Exponentially self-promoted hydrogen evolution by uni-source photo-thermal synergism in concentrating photocatalysis on co-catalyst-free P25 TiO₂

The concentrating photocatalysis (CPC) to produce hydrogen can be considered as a promising strategy for cooperative utilization of light and heat of full-spectrum solar energy. However, its fundamental mechanism remains elusive and controversial. Here, the P25 TiO₂ photocatalyst, which is optimized kinetically and thermodynamically under 36 × sun irradiation (1 × sun = 1 kW m⁻²), exhibits ultrahigh co-catalyst-free H₂ evolution rate (235.8 μmol h⁻¹), which is 1212 times of that in the conventional photocatalysis (PC) under 1 × sun irradiation as the benchmark. Moreover, hydrogen evolution has been identified to be exponentially correlated to reaction time (throughout the growing and stable temperature stages) and irradiance under Xe lamp and sunlight, respectively. These attractively superlinear characteristics of hydrogen evolution can be attributed to the uni-source photo-thermal synergism of accelerated carrier transfer rate by the high-density heat flux and broadened carrier transfer channel by the high-density photon flux. This work highlights the novel reaction characteristics and mechanisms for enhanced hydrogen evolution in CPC, thus provides new guidance to the performance improvement for conventional PC.