Characterizing the ideal structure of an inverse opal copper bismuthate photoelectrode

by Johnson, Anna; Coridan, Robert

The increasing environmental impact of fossil fuel use has sparked interest in the utilization of renewable fuels that can be generated by energy from sunlight. Hydrogen evolution from water electrolysis can be driven by photoelectrochem. cells, though any scalable impact these systems will have on solar-to-hydrogen generation requires that they operate at high power conversion efficiencies and be made from earth-abundant materials. Copper bismuthate, CuBi2 O4 , can be used in photoelectrochem. systems because of the earth abundance of the component elements and a measured bandgap of 1.7 eV. However, carrier collection from CuBi2 O4 photoelectrodes is inhibited by a short minority carrier diffusion length of roughly 40 nm. Here, the potential for CuBi2 O4 inverse opal photocathodes for photoelectrochem. solar-to-hydrogen processes will be characterized by experiment and simulation. The inverse opal motif allows for enhanced light trapping and nanoscale feature sizes that simultaneously improve light absorption and carrier collection. Finite element simulation results will be used to identify favorable design parameters (template structure and electrode thickness) to improve these qualities of an idealized CuBi2 O4 inverse opal photoelectrode. Then, strategies to synthesize inverse opal photoelectrodes by colloid-templated electrodeposition and photoelectrochem. characterization results will be presented. This will include comparisons between simulation results to the incident photon-to-current collection yield in exptl. photocathodes.