Photocatalytic H2 Production Rate Research Articles

Selenium doping to improve internal electric field for excellent photocatalytic efficiency of g-C3N4 nanosheets

Graphitic carbon nitride is a promising photocatalyst to address environmental issues and energy applications. Herein, we develop an efficient defect-containing functionalized system of 2D selenium doped g-C3N4 porous nanosheets via one pot with two-step temperature for the first time. During heat treatment, Se-infused g-C3N4 nanosheets loosen stacking and form thinner nanosheets, which could effectively shorten the electronic path of charge migration. The introduction of nitrogen vacancies creates a midgap energy state below the CB, which improves the light-harvesting efficiency. Moreover, the dual effect of N vacancy and Se doping provides a driving force for the dissociation of excitons and achieves an effective spatial charge separation. High specific surface area (104.1 m2/g), suitable bandgap (2.65 eV), and good photocurrent response (0.45 µA cm−2) help to enhance the photocatalytic efficiency of 1-SeCN remarkably. Henceforth, high photocatalytic H2 production rate of 5441 µmol g−1 h−1 and CO evolution rate of 31.5 µmol g−1 h−1 verifies the effective Se doping enhances the photocatalytic efficiency of g-C3N4. Furthermore, DFT calculations are consistent with experimental results and this facile engineering strategy provides a scalable way to develop a novel, efficient g-C3N4-based photocatalyst for H2 production and CO2 reduction.

The enhancement of photocatalytic hydrogen production over Ag2WO4 modified g-C3N4 with Pt as cocatalyst

ABSTRACT The construction of heterojunction photocatalyst is an effective mean to improve the photoexcited electron–hole pair separation. The Ag2WO4-doped graphitic carbon nitride (g-C3N4, C3N4 for short) composite photocatalysts were fabricated by a simple calcination and in-situ depositing strategy. The composites were characterized by different techniques. The effects of Ag2WO4 content, type of scavengers, pH value of reaction solution and dose of scavenger on photocatalytic hydrogen (H2) generation were studied. It was found that the Ag2WO4 micro-nano particles were highly dispersed on the C3N4 surface. After doping Ag2WO4, the light absorption range of Ag2WO4-C3N4 material was broadened effectively from 440 nm to 448 nm, and the BET surface area of C3N4 was increased from 35.63 to 40.73 cm2·g−1, indicating that Ag2WO4 loading could provide some new BET surface areas. The binding energy of all elements in Ag2WO4-4/C3N4 was clearly shifted due to the charge transfer from C3N4 to Ag2WO4, implying a strong interaction between C3N4 and Ag2WO4. The photocatalytic H2 production rate of the optimized Ag2WO4-4/C3N4 was 6047.4 μmol·g−1·h−1, which was 2.04 and 171.8 times that of C3N4 and Ag2WO4, respectively. While Ag2WO4-4/C3N4 exhibited a poor H2 production performance in the absence of Pt co-catalyst (309.3 μmol·g−1·h−1), indicating the formation of heterojunction among Ag2WO4, C3N4 and Pt.

Optimization of Schottky barrier height and LSPR effect by dual defect induced work function changes for efficient solar-driven hydrogen production

Photocatalytic water splitting for hydrogen evolution provides a desired approach for sustainable clean energy. However, increasing the effective electron density for proton reduction remains a huge challenge due to the fast charge recombination kinetic. Herein, we propose an efficient strategy, based on manipulating the Schottky barrier height (SBH) and localized surface plasmonic resonances (LSPR) effect of Co-MoO2-x via dual defect (Co doping and oxygen vacancies) induced work function change, to achieve higher electrons density in plasmonic CdS/Co-MoO2-x@C Schottky junction photocatalyst for the first time. Through varying the Co heteroatom doping and oxygen vacancies in our Co-MoO2-x@C cocatalyst, we show adjustable SBH at the interface and tunable photothermal effect in CdS/Co-MoO2-x@C, which leads to inhibited energetic electrons backflow in metallic Co-MoO2-x to improve the electron density. Moreover, optimized electronic structure gives rise to a zero-approaching Gibbs free energy for intermediate state, enabling CdS/Co-MoO2-x@C with promoted intrinsic H2 evolution kinetics.Furthermore, the extended light absorption and elevated reaction temperature stemming from strong LSPR effect of Co-MoO2-x contribute to the decrease of apparent activation energy from 13.824 to 6.579 kJ/mol for H2 evolution. To this end, CdS/Co-MoO2-x@C-7 photocatalyst yields a full-spectrum driven photocatalytic H2 production rate of 89.95 mmol g−1h−1, surpassing most reported CdS-based photocatalyst. This study opens a new avenue toward construction of efficient broad-spectrum active photocatalyst.

Modulating the Primary and Secondary Coordination Spheres of Single Ni(II) Sites in Metal-Organic Frameworks for Boosting Photocatalysis.

Though the coordination environment of single metal sites has been recognized to be of great importance in promoting catalysis, the influence of simultaneous precise modulation of primary and secondary coordination spheres on catalysis remains largely unknown. Herein, a series of single Ni(II) sites with altered primary and secondary coordination spheres have been installed onto metal-organic frameworks (MOFs) with UiO-67 skeleton, affording UiO-Ni-X-Y (X = S, O; Y = H, Cl, CF3) with X and Y on the primary and secondary coordination spheres, respectively. Upon deposition with CdS nanoparticles, the resulting composites present high photocatalytic H2 production rates, in which the optimized CdS/UiO-Ni-S-CF3 exhibits an excellent activity of 13.44 mmol g-1, ∼500 folds of the pristine catalyst (29.6 μmol g-1 for CdS/UiO), in 8 h, highlighting the key role of microenvironment modulation around Ni sites. Charge kinetic analysis and theoretical calculation results demonstrate that the charge transfer dynamics and reaction energy barrier are closely correlated with their coordination spheres. This work manifests the advantages of MOFs in the fabrication of structurally precise catalysts and the elucidation of particular influences of microenvironment modulation around single metal sites on the catalytic performance.

Visible light-induced H2 production and pollutant degradation by copper oxide nanosphere embedded zinc-cadmium-sulfide composite

AbstractGreen hydrogen production using solar water splitting and solving water pollution issues are intricately intertwined global goals which are hindered by the scarcity of highly active photocatalytic materials. Herein, we have presented a simple strategy to couple two semiconductors (Cu2O and ZnCdS) to form a type-I heterojunction with high visible light response. The as-synthesized heterojunction was well characterized by the battery techniques, such as TEM, HAADF-STEM elemental mapping, XRD and XPS. The visible light response was higher for composite than individual components, as was also supported by UV–vis DRS. The Cu2O-ZnCdS composite showed a higher visible light-driven photocatalytic H2 production rate (78.5 µmol g–1 h–1). The catalyst was also active for photocatalytic degradation of a model dye-methylene blue (MB)-with a degradation rate constant of 0.079 min−1. The enhanced performance of the Cu2O-loaded ZnCdS catalysts can be ascribed to both factors, such as enhancement of the visible light absorption and the growth of Cu2O-ZnCdS heterojunction. The heterojunction formation facilitates efficient charge separation with smaller charge resistance, as evidenced by transient photocurrent response and electrochemical impedance spectroscopy (EIS) studies. This study strongly indicates that the photocatalytic reactions with this catalyst material are kinetically favoured by coupling the two semiconductors. Graphical abstract

Photocatalytic Hydrogen Production from Pure Water Using a IEF-11/g-C3N4 S-Scheme Heterojunction.

Construction of S-scheme heterojunction offers a promising way to enhance the photocatalytic performance of photocatalysts for converting solar energy into chemical energy. However, the photocatalytic H2 production in pure water without sacrificial agents is still a challenge. Herein, the IEF-11 with the best photocatalytic H2 production performance in MOFs and suitable band structure was selected and firstly constructed with g-C3N4 to obtain a S-scheme heterojunction for photocatalytic H2 production from pure water. As a result, the novel IEF-11/g-C3N4 heterojunction photocatalysts exhibited significantly improved photocatalytic H2 production performance in pure water without any sacrificial agent, with a rate of 576 μmol/g/h, which is about 8 times than that of g-C3N4 and 23 times of IEF-11. The novel IEF-11/g-C3N4 photocatalysts also had a photocatalytic H2 production rate of up to 92 μmol/g/h under visible light and a good photocatalytic stability. The improved performance can be attributed to the efficient separation of photogenerated charge carriers, faster charge transfer efficiency and longer photogenerated carrier lifetimes, which comes from the forming of S-scheme heterojunction in the IEF-11/g-C3N4 photocatalyst. This work is a promising guideline for obtaining MOF-based or g-C3N4-based photocatalysts with great photocatalytic water splitting performance.

Ni(OH)2 Nanosheet as an Efficient Cocatalyst for Improved Photocatalytic Hydrogen Evolution over Cd0.9Zn0.1S Nanorods under Visible Light.

Loading cocatalysts to promote spatial charge separation has been confirmed as an effective method for improving photocatalytic hydrogen production. This article reports that the synthesis of Ni(OH)2/Cd0.9Zn0.1S nanorod photocatalyst is suitable for photocatalytic H2 generation under visible light. It can be proven that the binary photocatalyst exhibits a one-dimensional nanorod morphological structure. Ni(OH)2 nanosheets occupy the top area of Cd0.9Zn0.1S nanorods. The photocatalytic H2 production rate can reach 132.93 mmol·h-1·g-1, which corresponds to an apparent quantum efficiency of up to 76.5% at a wavelength of 460 nm. In addition, the Ni(OH)2 nanosheet can aggregate the light-incited electrons of Cd0.9Zn0.1S, inhibiting the confluence of electrons and holes. The detailed analysis of its mechanism through characterization methods such as photoluminescence and electrochemical measurement shows that the significant improvement in photocatalytic performance derives from the effective spatial separation of photo-induced charge carriers. Therefore, this synthesis strategy of one-dimensional materials may bring new prospects for more efficient, stable, and sustainable photocatalysis for water splitting.

Mixed phase anatase nanosheets/brookite nanorods TiO2 photocatalysts for enhanced gas phase CO2 photoreduction and H2 production

CO2 photoreduction and H2 photocatalytic production reactions have been studied on different TiO2 polymorphs (anatase and brookite) engineered with specific nanocrystal shape. Anatase TiO2 materials of nanosheet morphology and brookite TiO2 of nanorod morphology were developed via a hydrothermal synthesis process. Mixed-phase anatase/brookite TiO2 materials of the above extreme cases were also developed, controlling the phase composition. The materials were fully characterized by a variety of techniques including structural, morphological, textural and electronic properties characterization. N2 physisorption analysis and CO2 adsorption isotherms have shown that minimum amount of brookite phase (i.e. ca. 7 wt%) in the final material improved the textural properties and the CO2 uptake ability. Electron paramagnetic spectroscopy (EPR) provided evidences for improvements in the formation and availability of photogenerated electrons in the mixed-phase materials. CO2 photoreduction was increased by ca. 220% in the optimized mixed-phase anatase/brookite TiO2. Photocatalytic H2 production rates were also improved by ca. 140%. The results in the present study have shown that the TiO2 phase as well as the amount of each TiO2 polymorph plays vital role in photocatalytic efficiency and that the photocatalytic improvement depends greatly on the specific reactions. The new insights provided herein would be of interest for studied focusing on materials shape engineering and phase composition and their effect on activity.

Precise design of TiO2 photocatalyst for efficient photocatalytic H2 production from seawater splitting

The side reactions in seawater and the sedimentation of the photocatalyst in highly concentrated ionic solutions seriously affect the activity and stability of the photocatalyst to split seawater to produce hydrogen. In terms of these problems, we designed the super-hydrophilic mesoporous brookite/anatase TiO2 photocatalyst accordingly. The characterization results of crystal phase and band structure confirmed that the transition from brookite/rutile type I hetero-phase junction to brookite/anatase type II hetero-phase junction. Without any sacrificial agents, the photocatalytic H2 production rate from seawater splitting reached 6.59 mmol g−1 h−1, which was 2.5 times and 2.9 times higher than brookite/rutile TiO2 and anatase/rutile TiO2 (P25), respectively. Meanwhile, it was also 4.4 times, 11.8 times and 36.1 times higher than brookite, anatase and rutile nanoparticles. Furthermore, the contact angle test confirmed the superhydrophilicity of the photocatalyst, mitigating the side reactions induced by Cl− and ensuring the long-term stability (100 h) of the photocatalyst in seawater.

Enhanced interfacial charge transfer by oxygen vacancies in ZnCdS/NiCo-LDH heterojunction for efficient H2 evolution

The elaborate modulation of charge transfer in Z-scheme heterojunctions is of significant importance yet poses a formidable challenge for achieving efficient photocatalytic hydrogen production. The present study reports the fabrication of ZnCdS nanoparticle wrapped by NiCo-layered double hydroxide with enriched oxygen vacancies (ZCS@LDH-Ov) was fabricated, which exhibits enhanced interfacial binding and internal electric field (IEF) in comparison to ZCS@LDH. Under visible-light irradiation, the as-prepared ZCS@LDH-Ov exhibits a superior photocatalytic H2 production rate of up to 2.68 mmol·g−1·h−1, which is approximately 9.24-fold and 2.68-fold of the pristine ZnCdS and ZCS@LDH, respectively. The stability of the photocatalyst after 5 cycles is obviously enhanced, with ZCS@LDH exhibiting a remaining hydrogen evolution reaction (HER) rate of 52.7 % and ZCS@LDH-Ov demonstrating an impressive remaining rate of 98.2 %. The Z-scheme facilitates rapid charge transfer and efficient separation, thereby enhancing the catalytic activity for HER. The excellent recyclability of ZCS@LDH-Ov is primarily attributed to enhanced photo-corrosion resistance of ZnCdS, which can be ascribed to the efficient transfer of photo-generated holes through a rapid interfacial charge pathway.

Modulating electronic structure and sulfur p-band center by anchoring amorphous Ni@NiSx on crystalline CdS for expediting photocatalytic H2 evolution

Photocatalytic water splitting is a prospective approach to address the energy and environmental challenges. Herein, an amorphous Ni@NiSx cocatalyst has been fabricated and simultaneously assembled onto CdS to form amorphous-crystalline Ni@NiSx-CdS photocatalyst via a partial reduction strategy. Comprehensive experiments and theoretical calculations demonstrate that the synergistic effects between the electronic coupling of amorphous-crystalline interface and the gradient work function variation induced by Ni nanocluster encapsulation achieve the deeper downshift of the S p-band center to optimize H* intermediate adsorption, enhance charge extraction ability though Schottky junction and lower H* adsorption Gibbs free energy (ΔGH*). Accordingly, the optimal Ni@NiSx-CdS photocatalyst delivers a remarkable photocatalytic H2 production rate of 78.7 mmol·g−1·h−1 with an apparent quantum efficiency (AQE) of 36.74% at 420 nm, which is approximately 18.3 and 1.5 times than that of CdS and NiSx-CdS, respectively. This work offers a novel insight into the development of amorphous nanocomposite cocatalysts for promoting solar-to-H2 energy conversion.

Probing the role of H-ZSM-5 zeolite in the hydrogen evolution performance of graphitic carbon nitride

Graphitic carbon nitride (CN) hold great promise as a photocatalyst for generating hydrogen energy via water splitting, owing to its remarkable ability to respond to visible light and its strong reduction capacity. However, the photocatalytic water splitting for H2 evolution performance of pure CN was impeded by its low surface area, inadequate hydrophilicity, and unsatisfactory photoelectric conversion efficiency. Here we tackled these challenges by synthesizing a series of CN/H-ZSM-5 composites with varying amount of H-ZSM-5 zeolite using a straightforward thermal copolymerization method. The contact angle and N2 adsorption-desorption measurements confirmed that the incorporated hydrophilic and porous H-ZSM-5 zeolite contribute to increased surface area and improved hydrophilicity of the CN/H-ZSM-5 composites. Meanwhile the resulting CN/H-ZSM-5 composites exhibited significant separation and migration enhancement of photoexcited charge carriers. Consequently, the optimized CN/H-ZSM-5 composite, containing 50 mg of H-ZSM-5 zeolite, demonstrated 13 times increase in photocatalytic H2 production rate than that of pure CN. This work not only provided a competitively universal approach on the design of high-efficiency CN based photocatalyst, but also clarified the role of H-ZSM-5 zeolite in the H2 evolution enhancement.

Construction of S-scheme heterojunction catalytic nanoreactor for boosted photothermal-assisted photocatalytic H2 production

Reasonable design of heterojunction band structure and strengthening of the photothermal effect is an important method to promote the photothermal-assisted photocatalytic H2 production activity of photocatalysts. Herein, a composite material named as Co3O4/CNNVs S-scheme heterojunction nanoreactor was constructed by loading Co3O4 nanoparticles on the surface of g-C3N4 nanovesicles (CNNVs) through a simple hydrothermal method and used to achieve efficient photothermal-assisted photocatalytic H2 production. In the absence of Pt as a cocatalyst, Co3O4/CNNVs-22.5 exhibited a photocatalytic H2 production rate up to 772.9 μmol g-1h−1 under irradiation with a 300 W Xenon lamp, which is much higher than that of pure CNNVs (15.5 μmol g-1h−1). In the Co3O4/CNNVs photothermal-assisted photocatalytic system, the synergistic effect of the strong photothermal effect of Co3O4 nanoparticles and the thermal insulation effect of hollow CNNVs nanoreactor was shown to be the main reasons for promoting the surface temperature increase of the heterojunction photocatalyst, which effectively facilitates the separation and transfer of photo-generated carriers, thus increasing the photocatalytic H2 production. In addition, the S-scheme heterojunction formed between Co3O4 and CNNVs optimize the charge transfer path. This work presents a reasonable design of highly efficient photocatalyst with a S-scheme heterojunction nanoreactor for the photothermal-assisted photocatalysis.

Amorphization-induced reverse electron transfer in NiB cocatalyst for boosting photocatalytic H2 production

Regulating the electron density distribution of active sites to accelerate catalytic process is of great significance to explore high-efficiency cocatalysts for photocatalytic hydrogen production. In this work, a novel strategy of amorphization-induced reverse electron transfer is proposed to optimize the electronic structure of Ni active site in nickel boride (NiB) cocatalyst to promote the photocatalytic hydrogen-production activity of TiO2. Herein, the NiB nanodots (0.5–1 nm) with an amorphous structure can perfectly be anchored onto TiO2 surface via a novel-designed light-induced route. The resulting amorphous-NiB/TiO2 sample achieves the photocatalytic H2-production rate of 2334.0 μmol h−1 g−1, which is 1.8 times higher than that of the traditional crystalline-NiB/TiO2 photocatalyst. The experimental and theoretical investigations confirm that the amorphization of NiB can induce the reverse electron transfer from B to Ni, which can promote the hydrogen desorption process of the Ni active site to boost the H2-production efficiency. This work paves a new way for active site optimization and delivers in-depth insights for the exploration of high-efficient hydrogen-production cocatalysts.

Photocatalytic Biohydrogen Production Using ZnO from Aqueous Glycerol Solution with Aid of Simultaneous Cu Deposition

Biodiesel has gained a great deal of attention as a new sustainable energy alternative to petroleum-based fuels. The subsequent increased biodiesel production requires new utilization of glycerol, which is a byproduct of biodiesel synthesis. Photocatalytic biohydrogen generation using ZnO with the aid of simultaneous deposition of copper from an aqueous biomass-derivative glycerol solution was investigated. The effects of the concentration of glycerol solution, Cu ion concentration, and reaction temperature on biohydrogen generation were investigated. The photocatalytic biohydrogen production rate increased as the concentration of aqueous glycerol solution increased, and the observed data could be fitted to the Langmuire–Hinshelwood kinetic models. The photocatalytic H2 production efficiency with ZnO could be significantly improved by simultaneous Cu deposition. The photocatalytic biohydrogen production rate was dependent on temperature, and increased as the temperature increased. Under the optimal conditions, the photocatalytic H2 production rate was 72 µmol h−1 g−1 from the aqueous biomass-derivative glycerol solution. Possible mechanisms for the oxidation of glycerol solution and photocatalytic hydrogen generation were proposed.

Self-optimized H-adsorption affinity of CuRu alloy cocatalysts towards efficient photocatalytic H2 evolution

In addition to the electron transfer, the appropriate H-adsorption affinity of active centers on the metal cocatalyst surface is quite important for high hydrogen-production activity of cocatalyst-modified photocatalysts. The typical Cu and Ru metal cocatalysts clearly exhibit a weak Cu–H bond and a strong Ru–H bond, respectively, resulting in limited activity for photocatalytic H2 evolution. In this work, an ingenious strategy of self-optimized H-adsorption affinity in CuRu alloy cocatalyst is developed to simultaneously reinforce the Cu–H bond and weaken the Ru–H bond by the intrinsic electron transfer from Cu to Ru atom. The CuRu alloy nanoparticles (2–3 nm) were deposited on the TiO2 surface to prepare CuRu/TiO2 through a one-step photoreduction method. Photocatalytic tests exhibited that the highest H2-production rate of CuRu/TiO2 photocatalyst reached up to 5.316 mmol h–1 g–1, which was 24.80, 1.86, and 2.60 times higher than that of the TiO2, Cu/TiO2, and Ru/TiO2, respectively. Based on the characterization results and theoretical calculations, the CuRu alloy cocatalyst exhibits excellent self-optimized H-adsorption affinity via the spontaneous electron transfer from Cu to Ru atom, which can greatly accelerate the photocatalytic H2-production rate of TiO2. This work provides a feasible idea for the self-optimized H-adsorption affinity of metal active sites in the photocatalytic H2-generation field.

High-performance visible-light-driven MoS2/CdZnS nanorods for photocatalytic hydrogen production by water splitting

In this study, CdZnS nanorods modified with MoS2 nanosheets were prepared by a hydrothermal method. The CdZnS nanorods were optimized by varying Zn amounts according to their photocatalytic H2 production performance. The Cd:Zn = 9:1 (CZS) sample exhibits the highest photocatalytic H2 production rates among various samples. MoS2 nanosheets were loaded on the surface of the Cd:Zn = 9:1 sample by a sonication method. 6 wt% MoS2 decoration (M6-CZS) enables to achieve the highest H2 production rate (75.89 mmol g−1 h−1) among the composites, which was 11.3 times higher than that of pristine CZS. The enhanced mechanism was analyzed with the aid of electrochemical experiments. The results reveal that M6-CZS exhibit higher photocurrent density, increased donor density, lower charge transfer resistance and recombination rate, which are the reasons for the improved photocatalytic performance. This study sheds light on the design of novel composites as excellent visible-light-driven photocatalysts for solar‑hydrogen energy conversion.

Rational Design of Vinylene-Linked Covalent Organic Frameworks for Modulating Photocatalytic H2 Evolution.

Vinylene-linked covalent organic frameworks (COFs) have attracted enormous attention for photocatalytic H2 evolution from water because of their fully conjugated structures, high chemical stabilities, and enhanced charge-carrier mobilities. In this work, two novel vinylene-linked COFs with tuned cyano contents were successfully synthesized and then employed as photocatalysts for H2 generation. Notably, the photocatalytic H2 production rate of the COF with the higher cyano content reached 73 μmol h-1 under visible light irradiation, which is 2.4 times higher than that with the lower content (30 μmol h-1 ). Both the experimental and computational results demonstrated that the rational design incorporating cyano groups into COF skeletons could precisely tune the corresponding energy levels, expand the visible-light absorption, and improve the photoinduced charge separation. This work not only provides a simple method for modulating the photocatalytic activities of COFs at the molecular level, but also affords interesting insights into the relationship between their structures and photocatalytic performance.

Linker Engineering of Sandwich-Structured Metal-Organic Framework Composites for Optimized Photocatalytic H2 Production.

While the microenvironment around catalytic sites is recognized to be crucial in thermocatalysis, its roles in photocatalysis remain subtle. Herein, a series of sandwich-structured metal-organic framework (MOF) composites, UiO-66-NH2 @Pt@UiO-66-X (X means functional groups), have been rationally constructed for visible-light photocatalytic H2 production. By varying -X groups of UiO-66-X shell, the microenvironment of Pt sites and photosensitive UiO-66-NH2 core can be simultaneously modulated. Significantly, the MOF composites with identical light absorption and Pt loading present distinctly different photocatalytic H2 production rates, following -X group sequence of -H > -Br > -NA (naphthalene) > -OCH3 > -Cl > -NO2 . UiO-66-NH2 @Pt@UiO-66-H demonstrates H2 production rate up to 2708.2μmol g-1 h-1 , ∼222 times that of UiO-66-NH2 @Pt@UiO-66-NO2 . Mechanism investigations suggest that the variation of -X group can balance the charge separation of UiO-66-NH2 core and proton reduction ability of Pt, leading to the optimal activity of UiO-66-NH2 @Pt@UiO-66-H at the equilibrium point. This article is protected by copyright. All rights reserved.

TiO2–x@C/MoO2 Schottky junction: Rational design and efficient charge separation for promoted photocatalytic performance

Limited solar light harvesting, sluggish charge transfer kinetics, and inferior affinity for adsorbed hydrogen species (H*) severely restrict the photocatalytic hydrogen generation activity of TiO2 photocatalysts. Herein, we present a novel TiO2–x@C/MoO2 Schottky junction prepared via a simple one-step in situ phase-transition-regulation strategy. Crucially, the abundant oxygen vacancies in TiO2–x@C/MoO2 narrow the bandgap and introduce defects to improve the photoresponse. The strongly bonded carbon layer not only serves as a fast charge-transport channel to improve the interlayer charge transfer efficiency but also protects oxygen vacancies from oxidation. Moreover, the Schottky barrier effectively impairs the recombination of electrons and holes and promotes the utilization of photogenerated electrons. Furthermore, the MoO2 cocatalyst optimizes the Gibbs free energy for H2 evolution. As a result of the favorable synergy, the resulting TiO2–x@C/MoO2 presents a significantly enhanced photocatalytic H2 production rate of 506 μmol g−1 h−1 compared to those of TiO2–x and TiO2–x@C (125.5- and 15.8-times larger, respectively). Moreover, outstanding stability over 27 h was achieved because of the protection provided by the surface carbon layer. This ingenious design and facile synthetic strategy offer exciting avenues for the design of strongly coupled Schottky junction photocatalysts for efficient solar-to-chemical conversions.