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Environmentally friendly catalysts with excellent performance and low cost are critical for photocatalysis. Herein, using hydrogenated TiO 2 (h-TiO 2 ) nanosheets with enriched oxygen vacancies as the support, two-dimensional CoO/h-TiO 2 Z-scheme heterostructures are fabricated for hydrogen production through photocatalytic water splitting. It is revealed that the oxygen vacancies in h-TiO 2 can inhibit the oxidation of Co 2+ into high-valence Co 3+ during the hydrothermal reaction and thermal treatment processes. A CoO/h-TiO 2 Z-scheme heterostructure possesses a space charge region and a built-in electric field at the interface, and oxygen vacancies in h-TiO 2 can provide more reactive sites, which synergistically improve the separation and transportation of photogenerated carriers. As a result, the photocatalytic hydrogen evolution rate achieves 129.75 μmol·h -1 (with 50 mg of photocatalysts) on the optimized CoO/h-TiO 2 heterostructures. This work provides a new design idea for the preparation of excellent TiO 2 -based photocatalysts.

Defective ZnIn 2 S 4 nanosheets/mesoporous black TiO 2 heterojunction hollow spheres (H-ZIS/b-TiO 2 ) are prepared through hydrothermal and surface low-temperature hydrogenation strategies, which show broad-spectrum response and excellent charge separation efficiency. This H-ZIS/b-TiO 2 flower-like heterojunction hollow spheres with a narrow band gap of ∼1.88 eV expand the light response to visible light and show excellent photocatalytic hydrogen evolution rate (278 μmol h -1 50 mg -1 ) under visible-light irradiation, which is 1.5 times as high as that of ZnIn 2 S 4 /black TiO 2 heterojunction hollow spheres (ZIS/b-TiO 2 ) (181 μmol h -1 50 mg -1 ). The excellent photocatalytic performance is due to the formation of O, S dual vacancies in b-TiO 2 and H-ZIS providing more active sites for photocatalytic reaction and improving the charge separation efficiency, heterojunctions promoting transport of photogenerated carriers, and the hollow structure increasing light utilization by reflecting light. The novel heterojunction hollow sphere with high performance has broad application prospects in the field of energy.

Metal-free heterogeneous catalysts are receiving more and more attention for wastewater remediation by activating peroxymonosulfate (PMS) due to their environmental benign. However, carbon-based materials as the most typical metal-free heterogeneous always suffer from poor durability. Inspired by the fact that a conjugated system may facilitate the electron transfer during PMS activation, we innovatively select polyaniline (PANI) as a new PMS activator and investigate its catalytic performance in detail. It is found that PANI can display better catalytic performance than traditional metal-based catalysts and popular N-doped carbocatalysts in methyl orange (MO) degradation. More importantly, PANI is not only universal for various pollutants degradation but also maintains its catalytic performance in repeated degradation experiments. The stable N sites in the conjugated chains and the oxidation-resistance benzene rings as the building units are considered to be responsible for such an excellent durability. In addition, the influences of some routine factors and actual water backgrounds are comprehensively checked and analyzed. The quenching experiments and electron paramagnetic resonance confirm that MO degradation is achieved through both radical and nonradical pathways, where SO 4 •- and 1 O 2 are primary reactive species. The reaction mechanism is also proposed with the assistance of X-ray photoelectron spectroscopy.