Kalle Kunskap Free
Statens konstråd utvecklar sammanhang där samtidskonst och offentliga rum möts. Statens konstråd producerar permanenta och tillfälliga konstprojekt i offentliga miljöer och engagerar konstnärer i stadsutvecklingsprojekt, samt sprider kunskap och erfarenheter vidare i Sverige och utomlands.
Kalle Kunskap Free
Det övergripande syftet har varit att öka kunskapen om hur socialt utsatta grupper inkluderas i transportplaneringen och hur deras mobilitet och tillgänglighet kan tillgodoses med nya smarta mobilitetskoncept som komplement eller alternativ till konventionell kollektivtrafik.
Pt is one of the most commonly used catalysts for green energy applications, such as fuel cells, electrolyzers, and dye-sensitized solar cells. Although enormous effort has been put into improving the catalytic activity and minimizing the usage of Pt in the catalysts, the low abundance and high price of Pt still limit the large-scale commercialization of green energy devices and facilities. Developing cost-effective and highly efficient Pt-free catalysts is urgent and imperative. γ-radiation induced synthesis approach is known for its mild reaction condition, good controllability, and upscaling production capability. In this thesis, Pt-free nanocatalysts of various types: monometallic (Ni, Ag nanoparticles), bimetallic (Ag-Ni core-shell and heterostructures, Pd-Ni nanoframe, Ni-Co alloys), metal oxides (MnOx, CeO2), and hybrids (Pd-CeO2, Ag-ionomer), are designed and fabricated using γ-radiation induced synthesis method. The structural, chemical and electrocatalytic properties of the obtained nanocatalysts are analyzed.
First, Ni nanoparticles (NPs) were synthesized. It was found that the freestanding Ni NPs are small (3 nm) and tend to agglomerate to larger clusters (Paper I). Based on the results obtained for the Ni NPs, binary nanocatalysts Ni-Co, Ni-Ag, and Ni-Pd are produced. It has been shown for Ni-Co alloy nanoparticles that, by varying the Ni-to-Co ratio, one can tune their electrocatalytic performance for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) (Paper IV). By introducing the less expensive noble metal Ag to the catalysts, bimetallic Ni-Ag NPs with different structures are fabricated: heterostructure (Ag-Ni) and core-shell (Ag@NiO). A comparative study of these two different nanocatalysts allowed us to separate the contributions of ligand and strain effects on the ORR activity of the Ni-Ag catalysts (Paper II). By mixing up the highly active but expensive metal, Pd, with a less expensive transition metal, Ni, Ni-Pd nanocatalysts with a framework (PdNi-NF) and nanochain (PdNi-NC) morphology are obtained. PdNi-NF nanocatalysts deposited on commercial carbon black exhibit superior ORR activity and durability due to their framework morphology and Pd-enriched surface layer (Paper III). Since poly(vinyl alcohol) (PVA) has often been used as a surfactant to control the size of nanoparticles in γ-radiation induced synthesis, it is found that residual PVA on the catalyst surface may inhibit its activity. Therefore, an anion-exchange ionomer is tried to be used as the surfactant, and it turns out to be a superior, efficient size regulator for the synthesis of Ag NPs. The mechanism of Ag particle size control was studied. The prepared Ag NPs covered by the ionomer are applied as model catalysts to investigate the kinetics of ORR (Paper VIII).