Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO2 nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO2 surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye–TiO2 interface is the encapsulation of the dye/TiO2 assembly in an amino-group-containing polyallylamine layer anchored to TiO2. A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H2 evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.