Destabilization of a ligand-stabilized semiconductor nanocrystal solution with
an oxidizing agent can lead to a macroscopic highly porous self-supporting
nanocrystal network entitled hydrogel, with good accessibility to the surface.
The previously reported charge carrier delocalization beyond a single
nanocrystal building block in such gels can extend the charge carrier mobility
and make a photocatalytic reaction more probable. The synthesis of ligandstabilized
nanocrystals with specific physicochemical properties is possible,
thanks to the advances in colloid chemistry made in the last decades. Combining
the properties of these nanocrystals with the advantages of nanocrystalbased
hydrogels will lead to novel materials with optimized photocatalytic
properties. This work demonstrates that CdSe quantum dots, CdS nanorods,
and CdSe/CdS dot-in-rod-shaped nanorods as nanocrystal-based hydrogels
can exhibit a much higher hydrogen production rate compared to their ligandstabilized
nanocrystal solutions. The gel synthesis through controlled destabilization
by ligand oxidation preserves the high surface-to-volume ratio, ensures
the accessible surface area even in hole-trapping solutions and facilitates
photocatalytic hydrogen production without a co-catalyst. Especially with such
self-supporting networks of nanocrystals, the problem of colloidal (in)stability
in photocatalysis is circumvented. X-ray photoelectron spectroscopy and photoelectrochemical
measurements reveal the advantageous properties of the 3D
networks for application in photocatalytic hydrogen production.