Transition Metal Oxide Materials for Electrocatalytic and Photocatalytic Water Splitting

• Author / Creator

  Bau, Jeremy A

• As the developing world industrializes, humanity needs to produce a greater fraction of its energy via renewable resources in order to alleviate the scarcity of fossil fuels as well as environmental damage from the exhaust of these fuels. However, renewable sources of energy tend to be intermittent in nature and therefore require a method to store generated energy for use at a later time. Hydrogen gas is a promising potential fuel because it can be produced from water with oxygen gas as a byproduct, resulting in an environmentally-friendly production-consumption cycle with water as the product upon combustion. This thesis presents two different approaches to hydrogen generation from water – using light and electricity – with earth-abundant metal oxide catalysts.
  A dual-semiconductor photocatalyst consisting of α-Fe2O3 and CuFe2O4 semiconductor materials in close contact was prepared by first templating iron oxide precursors on sugarcane leaf followed by functionalization of the resulting α-Fe2O3 surface with copper nanoparticles and high-temperature annealing. Nanoparticle catalysts were further loaded onto the surface of the combined α-Fe2O3/CuFe2O4 heterostructure. Investigation of the CuFe2O4 material revealed that it was a poor semiconductor that could evolve hydrogen independently but at low rates.
  A novel nickel-iron oxide phase with rock-salt structure was synthesized via thermal decomposition of mixed nickel and iron oleate complexes. Despite the natural instability of bivalent iron in rock-salt crystal structures, the single-crystal [Ni,Fe]O nanoparticles were stable even under ambient conditions for long periods of time, even upon thermal treatment at 200 °C. Shape control of the nanoparticles could be achieved via modification of the synthetic conditions, resulting in a variety of shapes including cubes, stars, and spheres. The composition of the nanoparticles could also be controlled yielding a wide composition range of nickel iron oxide rock-salt nanocrystals. The surface of the nanoparticles was determined to contain trivalent iron and an amorphous structure unique from the bulk.
  The nickel-iron oxide nanoparticles were applied for water oxidation after integration onto tin-doped indium oxide and fluorine-doped tin oxide electrode surfaces. The functionalization was accomplished using UV light irradiation, which resulted in the formation of durable nanoparticle films that withstood the stresses of water oxidation. Electrochemical studies suggested that catalytic activity arose from the surface of the nanoparticles, suggesting that the [Ni,Fe]O phase did not participate in water oxidation. Nonetheless, by giving rise to the catalytic surface layer, [Ni,Fe]O was found to be important for water oxidation as activity was reduced when the phase was lost via heating.

• Subjects / Keywords

  • Water Oxidation
  • Water Splitting
  • Earth-Abundant Catalysts

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R35X25J54

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.