  Water splitting through efficient catalysts represents an ultimate solution
for carbon neutrality within 40 years. To achieve this goal, amorphous
photocatalysts are noted for their promising performances. Among them, the best
known is black titania (amorphous TiOx, x < 2). However, despite the large
number of studies on black titania, its color origin, structure-property
relationship, and photocatalytic mechanism remain a topic of hot debate,
largely due to the difficulty to calculate its precise electronic structure.
Here, using ab initio molecular dynamics simulations, we report the precise
electronic structures of black titania and further reveal the generic evolution
pattern of the electronic structures of covalent compounds upon amorphization
and reduction. Moreover, surface adsorption of the co-catalyst atoms (e.g., Pt)
on amorphous substances is simulated for the first time: the disordered surface
enables easy accommodation of the co-catalyst atoms, while the extended
electronic states facilitate the separation of photo-induced electrons and
holes, beneficial for hydrogen evolution. This study elucidates the workings of
amorphous catalysts and offers practical guidance for enhancing their
performances.

Materials Science