Transition metal-doped titania inverse opals: Fabrication and characterization

Interconversion of inverse opals of electrically conducting doped titanium oxides and nitrides

There is a need for conducting, porous, and chemically stable materials for technologies including, but not limited to, fuel cells, solar cells, and batteries. The need for catalyst support materials that are more durable than carbon black in fuel cells motivated previous studies of the synthesis, characterization, and corrosion resistance of Ti(0.7) W(0.3) O(2) nanoparticles. However, because even higher porosity and increased electrical conductivity are desired, processes were developed to prepare rutile phase Ti(0.7) W(0.3) O(2) and cubic Ti(0.7) W(0.3) N in inverse opal morphologies from a precursor inverse opal of very poorly conducting, amorphous Ti(0.7) W(0.3) O(2.3) . Inverse opals have been explored for a variety of applications from catalysis to photonics, and inverse opals of both oxides and nitrides have been reported. By synthesizing highly conducting mixed-metal oxides and mixed-metal nitrides, the applications of inverse opals can be broadened. Herein, the synthesis and characterization of polystyrene-templated, single-phase, crystalline inverse opals of Ti(0.7) W(0.3) O(2) are reported. These conducting inverse opals can subsequently be converted to inverse opals of Ti(0.7) W(0.3) N and then fully oxidized back to inverse opals of the original insulating, amorphous Ti(0.7) W(0.3) O(2.3) . Such changes in composition and crystal structure, while successfully retaining the inverse opal morphology without the use of a supporting template during the conversion, have not been previously reported.