Fluorine‐Induced Surface Metallization for Ammonia Synthesis under Photoexcitation up to 1550 nm

Abstract

The first observation of surface metallization of TiO 2Àx induced by fluoride ions is presented. The emerging metallic states are contributed by the 3d orbital of surface Ti and the 2p orbital of surface bridging F, which are intrinsically originated from the strong electron repulsion between F À and adjacent Ti 3+ . The metalized TiO 2Àx with reduced work function and downward band bending possesses high electron-donating power to supported Ru species via atomic-scale ohmic contacts, exhibiting unprecedented photocatalytic performances for ammonia synthesis across the entire solar spectrum region (200-1550 nm) at room temperature. Mechanism and kinetic analysis revealed that the loaded Ru could behave as efficient electron sinks to accumulate photogenerated electrons and that the metallic surface markedly enhanced the dissociation of H 2 and N 2 by the hot electrons generated by the visible or even infrared light irradiation.

Dual Charge-Transfer Channels Harmonize Carrier Separation for Efficient U(VI) Photoreduction

“…As shown in Figure c, the secondary electron cutoff ( E cutoff ) energies on the surfaces of RGO, 1T-MoS 2 , and TiO 2– x were 18.07, 20.71, and 16.65 eV, respectively, while the distances from the top of the valence band to the Fermi energy level were 3.31, 3.28, and 2.08 eV, respectively. According to different work function formulas for metals and semiconductors, the work functions of RGO, 1T-MoS 2 , and TiO 2– x were obtained as 3.15, 3.79, and 4.57 eV, respectively. , When the interfaces of heterojunctions are in contact with each other, electrons are more likely to flow from the side with the smaller work function to the larger one . By simulating the work function of each sample under ideal conditions (Figure S5), it was found that the electron-transfer direction at contact was consistent with the results of the UPS measurements.…”

“…According to different work function formulas for metals and semiconductors, the work functions of RGO, 1T-MoS 2 , and TiO 2−x were obtained as 3.15, 3.79, and 4.57 eV, respectively. 51,52 When the interfaces of heterojunctions are in contact with each other, electrons are more likely to flow from the side with the smaller work function to the larger one. 53 By simulating the work function of each sample under ideal conditions (Figure S5), it was found that the electron-transfer direction at contact was consistent with the results of the UPS measurements.…”

Electronic and Interface Regulation of Wurtzite Surfaces Promotes Photocatalytic Ammonia Synthesis under Visible Light Irradiation

“…As shown in Figure b, the E a of Ru@Ti-ZnO 1– x was 12.3 kJ mol –1 , which was much lower than that of the K/Ru/black TiO 2– x H x photothermal catalyst (65 kJ mol –1 ) and the industrial Haber–Bosch catalyst (about 160 kJ mol –1 ), , confirming that this is a pure photocatalytic process. Moreover, the reaction orders of N 2 and H 2 over Ru@Ti-ZnO 1– x were measured to be only 0.35 and 0.33 (Figure c), respectively, even lower than the values (0.51 and 0.50) of the highly efficient Ru-based F-TiO 2 photocatalyst we recently reported, indicating the enhanced adsorption of N 2 and H 2 on the wurtzite surface of ZnO, resulting in the weak dependencies on the gas-phase reactant concentrations. Due to the upward band bending caused by Ru deposition, the photogenerated holes will tend to migrate to the semiconductor surface and be neutralized by H 2 promptly to form protons (H 2 + 2h + → 2H + ).…”

Recent Progress on Two-Dimensional Materials

“…Considering that most of current photocatalysts with low solar efficiency were excited by ultraviolet light 1169,1170 , rational design of 2D materials with unique optical properties and wide absorption (up to visible or near-infrared light) is prime important to achieve remarkable nitrogen fixation performance. In addition, inspired by thermal catalytic ammonia synthesis, the enriching electron density of surface defects is a key to promote nitrogen activation [1171][1172][1173][1174] . Therefore, the construction of electron-rich structures at the surface of 2D materials in virtue of the confined electron in layered structure may be one of the avenues to high-performance photocatalyst for NRR.…”