Design and Optimization of Electrocatalysts for Energy Applications

Abstract

In the early 19th century the industrial revolution manifests a paradigm modification in primary energy sources. Energy is obligatory for all modem conveniences and necessities, from transportation, heating, and electricity, to the production of goods, food, and all industrial aspects. With the growing population and modernization, the world's over-all final energy consumption has reached to an alarming situation. Earlier, mankind was mostly relying for energy on firewood burning and analogous biofuels, but with the advent in industrialization, there was a need to move on towards the use of fossil fuels. In the beginning, coal was employed as a source of fuel, later on, oil and gas utilization had played a central role in driving the advancement oftoday's civilizations. In 1973, annual energy demand was 4661 Mtoe (Millions of tons of oil equivalent), raised to 9425 Mtoe in 2014. Meanwhile, renewables such as wind and solar energy have their own limitations depending on the natural geographical distribution and intensity fluctuation. Hence, energy storage and conversion got a significant interest in the worldwide community because it is very operative in both generating power and energy density. The energy conversion has most favorable devices comprises of fuel cells based on the alcohols and water oxidation. They have advantages of better proficiency and zero carbon emission and can be easily used in portable electronic devices and vehicle engines. In the first part ofthis research work, different transition metal (Cr, Mn, Fe, Ni, Cu, and Zn) substituted n-Co(OH)2 materials are synthesized via a simple solution chemistry approach. These materials have delivered superior activities in oxygen evolution reaction displaying high current density at low overpotential. In long term stability, all of them have retained more than 95% capacity for 24 h. The substituted n-Co(OH)2possesses low charge transfer resistance and higher double layer capacitance, both favoring the facile OER kinetics, which is far enhanced than the up-to-dateelectrocatalysts. These novel innovative substituted n-Co(OH)2 have higher surface area due to the presence of interlayer anions which widen up the gap between the layers responsible for their better electrocatalytic properties. In the second part of this research work, metal oxide-based palladium/reduced graphene oxide composites have been synthesized. The synthesized composites were evaluated for the direct liquid fuel cells including methanol, ethanol and formic acid fuel cells. The PdSr/rGO exhibited the best activity generating high current density with low onset potential, because of the large lattice constant of Sr which shifted the Pd d-band centers significantly. The significantly improved activity is due to the high lattice constants of alkaline earth metals and partially due to the higher oxide content which helps in the removal of adsorbed intermediates.