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CeO 2 nanoparticles are successfully loaded on carbonate doped Bi 2 O 2 CO 3 (CBOC) nanosheets by a facile hydrothermal and low-temperature calcination method. CeO 2 /CBOC heterojunction shows significantly enhanced photocatalytic activity, when 35 mg of CeO 2 /CBOC photocatalyst is added to tetracycline (TC) solution (20 mg/L, 100 mL), about 79.5% TC is degraded within 90 min under visible light irradiation, which is much higher than that of original CeO 2 and CBOC. According to photoelectrochemical characterization and active radical capture experiments, the Z-scheme electron transfer mechanism is the reason for the significant enhancement of photocatalytic activity. Besides, the XPS results indicate that Ce4+/Ce3+ redox pairs are formed at the contact interface between CeO 2 and CBOC, which is conducive to the transfer of photoexcited electrons and production of superoxide radicals. Additionally, the photocatalytic mechanism and possible degradation pathway of TC is proposed through free radical trapping experiments and liquid chromatography-mass (LC-MS) analysis. This study will accumulate experience for the combination of CeO 2 and bismuth-based nanomaterials, and provide a feasible way to design wide band-gap bismuth-based photocatalysts, thereby achieving efficient visible light degradation of environmental pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A flower-like CdS/K 2 Ta 2 O 6 S-scheme heterojunction was prepared. • The S-scheme charge transfer mechanism between CdS and K 2 Ta 2 O 6 was revealed. • Excellent ability for photocatalytic H 2 O 2 production from water and air. • The route and mechanism of the photocatalytic H 2 O 2 production were proposed. The hydrogen peroxide (H 2 O 2) production using solar energy is of great significance in chemical industry and environmental remediation. However, this technique requires that photocatalysts have efficient charge separation and migration efficiency. Herein, we designed a flower-like CdS/K 2 Ta 2 O 6 (CdS/KTO) S-scheme heterojunction with promoted charge separation and migration by a facile two-step hydrothermal strategy. The CdS/KTO photocatalyst exhibited an outstanding performance with a H 2 O 2 production rate of 160.89 μmol g−1 h−1 without using any sacrificial agents and adding additional O 2. The combination of the in situ irradiated X-ray photoemission spectroscopy (XPS), electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations revealed that the formation of an S-scheme heterojunction between CdS and KTO could greatly promote the separation of photogenerated electron-hole pairs toward efficient H 2 O 2 production. This work provides insights for the charge transfer mechanism of S-scheme heterojunction and an innovative stratagem for green, energy-saving and sustainable H 2 O 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Co LDH/C, O co-doped g-C 3 N 4 2D/2D heterojunction has been first fabricated. • The modification of 2-methylimidazole enhanced photoconversion efficiency. • 2D/2D heterojunction exhibits excellent molecular oxygen activation. • The formed charge carrier transfer pathway promotes photoelectron transfer. • 2D/2D heterojunction possesses weakened surface charge carrier recombination. Molecular oxygen is a green and low-cost oxidant, which can be activated to produce reactive oxygen species by solar-light-driven photocatalysis. Here, Ni-Co LDH infused C, O co-doped g-C 3 N 4 two-dimensional (2D) ultrathin nanosheet was prepared by a simple thermal polymerization coupling hydrothermal method. The molecular oxygen activation was estimated by the quantitative determination of •O 2 − and 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. 2D/2D heterojunction exhibits impressive photocatalytic performance. The arrestive activation efficiency is derived from the regulated energy band position, the broadened solar light absorption range, and the enhanced photoexcited electron transfer. Benefitting from these merits, the surface charge transfer efficiency of 2D/2D heterojunction is promoted to 51.3% from 14.3% (g-C 3 N 4). The surface recombination rate constant is reduced to 0.0011 s−1 from 0.0042 s−1 (g-C 3 N 4). The feasible photocatalytic mechanism for molecular oxygen activation is expounded based on experimental analysis. [ABSTRACT FROM AUTHOR]

• FeOOH QDs/CQDs/g-C 3 N 4 0D/2D heterojunction has been first prepared. • 0D/2D heterojunction can realize H 2 O 2 generation and in-situ decomposition. • The composite has excellent charge carrier transfer and separation efficiency. • The introduction of CQDs can improve the photoconversion efficiency. • The generated Fe2+ in FeOOH QDs can promote H 2 O 2 in-situ decomposition. Hydrogen peroxide (H 2 O 2) was generally considered as an ideal energy carrier and environment-friendly oxidant to process environmental modification. Here, FeOOH QDs and CQDs was interspersed on g-C 3 N 4 ultrathin nanosheet to promote H 2 O 2 generation and in-situ decomposition. FeOOH QDs/CQDs/g-C 3 N 4 composite (FCCN) exhibited excellent photoactivity for degrading oxytetracycline (OTC) under visible light illumination. The accelerated photoactivity is ascribed to the following merits: 1) the exciton dissociation interface and carrier transfer channel are fabricated to facilitate photoexcited electron transfer; 2) the photoexcited electron can be rapidly utilized by molecular oxygen to generate H 2 O 2 , resulting in facilitated molecular oxygen activation; 3) Fe3+ in FeOOH QDs is reduced to Fe2+ by photoexcited electron, and then reacts with generated H 2 O 2 to produce OH, thereby promoting photodegradation efficiency. The H 2 O 2 generation yield of FCCN-2 composite was 224.24 µmol h−1 g−1, which was higher than that of pure g-C 3 N 4. 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and O 2 − quantitative determination displayed outstanding molecular oxygen activation capacity of hybrid composite. Moreover, 0D/2D heterojunction photocatalyst displayed weakened charge carrier recombination efficiency (0.0015 s−1) and expedited surface carrier transfer efficiency (41.01%) compared to g-C 3 N 4 and CQDs/g-C 3 N 4 photocatalyst. Finally, the photodegradation mechanism were rationally evaluated based on the experiment results. [ABSTRACT FROM AUTHOR]

• The 2D/2D Bi 2 MoO 6 /Ti 3 C 2 MXene interfacial Schottky heterojunction was first prepared. • 2D/2D Schottky heterojunction accelerated charge carrier separation and transfer. • The formed built-in electric field facilitated hot electron to inject into active sites. • 2D/2D Schottky heterojunction showed superior molecular oxygen activation. • This study paved the new way to realize high molecular oxygen activation efficiency. Visible-light-driven molecular oxygen activation (MOA) is deemed as the potential route to enhance oxidation capacity of molecular oxygen, while activation efficiency is significantly impeded thanks to the deficient charge carrier separation and transfer. In this work, an atomic scale 2D/2D Schottky heterojunction is prepared using titanium carbide as 2D platform for in situ growth of 2D ultrathin bismuth molybdate nanosheet through anaerobically hydrothermal conditions. This 2D/2D Schottky heterojunction displays high performance for MOA, which is 5.56-fold higher than pristine one. The excellent activation efficiency is originated from ultrahigh charge carrier transfer channel, in which the surface charge transfer efficiency is enhanced (30.73 % vs 18.45 %) and the surface recombination constant is decreased (0.0019 s−1 vs 0.0031 s−1) compared to pristine one. The mechanism of photocatalytic MOA is unearthed based on experiment results and various characterizations. This study shows the great potential of atomic scale 2D/2D Schottky heterojunction in photocatalytic MOA. [ABSTRACT FROM AUTHOR]