Redox-Driven Processes for Environmental and Energy Applications

QC 2026-10-14

Abstract

The increasing demand for sustainable technologies to addressenvironmental pollution and energy challenges has intensified the interest inredox-driven processes. Controlling oxidation and reduction reaction throughcatalyst design and reaction environment is crucial to address critical challengesrelated to water pollution and enable the production of renewable fuels andchemicals. This thesis investigates the development of electrochemical andphotocatalytic systems for water treatment and energy production, with aparticular focus on catalyst design and surface modification, reaction selectivityand mechanistic understanding.For water treatment applications, carbon-based electrodes were modifiedto improve the electrochemical production of chlorine oxyanions. Platinumnanoparticles were deposited on the carbon electrode using the polyol methodwile fluorine atoms were introduced by electrochemical fluorination method.Both treatments enhanced chlorine evolution activity leading to higher chlorateyields and current efficiencies while reducing cell voltage. Strategies to suppressside reaction on the cathode were also investigated to minimize the use ofhazardous additives such as hexavalent chromium. In addition, otherelectrochemical systems based on activated carbon cloth were evaluated for theremoval of per- and poly-fluoroalkyl substances (PFAS), demonstrating thecombine contribution of electrosorption and electrooxidation processes forpollutant removal. In parallel, nitrogen-doped TiO₂ decorated with cobaltPrussian blue analogue was developed for photo-Fenton degradation ofmicroplastics. This catalyst promoted oxidative degradation under visible-lightirradiation, resulting in microplastic oxidation, surface deterioration, andfragmentation while avoiding the formation of iron sludge commonly associatedwith conventional Fenton systems.For energy production applications two main approaches are studied inthis thesis. First, biomass-assisted photocatalytic hydrogen generation wasinvestigated using different cellulosic materials as a sacrificial agent to improvecharge separation and hydrogen evolution, where platinum loading and pH of thesystem played a main role in the system stability by preventing agglomeration ofiithe sacrificial agent and further precipitation. In addition, Electrochemical nitratereduction was explored as a sustainable path for ammonia production and nitrateremediation. CuFe-based catalyst exhibited enhance nitrate conversion andammonia production, while the use of nickel foam as substrate reduced nitriteformation and energy consumption. To improve overall stability of membranefreedevice working under neutral media conditions, cobalt phosphide (CoP/Ti)anodes were developed, providing stable oxygen evolution activity andcontributing to improved overall device efficiency. Mechanistic studies combiningdistribution of relaxation times (DRT) analysis and density functional theory(DFT) calculations revealed the complementary catalytic roles of Cu, Fe, and CoPduring nitrate reduction and oxygen evolution reactions. Furthermore,hierarchical P(Ni,Co,Fe) nanoarrays demonstrated excellent oxygen evolutionperformance in alkaline media due to their large electrochemical surface area,improved charge-transfer properties, and enhanced catalytic stability.In summary, rational catalyst design and surface engineering can greatly improvethe performance of redox-based systems. The results from this research havemade a substantial contribution toward developing sustainable processes forwater purification, pollutant degradation, production of renewable fuels, andelectrochemical energy conversion systems

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