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[Display omitted] • Based on the USPEX screening more stable SiCP 4 allotropes was obtained. • A high carrier mobility of 106 cm2 V−1 s−1 is observed for SiCP 4 allotrope. • The maximum η S T H ′ and η S T F ′ of SiCP 4 allotrope can reach 21.89% and 23.90% • Two SiCP 4 allotropes can trigger HER spontaneously. • SiCP 4 allotropes have the potential to reduce CO 2 to CH 4 or HCOOH. Two-dimensional metal-free photocatalysts are catching the attention of researchers. Here, we present several allotrope SiCP 4 monolayers with high stability, high carrier mobility, and excellent photocatalytic performance. Using a searching method based on the universal structure predictor evolutionary xtallography, together with assessing the energy and thermodynamic stabilities, and matching the potentials of band edges with the photocatalytic conditions for achieving overall water splitting, we successfully identify 5 highly favorable configurations (including the previously reported one) from a pool of 1056 allotrope SiCP 4 monolayers. The results show that the largest solar-to-hydrogen efficiency of the considered monolayers can reach 21.89 %, while a high mobility of 2.7677 × 105 cm2 V−1 s−1 is observed, both are superior to those of the previously reported one. The Gibbs free energies for hydrogen or oxygen evolutions, and CO 2 reduction reactions indicate they are thermodynamically feasible. Moreover, the hydrogen evolution reaction can proceed spontaneously with two allotrope SiCP 4 monolayers. Therefore, the newfound allotrope SiCP 4 monolayers are expected to have potential applications in the field of photocatalytic water splitting for hydrogen generation and carbon dioxide reduction. [ABSTRACT FROM AUTHOR]

The valence of tin is the critical factor affecting the photocatalytic performance of TiO 2 when using tin as dopant. Sn4+ acts as the intermediate step for the electron transfer from Ti4+ to Sn4+ and then to the adjacent Pt, while Sn2+ plays as the defect site for carrier recombination. The intermediate step permit a long carrier lifetime, and enable the electron transfer to the surface adsorbed O 2 to form massive superoxide radical. Function of tin doping, light illumination and Pt loading are clarified. [Display omitted] • The Sn6 achieved a high hydrogen production efficiency of 39.4 mmol·h-1·g-1. • Sn4+ dopingcan promote electron transfer, while Sn2+ doping causes carrier recombination. • The intermediate step on Sn4+ site between Ti4+ and Pt leads to a longer carrier lifetime. • Function of tin doping, light illumination and Pt loading are clarified. Hydrogen production has been considered as the most promising approach for obtaining sustainable and clean energy source. Modification of TiO 2 photocatalyst with the aim of enhancing the photocatalytic efficiency has always been the top importance. In this work, Tin ions have been used as dopant to adjust the crystal phase and to improve the catalytic performance of TiO 2. The results showed that Sn4+ doping transferred the mixed phase TiO 2 photocatalyst into single rutile phase TiO 2 and increased the water splitting efficiency. Photoluminescence, X-ray photoelectron spectroscopy and UV–vis spectrometer characterization suggested that charge transfer between Ti4+ and Sn4+ is the key reason for the suppression of carrier recombination and the improvement of the photocatalytic efficiency. Sn2+ doping did not adjust the rutile/anatase mix phase formation considerably, charge transfer from Ti4+ to Sn4+ is also proved to be the reason for the slightly enhanced water splitting efficiency. This work suggests that the ion valence of tin is the critical factor affecting the photocatalytic performance of TiO 2. [ABSTRACT FROM AUTHOR]