Systematic Study of Promoting Effects in Titania-Based Systems for Hydrogen Production in Photoreforming Reactions

There is a pressing need in society to begin to move away from fossil fuels as our main source of
energy due to the production of CO2 caused by their combustion. One promising alternative energy
vector is hydrogen, which burns cleanly in fuel cells, producing only water as a byproduct. Yet,
currently more than 95% of hydrogen is produced through steam reforming fossil fuels in a process
which releases significant amounts of carbon dioxide. A promising alternative to this process is
photoreforming of biomass (i.e. glycerol and glucose) to produce hydrogen and CO2 in a net carbon
neutral cycle which uses only the energy from the sun. TiO2 (titania) is a potential photocatalyst for
this process, but it has issues due to the fast recombination of electron-hole pairs after excitation.
Studies have shown that depositing different metal (i.e. Pd, Pt, Au) nanocrystals on the TiO2 helps
prevent recombination by serving as electron sinks and thus increases catalytic efficiency. In this
study, we used palladium nanocrystals as a co-catalyst with the titania. To further reduce
recombination, we also deposited different metal oxides (MnOx, NiOx, CoOx) to act as hole
collectors and thus promoting agents for the oxidative reaction in order to minimize recombination.
Our results demonstrated a decrease in catalytic activity throughout various deposition techniques
leading us to conclude that the metal oxide co-catalysts were detrimental to catalytic activity at the
concentrations tested (3-10 wt%), possibly due to obstruction of the TiO2’s active surface area.

Naccarella, Ian Andrew. (2017). Systematic Study of Promoting Effects in Titania-Based Systems for
Hydrogen Production in Photoreforming Reactions. Stanford Digital Repository. Available at: https://purl.stanford.edu/zb971pv8455