Abstract The photocatalytic production of hydrogen gas from water–methanol mixtures was performed in contact with a suspended mixture of powdered titanium dioxide (TiO 2) and graphite silica (GS), a naturally available mineral. A drastic synergy effect for hydrogen production was found for GS in collaboration with TiO 2. The amount of hydrogen gas evolved from water–methanol mixtures was increased by a factor of ca. 100 simply by mixing GS with TiO 2. The synergy effect is attributed to the enrichment of hydrogen ions in the clay components of GS and aggregation of GS and TiO 2 particles.