I have made a tungsten oxide material using a templating and calcining method, however under TEM it was found that the tungsten particles were completely covered with amorphous carbon from the template. For the purposes of catalysis it would be preferable to have the tungsten sites exposed, at least partially.
I don't think the carbon growth can be controlled during calcination, but is there a niche way I might remove the carbon layer afterwards? I believe carbon can be etched in highly basic solutions, however tungsten oxide is soluble in base so etching in base probably will not work well.
Have you tried argon sputtering or plasma treatment?
Plasma treatment is a widely used method for removing carbon containing residuals or contaminants from TEM samples. Depending on type of plasma (air, nitrogen, argon,...), power, pressure and time you can treat almost all samples. Tungsten oxide should easily withstand a plasma treatment.
Another idea would be to use a FIB to prepare TEM lamella. Depending on the size of your structures, maybe a cross section could overcome the carbon layer problem.
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