As glycerol (GLY) has emerged as a highly functional and cheap platform molecule and as an abundant biodiesel production byproduct, possible conversion methods have been investigated. One of the promising approaches is the glycerol electrooxidation (GEOR) on noble metal-based catalysts. Although noble metals, especially Pt, are generally very stable at different pH and highly selective toward three-carbon (C3) products, their electrocatalytic performance can be further improved by morphology tuning and alloying with non-noble metals like Co. In the present study, cubic PtxCo100-x (x = 100, 80, and 60) nanoparticles were investigated in an alkaline medium at 20 and 40 °C. The effect of the composition and reaction conditions on the selectivity of the GEOR toward C3 products like lactate and glycerate was studied, and the reaction mechanism was discussed. The highest mass activity was found for Pt80Co20, although when the specific activity, glycerol conversion, and GEOR selectivity were compared, Pt60Co40 was the superior catalyst overall. In general, all catalysts, even those that are Co-rich, exhibited a high C3 product selectivity up to 95% at 0.67 V vs RHE. The low applied potential of 0.67 V vs RHE at 40 °C facilitated lactate formation with selectivity up to 72%. At the same time, the glycerate formation with a selectivity of up to 40%, as well as C-C bond cleavage, was more favored at 0.87 V vs RHE.

     As the biodiesel industry's growth skyrocketed in the past 20 years, it resulted in the accumulation of its main by-product—glycerol. Despite its extensive applications in the pharmaceutical industry, medicine, cosmetics, agriculture, and food industries, the supply exceeds the demand. Hence, glycerol, being abundant and cheap, has emerged as a promising feedstock for producing value-added chemicals. One of the tactics to generate those products is the glycerol electrooxidation reaction (GEOR), where glycerol is oxidised at the anode and hydrogen gas is generated at the cathode.

In the present thesis, noble metal-based nanoparticles were synthesised, characterised, and evaluated in alkaline media as catalysts for the GEOR. In order to assess and optimise the electrocatalytic performance and selectivity of the GEOR toward three-carbon (C3) products, different parameters like the morphology and composition of the catalyst, exposed crystallographic facets, electrolyte composition and electrolysis potential were studied.

The centre of the attention of the research covered were Pd, Pd-Ni, Pt and Pt-Co nanoparticles with an octahedral, rhombic dodecahedral, and cubic shape and more irregular shapes. Cubic-shaped catalysts with {100} faces were the best-performing among the investigated systems. In addition, alloying of Pd and Pt with non-noble Ni and Co improved the efficiency of the GEOR compared to their noble monometallic counterparts while generally retaining the selectivity of C3 products mostly represented by glycerate and lactate.

Under de senaste 20 åren har tillväxten inom biodieselindustrin skjutit i höjden och resulterat i en ackumulering av dess huvudsakliga biprodukt – glycerol. Trots dess omfattande användning inom läkemedels-, kosmetika-, och livsmedelsindustrin och medicin samt inom jordbruket överstiger utbudet efterfrågan. Därför har glycerol, som är ett rikligt förekommande och billigt ämne, framträtt som en lovande råvara för produktion av värdefulla kemikalier. En av strategierna för att generera dessa produkter är glycerolelektrooxidationsreaktionen (GEOR), där glycerol oxideras vid anoden och vätgas genereras vid katoden.

I den här avhandlingen syntetiserades, karakteriserades och utvärderades nanopartiklar baserade på ädla metaller i alkaliska medier som katalysatorer för GEOR. För att bedöma och optimera den elektrokatalytiska prestandan och selektiviteten hos GEOR gentemot produkter med tre kolatomer (C3), studerades olika parametrar såsom katalysatorernas morfologi, sammansättning, exponerade kristallografiska fasetter, elektrolytsammansättning och elektrolyspotential.

Forskningsfokus låg på Pd, Pd-Ni, Pt och Pt-Co nanopartiklar med oktaedrisk, rombisk dodekaedrisk och kubisk form, samt mer irreguljärt formade dendriter och nanopartiklar. Kubformade katalysatorer med {100} ytor var de bäst presterande. Dessutom förbättrade legering av Pd och Pt med icke-ädelmetallerna Ni och Co effektiviteten hos GEOR jämfört med deras ädla monometalliska motsvarigheter, samtidigt som de i allmänhet behöll selektiviteten för C3-produkter som främst representeras av glycerat och laktat.

Стремительный рост производства биодизеля в течение последних 20 лет привёл к избытку его основного побочного продукта, глицерина, вопреки его широкому применению в фармацевтике, медицине, сельском хозяйстве, косметической и пищевой промышленности. Одним из способов его реализации является валоризация путём реакции электроокисления глицерина (РЭОГ), в ходе которой глицерин окисляется на аноде, а газообразный водород выделяется на катоде.

В ходе выполнения настоящей диссертации были синтезированы и охарактеризованы наночастицы на основе благородных металлов и исследованы их электрокаталитические свойства в РЭОГ в щелочной среде. Для оценки и оптимизации электрокаталитической активности и селективности РЭОГ к трёхуглеродным (C3) продуктам были изучены такие параметры как морфология и состав катализаторов, тип кристаллографических граней, состав электролита и потенциал электролиза.

Объектами исследования были Pd, Pd-Ni, Pt и Pt-Co наночастицы октаэдрической, ромбододекаэдрической и кубической формы, а также дендриты и наночастицы более неправильной формы. Катализаторы кубической формы с {100} гранями имели лучшие характеристики среди изученных систем. Кроме того, легирование Pd и Pt с неблагородными Ni и Co улучшило эффективность РЭОГ по сравнению с их монометаллическими аналогами с сохранением селективности к C3 продуктам, среди которых преобладали глицерат и лактат.

Electrochemical conversion of glycerol offers a promising route to synthesize value-added glycerol oxidation products (GOPs) from an abundant biomass-based resource. While noble metals provide a low overpotential for the glycerol electrooxidation reaction (GEOR) and high selectivity toward three-carbon (C3) GOPs, their efficiency and cost can be improved by incorporating non-noble metals. Here, we introduce an effective strategy to enhance the performance of Pd nanoparticles for the GEOR by alloying them with Ni. The resulting PdNi nanoparticles show a significant increase in both specific activity (by almost 60%) and mass activity (by almost 35%) during the GEOR at 40 °C. Additionally, they exhibit higher resistance to deactivation compared to pure Pd. Analysis of the GOPs reveals that the addition of Ni into Pd does not compromise the selectivity, with glycerate remaining at around 60% of the product fraction and the other major product being lactate at around 30%. Density functional theory calculations confirm the reaction pathways and the basis for the higher activity of PdNi. This study demonstrates a significant increase in the GEOR catalytic performance while maintaining the selectivity for C3 GOPs, using a more cost-effective nanocatalyst.

Glycerol, being an abundant and cheap by-product of biodiesel production, has emerged as a raw material that can be recycled into value-added compounds. In the present study, Pt nanoparticles of cubic (Pt_CUBE) and dendritic (Pt_DEND) morphologies were investigated as catalysts for the glycerol electrooxidation reaction (GEOR) at 20 °C. To optimise the electrocatalytic performance and GEOR selectivity towards three-carbon (C3) products, namely lactate, glycerate, and tartronate, the effects of morphology, electrolyte composition, and applied potential were studied. At low glycerol concentrations, C–C bond cleavage was more favoured, especially on Pt_DEND. Both Pt_CUBE and Pt_DEND showed high C3 product selectivity up to 91% at 0.67 V vs. RHE, with lactate reaching a maximum selectivity of 68% on Pt_CUBE, which also exhibited the best mass and specific activities compared to Pt_DEND.

Glycerol is a renewable chemical that has become widely available and inexpensive due to the increased production of biodiesel. Noble metal materials have shown to be effective catalysts for the production of hydrogen and value-added products through the electrooxidation of glycerol. In this work we develop three platinum systems with distinct pore mesostructures, e.g., hierarchical pores (HP), cubic pores (CP) and linear pores (LP); all with high electrochemically active surface area (ECSA). The ECSA-normalized GEOR catalytic activity of the systems follows HPC > LPC > CPC > commercial Pt/C. Regarding the oxidation products, we observe glyceric acid as the main three-carbon product (3C), with oxalic acids as the main two-carbon oxidation product. DFT-based theoretical calculations support the glyceraldehyde route going through tartronic acid towards oxalic acid and also help understanding why the dihydroxyacetone (DHA) route is active despite the absence of DHA amongst the observed oxidation products.

Pd octahedral, rhombic dodecahedral, and cubic nanoparticles (Pd_OCTA, Pd_RD, and Pd_CUBE NPs) were synthesized, characterized, and studied as catalysts for the glycerol electrooxidation reaction (GEOR) in a strongly alkaline medium at 20 and 60 °C. The highest mass activity of 0.050 and 0.183 mA/μg_Pd was observed on Pd_OCTA at 20 and 60 °C, respectively, whereas Pd_CUBE exhibited the highest specific activity of 1.49 and 12.84 mA/cm_Pd², respectively. The GEOR products were analyzed by high-performance liquid chromatography (HPLC), and their selectivity and overall glycerol conversion were evaluated at 0.86 V vs RHE. The selectivity toward the three-carbon chain (C3) GEOR products was similar for the different types of catalysts, with Pd_OCTA and Pd_CUBE NPs achieving more than 50% selectivity at 20 °C and more than 60% at 60 °C. Glycerate was the overall dominant product for all catalysts, with a selectivity of up to 42%. The glycerol conversion was found to be highest for Pd_OCTA─21% at 20 °C and 82% at 60 °C, while Pd_RD was the least active and showed less than 3% conversion at 20 °C and 35% at 60 °C. Based on the GEOR product distribution, a reaction mechanism was proposed.

Through glycerol electrooxidation, we demonstrate the viability of using a PdNi catalyst electrodeposited on Ni foam to facilitate industrially relevant rates of hydrogen generation while concurrently providing valuable organic chemicals as glycerol oxidation products. This electrocatalyst, in a solution of 2 M NaOH and 1 M glycerol at 80 °C, enabled current densities above 2000 mA cm^-2 (in a voltammetric sweep) to be obtained in atmospheres of both air and N₂. Repeated potential cycling under an aerated atmosphere to these exceptional current densities indicated a high stability of the catalyst. Through steady state polarisation curves, 1000 mA cm^-2 was reached below an anodic potential of 0.8 V vs RHE. Chronoamperometry showed glycerate and lactate being the major oxidation products, with increased selectivity for lactate at the expense of glycerate in aerated systems. Aerated atmospheres were demonstrated to consistently increase the apparent Faradaic efficiency to >100%, as determined by the concentration of oxidation products in solution. The excellent performance of PdNi/Ni in aerated solutions suggests that O₂ removal from the electrolyte is not needed for an industrial glycerol electrooxidation process, and that combining electrochemical and chemical glycerol oxidation, in the presence of dissolved O₂ presents an important process advantage.

A novel method exploiting the in situ reactivation of a PdNi catalyst to enhance the electro-oxidation of alcohols is reported. The periodic regeneration of the catalyst surface leads to significant gains in terms of conversion rate, energy requirements and stability compared to the conventional potentiostatic method.