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The visible‐light responsive semiconductor carbon nitride (C3N4) exhibits suitable electronic band structure, rich sources of precursors, and high stability, which is exploited to satisfy energy demands. However, the photocatalytic efficiency of C3N4 is limited because of its low surface area and low separation and transfer efficiency of charge carriers. As Z‐scheme strategy can effectively help C3N4 overcome its instinct shortage, this review will outline the recent significant progress on the development of C3N4‐based all‐solid Z‐scheme photocatalysts for energy‐conversion applications including water splitting and CO2 reduction. In the beginning, the fundamental principles of Z‐scheme will be introduced, especially for all‐solid‐state system. Then, the comprehensive account of the development of C3N4‐based Z‐scheme photocatalysts are discussed. Finally, perspectives on the challenges and future directions at the forefront of Z‐scheme photocatalysts are provided. [ABSTRACT FROM AUTHOR]

A novel method for starch modification is investigated. Starch is highly cross linked by glow discharge plasma, without the assistance of conventional chemical agents, thus avoiding any environmental concerns. An energy-charge-transfer mechanism is suggested for the function of plasma. This process could be useful for the production of large quantities of modified starch. [Copyright &y& Elsevier]

Quantum dot (TiO2) self-decorated and defect-free anatase nanosheets were fabricated by a long-time hydrothermal strategy and subsequent defect healing. Such decoration provides a new and effective charge transfer pathway over the nanosheet surface, leading to remarkably high photoactivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@Pt decorated Zn-CdS composites are fabricated for promoted charge separation. • Photodeposition leads to formation of Au-S bond and act as charge transfer channel. • The composites show synergetic effect of SPR and charge transfer channel. • Surface Pt serves active sites for rapid surface reaction. • Au@Pt/Zn-CdS exhibits lower charge transfer resistance and higher PEC activity. Photoelectrochemical (PEC) water splitting is a promising approach to solve the current energy and environmental crises. Herein, we developed a "one stone, two birds" strategy to construct Au@Pt decorated ZnO/CdS heterojunctions (ZCAP) with Au-S bond and surface plasmon resonance (SPR) effect for promoted PEC water splitting. The optimized ZCAP structure exhibited the highest photocurrent density of 4.23 mA/cm2 at 1.23 V vs. RHE and hydrogen evolution rate of 72.3 μmol·cm−2·h−1, which is magnitude higher than pure ZnO. In-depth investigations indicate that SPR effect can afford hot electrons, whereas Au-S bonds over interface act as transmission bridge for facilitated electron transfer, the synergy of them achieves efficient charge separation and light utilization. Meanwhile, surface Pt nanoparticles serve as active sites for rapid charge transfer and promoted surface reaction. This article illustrates that the synergy of SPR and electron transfer bridge is an efficient strategy for promoted PEC performance. [ABSTRACT FROM AUTHOR]

The work function of BiVO 4 is modulated from smaller to larger than that of PCN by controlling the oxygen vacancy, which switches the direction of interfacial band bending in BiVO 4 /PCN heterojunction. Accordingly, the photoinduced charge transfer mechanism is changed from type-II to direct Z-scheme for superior solar-driven pure water splitting. [Display omitted] Nature-inspired artificial Z-scheme photocatalyst offers great promise in solar overall water splitting, but its rational design, construction and interfacial charge transfer mechanism remain ambiguous. Here, we design an approach of engineering interfacial band bending via work function regulation, which realizes directional charge transfer at interface and affords direct Z-scheme pathway. Taking BiVO 4 as prototype, its oxygen vacancy concentration is reduced by slowing down the crystallization rate, thereby changing the work function from smaller to larger than that of polymeric carbon nitride (PCN). Consequently, the photoinduced charge transfer pathway of BiVO 4 /PCN is switched from type-II to Z-scheme as evidenced by synchronous illuminated X-ray photoelectron spectroscopy (XPS) and femtosecond transient absorption spectroscopy. Specifically, the direct Z-scheme BiVO 4 /PCN shows superior photocatalytic performance in water splitting. This work provides deep insights and guidelines to constructing heterojunction photocatalysts for solar utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • A piezotronic ZnO homojunction via defects modulation is designed. • The unique ZnO-based photoanode has piezoelectric effect and p-n homojunction. • This homojunction can avoid lattice mismatching and suppress carrier recombination. • The piezo-phototronic effect can enhance electric field of space charge region. • The piezo-photoelectrochemical activity is 2.1-times higher than pure ZnO. Homojunction is a viable alternative strategy to realize excellent charge separation for enhancing photoelectrocatalytic performance. However, the feasible regulation of the homojunction interface remains challenging. Herein, a ZnO n-p homojunction with the piezotronic effect is constructed via an in-situ solvothermal method for enhancing photoelectrocatalytic activity. ZnO nanorods are transformed from n-type to p-type ZnO nanoparticles with zinc vacancies, leading to the n-p homojunction. The optimal NPZ-36 exhibits a superior photocurrent density of 1.56 mA/cm2 at 1.23 V vs. RHE and a high incident photon to current conversion efficiency of 75 % at 360 nm. Impressively, with the merits of inherent piezoelectric and photocatalytic properties of wurtzite ZnO, the piezoelectric-enhanced photoelectrochemical activity originates from the simultaneous promotion of bulk charge transfer and interfacial charge separation in ZnO n-p homojunction. The photocurrent density of NPZ-36–900 can reach to 2.02 mA/cm2 under the stirring rate of 900 rpm, which is 2.1 times higher than that of pure ZnO photoanode. [ABSTRACT FROM AUTHOR]

ZnO p-n homojunctions with tunable p/n ratio was fabricated by decorating n-ZnO nanoparticles on p-ZnO leaves and shows excellent performance in charge separation and photocatalysis. • ZnO p-n homojunction was fabricated by decorating n-type ZnO NPs on p-type ZnO. • ZnO p-n homojunction is abundant in both V o and V Zn simultaneously. • The p-n homojunction shows high efficiency in charge transfer and separation. • ZPN-5 with suitable p/n ratio shows the highest photocatalytic and PEC performance. Construction of junctions between semiconductors is an effective way to promote charge separation and thus improve the photoelectrochemical and photocatalytic performance. Specifically, p-n homojunctions are more efficient due to the larger driving force and lower transfer barrier over the interface. Herein, we fabricated ZnO p-n homojunctions by depositing n-type ZnO nanoparticles (with oxygen vacancy) on the surface of p-type ZnO (with metal vacancy). The structures of the composite were well characterized by TEM, XRD, TG, XPS and EPR analyses. Meanwhile, both the "V-shaped" Mott-Schottky plots and anodic shift of onset potentials confirmed the existence of p-n homojunction, which exhibits much more efficient charge transfer and separation than pure type ZnO as indicated by PL and EIS measurements. As a result, p-n homojunction exhibited activity of 3.2-fold and 3.3-fold higher than pure p-ZnO in photodegradation of phenol and as photocathode in photoelectrochemical water splitting, respectively. This work provides a new strategy for the design and fabrication of highly efficient photocatalysts with promoted charge separation. [ABSTRACT FROM AUTHOR]

Photocatalytic water oxidation suffers from sluggish kinetics and remains the bottleneck for water splitting. Here, using CeO 2 nanorods as model photocatalyst we studied the critical role of oxygen vacancies in photocatalytic water oxidation. First CeO 2 nanorods with similar morphology but different concentration of oxygen vacancies were fabricated by one-step hydrothermal method with in-situ reducing treatment. The optical absorption, charge transfer efficiency, and photocatalytic activity in oxygen generation were found closely dependent on the concentration of oxygen vacancies. Then density functional theory calculations were conducted to unveil the role of oxygen vacancies and understand the water oxidation mechanism. It was found the presence of oxygen vacancies narrows the bandgap and modulates the electronic structure for accelerating the charge transfer, in good agreement with the experimental observations. The overall oxygen generation pathway was screened and the oxygen vacancies were found to lower the barrier energy for the rate limiting step of O O bond formation and restrain the reverse reaction of O and H, thus the O 2 generation kinetics on oxygen-defective CeO 2 are improved significantly. This study provides in-depth understanding on the critical role of oxygen vacancies in photocatalytic water oxidation and is helpful for designing highly efficient photocatalyst to overcome the bottleneck of water splitting. [ABSTRACT FROM AUTHOR]

TiO 2 has been intensively investigated for decades as the most important photocatalyst, but its photoactivity still needs further improvment. TiO 2 surface and interface are vital in photocatalysis because it is where the photo-excitation, charge transfer and subsequent photoreaction take place. Surface and interface control has been demonstrated as very effective approach to synthesize highly efficient TiO 2 . Here we highlight our recent work as well as the state-of-the-art in controlling of TiO 2 surface and interface including facet growth, surface decoration and surface adsorption that leads to better photocatalytic performance. It is expected to provide some guidelines for rational design and fabrication of highly efficient TiO 2 -based materials for photocatalysis. [ABSTRACT FROM AUTHOR]

• Direct Z-scheme ZnO-WO 3- x was constructed by in-situ solvothermal treatment. • Suitable band structure and Fermi level drive the formation of Z-scheme structure. • Stirring leads to piezoelectric polarization of ZnO, and enhances Z-scheme effect. • Zn-W-5 shows very high piezoelectric-photoelectrochemical activities. Photosynthesis with Z-scheme charge transfer has been recognized as an efficient pathway to achieve solar-energy conversion. Herein, the all-solid-state direct Z-scheme ZnO-WO 3-x nanorod arrays were synthesized by in-situ solvothermal treatment for highly piezoelectric (PE)-photoelectrochemical (PEC) water splitting. The chemical bonding between WO 3-x and ZnO via W-O-Zn and the inherent band structures/Fermi levels drive the formation of direct Z-scheme charge-transfer pathway. Importantly, the optimized structure (Zn-W-5) shows higher PEC activities with high photocurrent density of 2.39 mA/cm2 at 1.23 V vs. RHE, which is 2.13 times higher than pure ZnO. Surprisingly, the obvious PE polarization of ZnO increases its Fermi level toward conduction band and significantly enhances Z-scheme effect between ZnO and WO 3-x. Especially, the best sample (Zn-W-5-1000 rpm) shows a photocurrent of 3.38 mA/cm2 at 1.23 V vs. RHE, which is 3.02 times higher than pure ZnO. This work provides a facile PE polarization approach for enhancement of Z-scheme charge-transfer process. [ABSTRACT FROM AUTHOR]

• All-in-one Pt·Ni(OH) 2 /C 3 N 4 photocatalyst realizes one-step overall water splitting. • Pt·Ni(OH) 2 /C 3 N 4 achieves a prominent AQE of 4.2% at 420 nm and excellent stability. • Both H 2 O activation and charge transfer are dramatically enhanced. • The backward recombination of H 2 and O 2 is suppressed. Overall water splitting is vital in solar-hydrogen conversion. In addition to charge separation, the regulation of surface kinetics and suppression of backward reaction become particularly crucial. Herein, an all-in-one Pt·Ni(OH) 2 /C 3 N 4 photocatalyst is proposed by integrating Pt@Ni(OH) 2 composited nanowires and isolated Pt clusters on C 3 N 4. In this heterostructure, Pt@Ni(OH) 2 with rich coordinatively unsaturated sites effectively boost O 2 evolution, and Pt-O-Ni interaction retards O O bond cleavage thus inhibiting backward H 2 O regeneration. Meanwhile isolated Pt forms an Schottky junction with C 3 N 4 for electron transfer and proton reduction. Consequently, Pt·Ni(OH) 2 /C 3 N 4 achieves stoichiometric water splitting with H 2 /O 2 evolution of 1330/632 μmol g−1 h−1, and an outperforming AQE of 4.2% at 420 nm. Our work manifests that accelerating charge migration, inhibiting backward reaction and tuning surface kinetics are dominant in water splitting, for which a rational design of robust redox pathways is necessary. [ABSTRACT FROM AUTHOR]

• MnO x -decorated 3D porous C 3 N 4 is fabricated by NaCl-templated method. • C 3 N 4 possesses donor–acceptor system by Na ions and cyano groups. • MnO x modulate holes transfer and provide oxidation sites. • C 3 N 4 shows quick charge separation and stronger reduction capability. • C 3 N 4 achieves 18-fold higher H 2 production rates of bulk C 3 N 4 under visible light. Carbon nitride is an intriguing visible-light photocatalyst for H 2 production but suffers from low surface area and fast charge recombination. Here, we report a simple yet efficient approach to fine tune the porous structure, modify the electronic structure and carrier behaviors of C 3 N 4 through in-situ growth of MnO x by NaCl template-assisted strategy. This NaCl template method simultaneously constructs 3D porous structure for high surface area, induces Na coordination with N atoms and accompanying cyano group to form an internal donor-acceptor system for efficient charge transfer and separation. Along with the MnO x growth, the band gap of C 3 N 4 is narrowed for stronger visible light absorption and the conduction band level is negatively shifted for stronger reduction capability. Thus, the resulted C 3 N 4 (MSCN) shows much improved activity of about 18 times higher than bulk C 3 N 4 in photocatalytic hydrogen evolution reaction under visible light irradiation. [ABSTRACT FROM AUTHOR]