Uncovering intrinsic photochemical behaviour changes of semiconductor and synergistic effects in photothermal catalytic H₂ production from water reduction and cellulose pyrolysis

Solar-driven photocatalytic water splitting for hydrogen production is gaining dramatic interests, however, efficiencies are still not satisfied to make it technically applicable in large scale. Herein, we have observed unconventional high-temperature effects on the change of intrinsic photophysical properties of semiconductors, and demonstrated dual synergistic photothermal effects in promoting hydrogen evolution from water reduction and cellulose pyrolysis at high temperature with metal oxides catalysts. Particularly, Zn/ZnO species deposited TiO₂ (Zn-TiO₂) catalyst showcased exceptional thermal-assisted photocatalytic H₂ production from water reduction along with cellulose decomposition at 573 K with quasi apparent quantum efficiency of nearly 100 % under 365±10 nm irradiation and solar to hydrogen (STH) efficiency of 2.72 %. In situ spectroscopic characterizations at 573 K corroborated that the absorption spectrum of Zn-TiO₂ could be extended into the near-infrared region (beyond 1200 nm), and electron-hole pair recombination is curbed and migration of photogenerated charge carriers within the catalyst is remarkably promoted at high temperature. In addition, experimental analysis and molecular dynamics simulations unraveled the synergistic photo-assisted thermal effects for cellulose pyrolysis, and delineated potential pathways for cellulose conversion at high temperature under light irradiation. This work paves the way for efficient utilization of whole solar spectrum for achieving sustainable water splitting and biomass waste utilization.