Fossil fuel combustion, responsible for climate change, is driving the development and deployment of renewable energy generation and storage technologies. Intermittent solar photovoltaic and wind generators require energy storage systems to capture and release the energy at appropriate times because supply and demand are not synchronized. Flow batteries and fuel cells combined with water electrolyzers are under development but are relatively expensive which limit their deployment. Cost reductions could be achieved by improving the catalyst performance and durability leading to cuts in unit size and material needs. The Hawaii Natural Energy Institute has partnered with Kyushu University to develop carbide based catalysts and improve performance and durability.
Carbides derived from more abundant transition metals are less expensive than platinum used in proton exchange membrane fuel cells. Carbides have electronic structures resembling platinum and therefore are expected to have a similar activity. Carbides are also highly stable and less susceptible to corrosion than carbon supports for platinum catalysts. Low-cost synthesis techniques for large-scale production of transition metal carbide catalysts will be developed using carbothermal reactions. Two structures will be considered. Both will favor the formation of nano-sized catalyst particles that are strongly adherent to the catalyst support. These features are expected to enhance catalyst activity with a larger exposed surface area and durability by restricting particle coalescence which decreases the exposed surface area. The composition will be tuned for specific reactions. Naturally abundant biomass, a renewable, easily available and low-cost carbon source for the synthesis reactions will be used, such as coconut shell and husk, apricot stone, sugar beet bagasse, cane bagasse, and rice husk. The carbides structure and composition will be investigated by many analytical techniques (X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy). The activity of these carbides will be determined with a rotating ring/disk electrode, a standard electrochemical analysis method, for reactions relevant to fuel cells, water electrolyzers and flow batteries (hydrogen evolution and oxidation, oxygen evolution and reduction, vanadium(III) reduction, vanadium(II) oxidation, vanadium(V) reduction, vanadium(IV) oxidation).
Point Person: Jean St-Pierre
Porous molybdenum carbide (MoCx) nano-octahedrons for the electrocatalytic production of hydrogen (H2) from water (H2O) (left). Field emission scanning electron microscopy image (inset: digital photo) of porous MoCx nano-octahedrons; scale bar, 2 micrometers (right). Courtesy: Nature Communications, volume 6 (2015) article number 6512.