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Inducing amorphous components into Al2O3 leads to elongation of the Al–O bond and the formation of oxygen vacancies, which makes Al2O3 an independent photocatalyst for CO2 adsorption and reduction.

α-Bi2O3/Bi5NO3O7 heterojunctions are constructed, and show higher separation efficiency but lower photocatalytic activity. The reasons are related to the shift of energy band positions.

A well-designed photocatalyst with excellent activity and selectivity is crucial for photocatalytic CO2 conversion and utilization. TiO2 is one of the most promising photocatalysts. However, its excessive surface oxidation potential and insufficient surface active sites inhibit its activity and photocatalytic CO2 reduction selectivity. In this work, highly dispersed Bi2Ti2O7 was introduced into defective TiO2 to adjust its oxidation potential and the generation of radicals, further inhibiting reverse reactions during the photocatalytic conversion of CO2. Moreover, an in situ topochemical reaction etching route was designed, which achieved defective surfaces, a contacted heterophase interface, and an efficient electron transfer path. The optimized heterophase photocatalyst exhibited 93.9% CH4 selectivity at a photocatalytic rate of 6.8 μmol·g−1·h−1, which was 7.9 times higher than that of P25. This work proposes a feasible approach to fabricating photocatalysts with well-designed band structures, highly dispersed heterophase interfaces, and sufficient surface active sites to effectively modulate the selectivity and activity of CO2 photoreduction by manipulating the reaction pathways.

Efficient separation of electrons and holes in photocatalysis plays a key role in achieving high efficiencies of CO2 reduction. The available built-in electric field could separate the photogenerated charges and...

The development of metal sulfide catalysts with remarkable activity toward efficient overall photocatalytic water splitting remains challenging owing to the dominant charge recombination and deficient catalytic active sites. Moreover, in the process of water oxidation catalysis, the inhibition of severe photocorrosion is an immense task, requiring effective photogenic hole-transfer kinetics. Herein, stratified Co-MnO2@CdS/CoS hollow cubes with spatially separated catalytic sites were rationally designed and fabricated as highly efficient controllable catalysts for photocatalytic overall water splitting. The unique self-templated method, including a continuous anion/cation-exchange reaction, integrates a Co-doped oxidation co-catalyst (Co-MnO2) and a reduction co-catalyst (CoS) on the nanocubes with uniform interface contact and ultrathin two-dimensional (2D) nanometer sheets. We demonstrate that the stratified Co-MnO2@CdS/CoS hollow cubes can provide an abundance of active sites for surface redox reactions and contribute to the separation and migration of the photoionization charge carriers. In particular, CoS nanoparticles dispersed on the walls of CdS hollow cubes were identified as reduction co-catalysts accelerating hydrogen generation, while Co-MnO2 nanosheets attached to the inner walls of the CdS hollow cube were oxidation co-catalysts, promoting oxygen evolution dynamics. Benefiting from the desirable structural and compositional advantages, optimized stratification of Co-MnO2@CdS/CoS nanocubes provided a catalytic system devoid of precious metals, which exhibited a remarkable overall photocatalytic water-splitting rate (735.4 (H2) and 361.1 (O2) μmol h−1 g−1), being among the highest values reported thus far for CdS-based catalysts. Moreover, an apparent quantum efficiency (AQE) of 1.32% was achieved for hydrogen evolution at 420 nm. This study emphasizes the importance of rational design on the structure and composition of photocatalysts for overall water splitting.

In previous studies, it has been shown that phosphorus and phosphate can improve the conductivity, change the electronic structure, and accept electrons from catalysts. In this study, we obtained phosphorylated NiAl-layered double hydroxide (P-LDH) nanosheets and used them as a novel cocatalyst in photocatalytic hydrogen evolution. After assembly with g-C3N4 via an in situ process, these noble-metal-free composite photocatalysts showed superior photocatalytic hydrogen evolution activity. It was also found that the efficiency of H2 production on the optimal composite was 1.5 times that of Pt-modified g-C3N4. Characterization of the photocatalysts revealed that the effects of P-LDH were different from those of other bimetallic LDHs, showing a lower overpotential and faster reaction kinetics of H2 evolution. Moreover, it was found that P-LDH has a higher surface work function than that of g-C3N4, leading to the formation of an interfacial electric field from CN toward P-LDH. Therefore, modifying P-LDH can efficiently improve the interfacial charge transfer rate, suppress photogenerated charge recombination, and lower the surface overpotential of g-C3N4. This study serves as guidance on the design of more effective cocatalysts for photocatalytic hydrogen evolution reactions.

In this paper, it is found that the preferential growth of secondary {117} facets of Bi24O31Br10 into dominant facets would lead to higher photocatalytic activity, although the original main {213} facet has a stronger molecular oxygen adsorption ability, which illustrates that the charge separation efficiency induced by dominant/secondary facet control plays a more important role than that of O2 adsorptive performance in improving activity.

Hierarchical porous CoFe-LDHs composed of ultrathin nanosheets were successfully prepared by a simple one-step precipitation process of Co2+ and Fe3+ ions, avoiding multiple tedious steps. The optimized composition and the hierarchical porous structure design of the CoFe-LDHs endow them with high activity for OER in alkaline media (1 M KOH). Benefiting from the synergistic catalytic effects of the controllable composition and the structural features of CoFe-LDHs, the superior OER performance of hierarchical porous Co8Fe1-LDH nanosheets with optimal composition is achieved with the smallest overpotential (262 mV at 10 mA cm−2), lowest Tafel slope (42 mV per decade), and excellent long-term stability, which is superior to previously reported LDH-derived and commercial iridium dioxide (IrO2) electrocatalysts, suggesting its promising application as an efficient electrode for OER.

In this paper, a novel ionic liquid-assisted solvothermal method to prepare Cl-doped bismuth oxycarbonate (Bi2O2CO3) is presented. The ionic liquid of [Hnmp]Cl not only enhances the solvothermal process to help the formation of Bi2O2CO3, but also provides chloride element as a dopant. XRD and XPS show that all three samples are Bi2O2CO3 with high purity. XPS, solid EPR, and TEM results prove that Cl is doped into the Bi2O2CO3 lattice and oxygen vacancies are generated. DRS results show that after Cl doping, the absorption of visible light by Bi2O2CO3 is enhanced. Surface photovoltage (SPV) and transient photocurrent tests show that as the doping amount of Cl increases, the separation efficiency of photogenerated electron–hole pairs over Bi2O2CO3 improves. The photocatalytic activity of Bi2O2CO3 is evaluated by the degradation of rhodamine B, which is increased after Cl doping. This work would broaden the application of ionic liquids in the solvothermal process and deepen the understanding of anionic ion doping in Bi2O2CO3.

In this paper, it is found that the preferential growth of secondary {117} facets of Bi

A well-designed photocatalyst with excellent activity and selectivity is crucial for photocatalytic CO

Piezocatalysis, converting mechanical vibration into chemical energy, has emerged as a promising candidate for water-splitting technology. However, the efficiency of the hydrogen production is quite limited. We herein report well-defined 10 nm BaTiO3 nanoparticles (NPs) characterized by a large electro-mechanical coefficient which induces a high piezoelectric effect. Atomic-resolution high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning probe microscopy (SPM) suggests that piezoelectric BaTiO3 NPs display a coexistence of multiple phases with low energy barriers and polarization anisotropy which results in a high electro-mechanical coefficient. Landau free energy modeling also confirms that the greatly reduced polarization anisotropy facilitates polarization rotation. Employing the high piezoelectric properties of BaTiO3 NPs, we demonstrate an overall water-splitting process with the highest hydrogen production efficiency hitherto reported, with a H2 production rate of 655 μmol g-1 h-1 , which could rival excellent photocatalysis system. This study highlights the potential of piezoelectric catalysis for overall water splitting.

Promoting photogenerated carriers separation and adjusting the activation path of the CO2 molecule are two effective solutions for improving the activity and selectivity of photocatalytic CO2 reduc...

Ferroelectric ceramics possess great application potential in optoelectronic and solar energy devices. However, ferroelectric ceramics normally have large band gaps, strongly inhibiting their photovoltaic performances. In this work, we use a strategy to enhance the visible light absorption of ferroelectric ceramics by incorporating Au nanoparticles into the ferroelectric BaTiO3(BT) matrix. The BT-Au nanohybrids are preliminarily synthesized as the “building blocks”, which are assembled and then sintered as the 0–3 type composite ceramic. We find that the UV–vis absorption of composite ceramic is improved by localized surface plasmon resonances (LSPRs). While the ferroelectric property of the 0–3 type BT-Au ceramic remains robust. As a result, the composite ceramics show excellent ferroelectric photovoltaic effect with a photocurrent being approximately seven times as that in pure BT ceramics and an open-circuit voltage of 6 V. These findings suggest that interfacial control of ceramic composites may act an effective approach to optimize the photovoltaic responses in ferroelectric ceramics.

In this work, N-methyl-2-pyrrolidonium (NMP) was acidized using hydrochloric acid to obtain [Hnmp]Cl first, which was then reacted with FeCl3 to prepare a series of inexpensive tunable [Hnmp]Cl·xFeCl3 (x = 0.2–2.0) ionic liquids (ILs) for the extractive and oxidative desulfurization of model oils. The Lewis acidities of these ILs were tested by the Fourier transform infrared (FT-IR) method, which indicated that when the x value of [Hnmp]Cl·xFeCl3 was above 1.0, the ILs exhibited Lewis acidity. The extraction results showed that the acidification of NMP reduced its dissolubility ability toward dibenzothiophene (DBT) and its Lewis acidity played a determining role in extractive desulfurization. In the catalytic oxidation removal process of the DBT model oil in the presence of H2O2, electron paramagnetic resonance (EPR) and scavenger experiments showed that the hydroxyl radical (˙OH) plays a key role and the superoxide anion radical (O2˙−) has a minor function. [Hnmp]Cl·1.5FeCl3 IL showed excellent recycling performance, which was due to its high dissolving capacity (23 700 ppm) for dibenzothiophene-sulfone (DBTO2).

Improving charge separation efficiency and accelerating surface reaction kinetics are two challenging issues for the graphitic carbon nitride (g-C3N4) photocatalyst. Surface atom decoration is a facile and efficacious strategy to modulate the electronic structure and then affect the local spatial charge separation of the photocatalyst. Here, we first reported a surface P atom grafting strategy for g-C3N4via P–N bond formation to effectively promote the local spatial charge separation and ample reactive sites. The post-calcination process allowed controllable grafting of P–OH at the corner-nitrogen sites in tri-s-triazine of g-C3N4, which resulted in an impurity state, and it acted as an electron capture center for local spatial charge separation and reactive sites. Thus, the surface N–P–OH bond modulation of g-C3N4 rendered nearly four-fold enhancement in the hydrogen evolution rate. The ability to build pure surface P–N motif modulation presents a promising strategy to realize the precise band engineering of modulated g-C3N4. These findings would deepen the understanding of the nonmetal atom decoration-related issues of g-C3N4-based materials.

Promoting electron-hole separation and migration and lowering the overpotential of hydrogen evolution reactions are two effective solutions for improving photocatalytic hydrogen performance. Suitable co-catalyst and appropriate interfacial contacts can effectively lower overpotential and can also construct an electric field at the interface to increase the separation efficiency of the carriers. In this work, we design and fabricate a 2D-2D type of Ni2P co-catalyst modified with ZnIn2S4 for boosting the performance of photocatalytic hydrogen evolution. As a co-catalyst, the 2D Ni2P nanosheets exhibit a lower overpotential and smaller charge transfer resistance in hydrogen evolution reactions, and is much improved in both respects compared to Ni2P nanoparticles. Based on this, 2D/2D Ni2P/ZnIn2S4 nanohybrids with large contact regions and shorter transmission distances of the charges were fabricated, which effectively improve the separation of photo induced carriers and the interfacial charge transfer. By taking advantage of the above features, the fabricated 2D-2D Ni2P/ZnIn2S4hybrid exhibits a superior hydrogen evolution rate of 2066 μmol·h−1·g−1 under visible light irradiation, and the apparent quantum yield was 7.7% at 420 ± 20 nm. This activity far exceeds performance of the 0D/2D Ni2P/ZnIn2S4 hybrid, and is ascribed to better charge separation and accelerated surface reactions of the Ni2P nanosheets.

Developing nano-ferroelectric materials with excellent piezoelectric performance for piezo-catalysts used in water splitting is highly desired but also challenging, especially with respect to reaching large piezo-potentials that fully align with required redox levels. Herein, hetero-epitaxial strain in BaTiO 3 nanoparticles with a designed porous structure is successfully induced by engineering their surface reconstruction to dramatically enhance their piezoelectricity. The strain coherence can be maintained throughout the nanoparticle bulk, resulting in a significant increase of the BaTiO 3 tetragonality and thus its piezoelectricity. Benefiting from high piezoelectricity, the as-synthesized blue colored BaTiO 3 nanoparticles possess a superb overall water-splitting activity, with H 2 production rates of 159 μmolg -1 h -1 , which is almost 130 times higher than that of the pristine BaTiO 3 nanoparticles. This work thus provides a generic approach for designing highly efficient piezoelectric nano-materials by strain engineering that can be further extended to various other perovskite oxides, including SrTiO 3 , enhancing their potential for piezoelectric catalysis.

The main process of carbon dioxide (CO2) photoreduction is that excited electrons are transported to surface active sites to reduce adsorbed CO2 molecules. Obviously, electron transfer to the active site is one of the key steps in this process. However, current catalysts for CO2 adsorption, activation, and electron reduction occur in different locations, which greatly reduce the efficiency of photocatalysis. Herein, through a spontaneous chemical redox approach, the plasmonic photocatalysts of Au-BiOCl-OV with enhanced interfacial interaction were fabricated for visible light CO2 reduction through the simultaneous adsorption, activation and in situ reduction of CO2 without a sacrificial agent. By loading gold (Au) on the oxygen vacancy (OV), Au and BiOCl-OV formed a direct and tight interface contact, whose fine structure was confirmed by SEM, TEM, EPR and XPS, which not only effectively boosts the light utilization efficiency and the light carrier separation ability, but also can simultaneously adsorb, activate and in situ reduce carbon dioxide for highly efficient visible light photocatalysis. Thanks to the synergistic influence of Au and OV, Au-BiOCl-OV exhibits excellent photocatalytic performance without sacrificial agent and outstanding stability with a high CO and CH4 production yield, reaching 4.85 μmol g-1 h-1, which were 2.8 times higher than C-Au-BiOCl-OV (obtained by traditional NaBH4 reduction). This study proposes a new strategy for the production of high-performance collaborative catalysis in photocatalytic CO2 reduction.

Photocatalysis has attracted wide attention in eliminating volatile organic compounds (VOCs). This paper pays attention to the relationship between structure and performance of photocatalysts based on the fact that catalytic reactions arise on the surface of catalysts and the interface structure of photocatalysts plays key role in transfer efficiency of charges carriers. This review summarizes various surface/interface designs including unsaturated coordination such as oxygen vacancies, surface halogenations, and heterojunctions, homojunctions, facets, etc., as well as the application in photocatalytic degradation of VOCs. This paper reviews the influence of surface and interface properties of materials on VOCs molecules, effective strategies to promote the decomposition of VOCs from the perspectives of VOCs activation, reaction barrier etc., and presents various methods of photocatalyst design appropriately. The degradation path of highly toxic benzene VOCs are also summarized. In addition, the possible problems and suggestions for photocatalytic degradation of VOCs are proposed.

Constructing heterojunctions would result in the change of valence band position, which is an important factor determining the oxidative ability of photo-induced holes, has received scant attention. In this paper, β-Bi

Methane is a greenhouse gas that contributes to global warming. Hence, effectively removing the low concentration (1000 ppm) of methane in the environment is an issue that deserves research in the field of catalysis. In this study, oxygen-magnesium bivacancies are simultaneously imbedded into MgO by designing an in situ reduction combustion atmosphere for oxygen release and substituting magnesium with carbon to induce the formation of magnesium vacancies. The DFT calculations reveal that the surface electron density of MgO is improved by the oxygen vacancy structure and the substitution of Mg by C in bulk; this accelerates migration of the charge from the material surface to the adsorbed oxygen species, which leads to abundant surface peroxide species that enable activation and oxidation of methane at a low temperature (below 200 °C). This work could provide a concept for developing non-noble or transition metal oxides for low-temperature activation and conversion of alkanes in the thermocatalytic field through reactive oxygen species.

Correction for ‘Insight into the relationship between redox ability and separation efficiency via the case of α-Bi2O3/Bi5NO3O7’ by Jie-hao Li et al., Inorg. Chem. Front., 2022, 9, 3578–3589, https://doi.org/10.1039/D2QI00731B.

Photocatalysis has been facing challenging problems especially the inefficient photocarriers transfer at the interfaces. Here, based on Ksp difference, we prepare the sequential heterojunction of CoS/CdS/CuS via sequential cation exchange strategy, and propose the concept of "electron-welcome zone", where the point-to-point contact can be formed at the interface, thus providing continuous electron transport channels. HAADF-STEM EDS line test indicates the formation of designed structures, and the p/n junction is confirmed by band structure and Mott-Schottky analysis. Theoretical calculation indicates that CoS reduces the Gibbs free energy of the reaction. TRPL spectra show that the existence of "electron welcome zone" greatly improves the lifetime of electrons. This sequential structure enable the optimal H2 production rate to reach 123.2 mmol g−1 h−1 with AQE of 45.6%, which is among the highest values of CdS-based photocatalysts. This work opens new way to efficient photogenerated carrier transfer channel for solar-energy conversion.

Heterostructured Bi3O4Br/α-Bi2O3 nanocomposites are prepared via in situ one-step self-combustion of ionic liquids. Tetrabutylammonium bromide (TBAB) is employed to be fuel, complexing agent for ionic liquids, as well as the reactant supplying Br for the objective material. The ratio of Bi3O4Br/α-Bi2O3 can be easily adjusted by controlling the amount of TBAB. The heterojunctions show higher photocatalytic ability towards both azo dye methyl orange (MO) and colorless pollutant phenol. The electron spin resonance (ESR) test and p-nitro blue tetrazolium chloride (NBT) degradation result indicate that generation amounts of superoxide anion radicals ( O2−) over heterojunctions are less than that over pure Bi3O4Br. Photoelectrochemical measurements show that separation efficiencies of photo-generated electrons and holes are decreased after the combination of Bi3O4Br and α-Bi2O3. Work function test and scavenger experiments display that holes play key role for pollutant degradation and the position of holes on α-Bi2O3 is lowered via hybridization. Thus, the enhanced photocatalytic activity over composites can be attributed to the position decline of α-Bi2O3 valence band, thus improving the reactivity of holes in direct oxidation of pollutants. In this case, valence band position is confirmed to be more important than separation efficiency of charge carriers in affecting photocatalytic performance.

As emerging noble metal-free co-catalysts, transition metal phosphides have been employed to improve photocatalytic H2 production activity. Herein, the metallicity of CoP, as a representative phosphide, and the Schottky effect between CoP and g-C3N4 are confirmed via theoretical calculations. Then, a 2D/2D structure is designed to enlarge the Schottky effect between the interfaces, for which the apparent quantum efficiency of the photocatalytic H2 evolution is 2.1 times that of corresponding 0D/2D heterojunctions. The morphology, microstructure, chemical composition, and physical nature of pristine CoP, g-C3N4, and the composites are characterized in order to investigate the dynamic behavior of photo-induced charge carriers between CoP and g-C3N4. Based on the measurements, it is proposed that the efficient electron collecting effect of CoP can be attributed to the superior interfacial contact and Schottky junction between the CoP and g-C3N4 interfaces. Furthermore, the excellent electrical conductivity and low overpotential of CoP make water reduction easier. This work demonstrates that the construction of a 2D/2D structure based on a suitable Fermi level is crucial for enhancing the Schottky effect of transition metal phosphides.

Hollow cobalt nickel oxide microspheres assembled by ultrathin porous nanosheets with tunable Co/Ni molar ratios have been successfully synthesized via a facile “self-template” method, taking solid bimetallic alkoxide microspheres as a precursor. The compositions and the sizes of the hollow cavities of cobalt nickel oxides can be easily controlled by the Co/Ni molar ratios and the size of bimetallic alkoxide microspheres, respectively. The electrochemical measurements indicate that the cobalt nickel oxide catalysts exhibit greatly enhanced oxygen evolution reaction (OER) activity in alkaline media, and Co2–Ni1–O microspheres with the optimal composition show the lowest overpotential (∼310 mV for 10 mA cm−2) and the smallest Tafel slope (57 mV per decade). This is attributed to the large electrochemically reactive surface and good charge conduction offered by the synergetic effects between their unique structural features and tunable compositions. The hollow cobalt nickel oxide microspheres may serve as promising noble-metal-free OER electrocatalysts to replace IrOx material, and the synthetic strategy that directs structural design can be applied to prepare other multifunctional materials.

The development of high-efficiency and low-cost photocatalysts in photocatalytic H 2 evolution systems from water remains challenging. The substitution of a noble metal as the co-catalyst is still one of the important and meaningful issues in this field. Herein, we report a series of CaIn 2 S 4 catalysts combined with Ni 2 P, which acts as the co-catalyst, for boosting photocatalytic hydrogen evolution under visible light. The integrated system of the Ni 2 P/CaIn 2 S 4 composite exhibited high efficiency and durability, which were even higher than those of Pt decorated catalysts. The promoting effect of Ni 2 P can be ascribed to its excellent reductive ability and analogous metallic character, which can accelerate the transfer and consumption of the photo-generated electrons. Moreover, based on the surface photo-voltage technique and electrochemical tests, the unique mechanism of Ni 2 P for the movement of photo-generated charges during the photocatalysis process is proposed for the first time.

Nano-ZnFe2O4 photocatalysts are one-step synthesized via solution combustion route, which are characterized by XRD, TEM, and UV-vis DRS. The photocatalytic activity of these samples are evaluated by the removal of thiophene in model oil under visible light irradiation. The influences of fuel amount on the particle size and photocatalytic performance of the as-synthesized catalysts are investigated. The results show that the ZnFe2O4 with the particle size of 21.9 nm exhibits the highest photocatalytic ability, which is acquired using triethylamine hydrochloride as fuel in the fuel-rich combustion condition. The desulfurization yield of model oil can reach 92.5% in 5 h photo-irradiation and the sulfur content can be decreased from 200 ppm to 15 ppm.

Molecular oxygen is the greenest potential oxidant, but its spin-forbidden nature limits its activation and application. The use of photocatalysis technology to activate molecular oxygen into reactive oxygen species (ROS) is a feasible strategy for initiating molecular oxygen activation performance from the activation methods of energy transfer process and charge transfer process, such as improving the efficiency of inter-system crossing, reducing non-radiative decay, and enhancing molecular oxygen adsorption and charge separation efficiency. New perspectives on the analysis of molecular oxygen activation pathways and the detection methods of ROS are introduced. In addition, the application of activated molecular oxygen in some oxidative reactions including degradation of organic pollutants, organic synthesis and photodynamic therapy of tumors are summarized. Finally, conclusions and challenges are briefly presented.

Polymeric carbon nitride is a promising candidate for photocatalytic hydrogen evolution but mostly just shows moderate activity because of its inefficient charge separation and sluggish surface reaction kinetics. Phase-based heterostructures, especially crystal-phase heterostructures that are composed of identical compositions with different crystal phases, can endow nanomaterials with promising properties and efficient photocatalysis applications. In this study, a novel crystalline hexagonal-C3N4/g-C3N4 hetero-phase junction was synthesized using a direct in situ alkali salt template coupled with organic solvents strategy. High hydrophilicity was obtained because of the synergistic effect between alkali salt and organic solvents in the polycondensation process. The greatly increased separation and transfer efficiency of charge carriers and the improved proton absorption in the surface reaction of the photocatalyst were achieved by the constructed phase junctions between the crystalline hexagonal-C3N4 and amorphous g-C3N4 decorated with numerous hydrophilic groups. Thus, the carbon nitride hetero-phase junction exhibited dramatically enhanced photocatalytic performance in hydrogen evolution and excellent cycling stability under visible light irradiation. This work presents a novel insight into phase engineering based on carbon nitride materials with surface functional modification for an efficient photocatalytic activity.

In layered Bi-O-X materials, {001} and {110} facets are regarded to be highly active. However, dominant facets in bismuth-rich materials are rarely studied so far. In this paper, the role of main {314} facet of Bi5O7I is investigated for the first time. Bi5O7I samples with adjustable {314} and {008} facet ratios are synthesized using ionic liquid self-combustion method. The inducing growth role of tetramethylammonium iodide for {314} main facet is revealed. Photocatalytic experiments indicate that the activity of Bi5O7I material with {314}/{008} facet ratio of 4.32 are lower than those of Bi5O7I with facet ratio of 5.23 and 4.56, implying the increase of {008} facet proportion could not effectively improve the redox performance. Meanwhile, the controllable oxygen vacancy concentration can be realized by constructing reduction atmosphere. Photoelectrochemical test results show that the synergistic effect of facet ratio and the oxygen vacancies lead to the improvement of charge carriers.

The mismatches of lattices and energy bands in heterojunction are the dominant factors restricting the generation efficiency of reactive oxygen species (ROS) that are powerful tools for water purification and anti-bacteria. In this paper, the mediated lattice matching role of amorphous Al 2 O 3 is presented for constructing the ternary g-C 3 N 4 /Al 2 O 3 /ZnO heterojunctions, which exhibit higher molecular oxygen activation performance than binary g-C 3 N 4 /ZnO and g-C 3 N 4 /Al 2 O 3 heterojunctions. The oxygen activation ability and the ROS generation were testified by the electron paramagnetic resonance (EPR) measurement, transformation of nitroblue tetrazolium (NBT) and degradation of methylene blue (MB). The ROS include superoxide anion radical ( O 2 − ) and consequent product of hydroxyl radical ( OH). The superior oxygen activation performance of the ternary heterojunctions can be attributed to the lattices matching of the mediated amorphous Al 2 O 3 and the resultant efficient cascade electron transfer.

Homogeneous ultrathin g-C3N4 nanosheets/Al2O3 heterojunctions are synthesized using melamine and Al(NO3)3 via in-situ reaction and the following thermal polymerization approach. The in-situ reaction between melamine and Al(NO3)3 results in the existence of HNO3-acidified melamine and Al(OH)3 aggregates via the hydrolysis of Al(NO3)3. After thermal polymerization, the aggregates are converted to g-C3N4/Al2O3 composites. The thermal polymerization of acidified melamine and the support effect of aluminum hydroxide for g-C3N4 during the calcination process lead to highly dispersed amrophous Al2O3 on ultrathin g-C3N4 nanosheets, which is beneficial for the separation of photogenerated electron-hole pairs in the heterojunction. The degradation rate for Rhodamine B (RhB) over the most activie sample is 16.6 times than that of pristine g-C3N4 under visible light irradiation, which can be attributed to the high specific surface area, highly dispersion of amorphous Al2O3 on ultrathin g-C3N4 nanosheet, and the effective electrons transfer from g-C3N4 to the amorphous Al2O3.

Developing inexpensive photocatalysts is of great value for industrial applications. In the work, magnesia–alumina spinel (MgAl2O4) made from earth-abundant elements is synthesized via a simple hydrothermal route and subsequent calcination. Theoretical calculation indicates that pure MgAl2O4 crystal has an energy band gap of 7.505 eV, and that the top of the valence band is mainly formed by hybridization between Mg-p and O-p states, while the bottom of the conduction band mainly originates from the Mg-s/p and O-s/p states. The UV-vis DRS results show that MgAl2O4 containing amorphous matter absorbs ultraviolet light with a band gap of 3.90 eV, which arises from the longer Mg–O bond length and presence of defects. This research also confirms that the visible-light photocatalytic activity reported in a previous paper is derived from the nitrogen element doping. The photocatalytic activity of MgAl2O4 is evaluated via the decomposition of methylene blue (MB) under UV-vis light illumination. The electron transfer route and the photocatalytic mechanism of MgAl2O4 for degrading MB are proposed. For the first time, the potentials of the energy bands of MgAl2O4 are obtained using Mott-Schottky electrochemical measurement.