Electrochemical Energy Conversion Catalysts for Water Oxidation and CO2 Reduction

Numerous efforts have been made for the development of renewable energies to replace fossil fuels and thus reduce greenhouse gas emissions. Renewable energy has the advantage of having a limitless supply over time and is clean. This thesis reports on novel transition metal-based electrocatalysts for acidic water splitting and CO2 reduction, which are two significant technologies to produce chemical fuels (i.e. H2 and C-based compounds) from renewable electricity. The target is to develop and investigate cost-effective, stable, and efficient electrocatalysts for acidic water splitting and CO2 reduction, replacing noble metals and achieving performances above the current state of the art. In the first part, the preparation and oxygen evolution properties of the oxygen plasma-treated and acid-activated carbon paper are investigated. This part also presents the Ru incorporated Carbon paper, as an efficient, stable, and self-standing catalyst for OER in acid. This catalyst shows an overpotential of 230 mV vs. RHE at 1 mA cm−2, comparable to the other carbon-based materials. It shows a small Tafel slope of 74 mV dec-1 and 20 hours of stability at 10 mA cm−2. In the second part, the template-assisted wet synthesis and electrochemical OER studies of yolk-shell Co3O4/Co1−xRuxO2 hollow microspheres (MSs) are discussed. It demonstrates a lower overpotential of 240 mV at 10 mA cm-2 and a small Tafel slope of 70 mV dec−1. Also, the MSs exhibit high mass activity of 600 A g−1 and show high stability for 24 hours Chronopotentiometry tests at constant current densities of 10 and 20 mA cm−2 in 0.5 M H2SO4. Finally, nanostructured CdSe/Cu3P/CdSe heterostructures (in the form of nanocoral and sandwiches), obtained through colloidal synthesis, were used as efficient electrocatalysts for CO2 reduction. The nanocoral and Sandwich structured catalyst demonstrated higher CO2-to- HCOO– conversion giving a FEHCOO– of about 60% and 40% at –1.4 V vs RHE, respectively in 0.5 M KCl.