efterbehandlingssystem för Euro VI-standarden innehåller fyra olika katalysatorer. De första två rensar (partikelfiltersystemet) från partiklar och de två sista (SCR-systemet) tar bort kväveoxider (NOx). Partikelfiltersystemet reglerar även gassammansättningen med avseende på kvävemonoxid (NO) och kvävedioxid (NO2). Prestandan för SCR-systemet har ett starkt beroende på NO:NO2-förhållandet där ett förhållande på 1:1 är kinetiskt gynnat för den så kallade SCR-reaktionen (eng: Selective Catalytic Reduction). Oxidationskatalysatorn (DOC) sitter som ett första steg i efterbehandlingen. Placeringen medför att katalysatorn finns i en tuff miljö där den till exempel utsätts för hög temperatur och olje/bränsleföroreningar som över tiden påverkar dess prestanda. Detta brukar kallas att DOC:n åldras. I detta examensarbete har åldrandet av DOC:n korrelerats empiriskt till termisk belastning och svavelexponering. Studien visar att det är möjligt att förutsäga hur NO-oxidationsprestandan avtar som en funktion av termisk last och svavelexponering. Det empiriska modellen anpassades till två åldringscykler och validerades emot ytterligare fyra cykler. Resultaten visar att den kvarvarande katalytiska aktiviteten i stor utsträckning kan förklaras genom vilken cykel den har körts på.

<p>The NOx conversion efficiency of a combined Selective Catalytic Reduction and</p> <p>Ammonia Slip Catalyst (SCR-ASC) in a Diesel Aftertreatment (AT) system degrades with</p> <p>time. A novel model-informed data-driven On-Board Diagnostic (OBD) binary classification</p> <p>strategy is proposed in this paper to distinguish an End of Useful Life (EUL) SCR-ASC catalyst</p> <p>from Degreened (DG) ones. An optimized supervised machine learning model was used for the</p> <p>classification with a calibrated single-cell 3-state Continuous Stirred Tank Reactor (CSTR)</p> <p>observer used for state estimation. The method resulted in 87.5% classification accuracy when</p> <p>tested on 8 day-files from 4 trucks (2 day-files per truck; 1 DG and 1 EUL) operating in realworld on-road conditions.</p>

<p dir="ltr">Catalyzing a green hydrogen economy can accelerate progress towards achieving the goal of a sustainable energy map with net-zero carbon emissions by rapid strides. An environmentally benign electrochemical energy conversion system is the Polymer Electrolyte Fuel Cell (PEFC) which uses hydrogen as a fuel to produce electricity and is notably used in a variety of markets such as industries, commercial setups, and across the transportation sector, and is gaining prominence for use in heavy-duty vehicles such as buses and trucks. Despite its potential, the commercialization of PEFCs needs to address several challenges which are manifested in the form of mass transport limitations and deleterious mechanisms at the interfacial scale under severe operating conditions. Achieving a robust electrochemical performance in this context is predicated on desired interactions at the triple-phase boundary of the electrochemical engine of the PEFC – the porous cathode catalyst layer (CCL) where the principal oxygen reduction reaction (ORR) takes place. The liquid water produced as a byproduct of the ORR helps minimize membrane dehydration; however, excess water renders the reaction sites inactive causing reactant starvation. In addition, the oxidation of the carbonaceous support in the electrode and loss of valuable electrochemically active surface area (ECSA) pose major barriers that need to be overcome to ameliorate the life expectancy of the PEFC.</p><p dir="ltr">In this thesis, the multimodal physicochemical interactions occurring inside the catalyst layer are investigated through a synergistic blend of visualization and computational techniques. The spatiotemporal dynamics of capillary force-driven liquid transport that ensues concentration polarization thereby affecting the desired response will be probed in detail. The drop in efficacy of the ORR due to competing catalyst aging mechanisms and the impact of degradation stressors on chemical potential-induced instability will be examined. The reaction-transport-mechanics interplay in core-shell nanoparticles, a robust class of electrocatalysts that promises better mass activity compared to the single metal counterparts is further highlighted. Finally, the influence of electrode microstructural attributes on the electrochemical performance of the reverse mode of fuel cell operation, i.e., Proton Exchange Membrane Water Electrolyzers (PEMWEs) is investigated through a mesoscale lens.</p>