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LaTiO2N is a promising narrow‐bandgap semiconductor photocatalyst that shows great promise for water redox reactions. However, its performance is often hindered by fast photocarrier recombination events. Herein, LaTiO2N mesoporous single crystals (MSCs) are successfully fabricated via a topotactic conversion route by using the Ruddlesden–Popper compound NaLaTiO4 as the precursor. The LaTiO2N MSCs are characterized by high crystallinity, abundant mesopores, no grain boundaries (GBs), and exposure of (010) and (101) crystal facets. A facet‐assisted photocarrier separation mechanism is identified for these LaTiO2N MSCs which contributes to the much better photocarrier separation than conventional counterparts. By loading proper cocatalysts, LaTiO2N MSCs serve as an efficient photocatalyst for water‐splitting half‐reactions and are capable of photocatalyzing overall water‐splitting reactions, delivering an impressive apparent quantum efficiency (AQE) as high as 65.07% at 420 ± 20 nm for O2‐evolution and a solar‐to‐hydrogen (STH) efficiency as high as 0.012% for solar‐driven overall water splitting. These findings not only highlight the grain‐boundary‐free MSCs with peculiar crystal‐facet exposure as highly active photocatalysts for particulate photocatalysis but also provide a rational design approach for developing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) with low-dimensional, deformable haloplumbate secondary building units (SBUs) are an emerging class of intrinsic white-light emitters combining advantageous properties of both MOFs and lead perovskites. Herein, we have successfully synthesized two MOFs with haloplumbate SBUs occupying an extremely high degree of structural strain with local zigzag Pb–X–Pb–X (X = Cl/Br) connectivity located in single-stranded helices. Thus, the electron–phonon coupling in the deformable SBUs affords intrinsic white-light emission and moderately high external photoluminescence quantum efficiencies of 12–15%, superior to our previously reported MOFs. Moreover, the excellent photocarrier diffusion properties of lead perovskites have been successfully incorporated into the MOFs with high chemical robustness in moisture (up to 90% relative humidity, RH). [ABSTRACT FROM AUTHOR]

Mg modifications over BaTaO 2 N reduce Ta4+ defects concentration, contributing to much improved photocatalytic activities for water oxidation reactions. • Mg modifications strengthen Ta-O/N bonds in BaTaO 2 N. • Ta4+ defects concentration decreases in Mg modified BaTaO 2 N. • Photocatalytic performance is much improved after Mg modifications. • Band edges are positively shifted in Mg modified BaTaO 2 N. • Mg contributes to improved interactions between BaTaO 2 N and CoO x. BaTaO 2 N owns a promising band gap of 1.8 eV and suitable band edge positions but generally exhibits poor photocatalytic activity for water splitting reactions. In this work, we have modified BaTaO 2 N by introducing Mg to the B site of perovskite lattice to form a new compound, i.e. BaTa 0.95 Mg 0.05 O 2+x N 1−y. This modification results in an alteration to a number of important parameters such as unit cell size, nitrogen content, optical absorption and microstructures etc. More importantly, Mg modifications are responsible for stronger Ta-O/N bonds, lower Ta4+ defects concentration and positively shift of band edge positions, which in turn contribute to high photocatalytic activities for water oxidation reactions. Apparent quantum efficiency as high as 2.59% has been realized at 420 ± 20 nm, being the highest for BaTaO 2 N reported to date under similar conditions. Further photoelectrochemical analysis confirms better charge utilizations in Mg modified BaTaO 2 N. [ABSTRACT FROM AUTHOR]

With a light absorption up to 740 nm, BaNbO 2 N is promising for solar water splitting but normally owns a low activity due to a high defect concentration. Here, Mg is adopted as a dopant to modify the BaNbO 2 N. The presence of Mg not only reduces the defect concentration and enhances surface hydrophilicity but also tunes the bandgap as well as the band edge positions. These modifications greatly promote the charge separation and transfer of BaNbO 2 N, boosting the photocatalytic activities for O 2 -evolution reactions. An apparent quantum efficiency of 1.65 % at 420 ± 20 nm has been attained for Mg modified BaNbO 2 N. Overall water splitting at a stable gas-evolution rate (∼ 2.0 μmol·h−1 for H 2 and ∼ 1.0 μmol·h−1 for O 2) has been realized by integrating Mg-modified BaNbO 2 N into a Z-scheme system. These findings justify Mg as an effective dopant to modulate the photocatalytic behavior of Nb-based perovskite oxynitrides. [Display omitted] • Mg doping suppresses the Nb4+ defects and enhances surface hydrophilicity of BaNbO 2 N. • Mg doping tunes the bandgap and the band edge positions of BaNbO 2 N. • Mg doping improved charge separation and the photocatalytic activity of BaNbO 2 N. • An AQE as high as 1.65 % at 420 ± 20 nm has been recorded for OER. • Z-scheme overall water splitting is realized using Mg-modified BaNbO 2 N. [ABSTRACT FROM AUTHOR]

LaTiO 2 N is modified by Mg doping to construct solid solution series, i.e., LaTi 1−x Mg x O 2+y N 1−y (0 ≤ x ≤ 0.5). This modification effectively decreases the defect concentration (particularly bulk Ti3+ species and anion vacancies), increases the surface hydrophilicity, positively shifts the valence band top albeit it also enlarges the bandgap and induces Ti/Mg ordering when x ≥ 0.2. These competitive tensions render an optimal composition at LaTi 0.9 Mg 0.1 O 2+y N 1−y (x = 0.1) where both a low defect concentration and a disordered state of Ti/Mg can be reached, demonstrating much-improved photocarrier separation and exceptional photocatalytic activity with apparent quantum efficiency as high as 13.02 % at 420 ± 20 nm for O 2 -evolution. Overall water splitting (H 2 /O 2 molar ratio = 2/1) with good recycling stability has been realized by integrating LaTi 0.9 Mg 0.1 O 2+y N 1−y into a Z-scheme system. These findings justify the efficacy of Mg as a useful modulator to improve the photocatalytic performance of metal oxynitrides. [Display omitted] • Solid solution series LaTi 1−x Mg x O 2+y N 1−y (0 ≤ x ≤ 0.5) have been synthesized. • Mg doping modifies a number of important properties of LaTiO 2 N. • Optimal composition is found at x = 0.1 with exceptional photocatalytic activity. • An AQE as high as 13.02 % at 420 ± 20 nm has been attained for O 2 -evolution. • Z-scheme overall water splitting is achieved using Mg-modified LaTiO 2 N. [ABSTRACT FROM AUTHOR]

Nanostructured Cu doped SrTiO 3 with visible-NIR light response was successfully synthesized for aerobic and anaerobic oxidation of alcohols. The resulted Cu doped SrTiO 3 gave efficient activity for the selective photo-oxidation of benzyl alcohols with AQE of 43.22% and 14.47% at 420 nm and 700 nm, respectively. [Display omitted] • Highly crystallized nanostructured Cu doped SrTiO 3 were successfully synthesized. • Introduction of copper and oxygen vacancies results in visible-near-infrared response. • AQE at 420 nm and 700 nm reach up to 43.22% and 14.47%, respectively. • Alcohols can be selectively converted into corresponding carbonyl compounds. • Cu doped SrTiO 3 is NIR-light-active photocatalyst for selective oxidation of alcohols. Cu doped SrTiO 3 (Cu-STO) has been synthesized and investigated as the photocatalyst for selective alcohol oxidation under mild condition. Cu-STO samples demonstrate intense absorption to visible light and near-infrared light. Using water as the reaction solvent, Cu-STO samples can efficiently oxidize benzyl alcohol (BA) into benzyl aldehyde under both anaerobic and aerobic conditions with high selectivity. In aerobic condition, an apparent quantum efficiency as high as 43.22% at 420 nm has been reached for benzyl alcohol oxidation. More strikingly, the apparent quantum efficiency remains as high as 14.47% even at 700 nm, being the highest one reported to date under similar conditions. Further analysis indicates Cu dopants induces abundant oxygen vacancies and introduces interband springboard into SrTiO 3 , which effectively extend the light response of SrTiO 3 to the visible and NIR region and enhance the separation of charge carriers, being critical to the highly selective and efficient conversion of alcohols. [ABSTRACT FROM AUTHOR]

Formation of solid solutions between LaTaON 2 and SrZrO 3 tailors many important parameters of LaTaON 2 such as band gap, band edge positions, structural distortions, defects concentration and surface hydrophilicity etc. which in turn, contribute to much enhanced photocatalytic activities for water oxidation reactions. • Complete solid solutions have been built between LaTaON 2 and SrZrO 3. • Band gap become tunable in solid solutions. • Structural distortions and defects' concentration are mitigated in solid solutions. • Surface hydrophilicity of LaTaON 2 is improved by introducing SrZrO 3. • Much enhanced photocatalytic activities were realized in solid solutions. Complete solid solutions between LaTaON 2 and SrZrO 3 , i.e. (LaTaON 2) 1−x (SrZrO 3) x (0 ≤ x ≤ 1) have been built which are very useful in tailoring many important parameters of LaTaON 2. Band gap of LaTaON 2 becomes tunable by controlling the level of solid solutions with SrZrO 3. Structural distortions, defects (e.g. Ta4+ species) concentration and surface hydrophilicity of LaTaON 2 are largely improved by introducing SrZrO 3 in the structure. These modifications contribute to much enhanced photocatalytic activities of solid solutions for oxygen production which clearly outperform pristine LaTaON 2 under visible light illumination. Apparent quantum efficiency as high as 0.87% at 420 ± 20 nm was achieved at (LaTaON 2) 0.6 (SrZrO 3) 0.4 (x = 0.4). Further analysis suggest that introducing SrZrO 3 results in realignment of band edge positions of LaTaON 2 so as to be more appropriate for water splitting reactions. [ABSTRACT FROM AUTHOR]

A triazine-based conjugated microporous polymer with ideal optical band gap, which was designed and synthesized through a simple, efficient, metal-free catalyzed approach, has been demonstrated to exhibit good performance for photocatalytic visible-light driven hydrogen generation. • A novel metal-free approach was used to synthesize conjugated microporous polymer. • Band gap is narrowed through introduction of rationally designed D A type monomer. • Rich nitrogen atoms and porous morphology help to improve the photocatalytic property. • This polymer exhibits a high H 2 evolution rate under visible light illumination. Conjugated microporous polymers (CMPs) are an emerging class of promising photocatalysts because of their large specific surface areas and adjustable optical band gaps. To avoid the metal contamination, metal-free synthetic procedure for making CMPs for photocatalytic water splitting are highly desired. Herein, we designed and synthesized two triazine-based conjugated microporous polymers P1 and P2 through a simple, efficient, metal-free catalyzed approach. Through linking donor-acceptor (D-A) type pyrazole-benzothiadiazole-pyrazole light-absorbing units by triazine units, P1 has an ideal optical band gap of about 2.3 eV and exhibits a high H 2 evolution rate (HER) of 50 μmol h−1 under visible light illumination (λ ≥ 420 nm) and apparent quantum efficiency (AQE) as high as 3.58% at 420 ± 20 nm. In contrast, by replacing electron-neutral benzene instead of electron-withdrawing benzothiadiazole, P2 shows obvious hypochromatic shift in the absorption and large optical band gap of about 2.9 eV, as well as poor photocatalytic property. [ABSTRACT FROM AUTHOR]

More than 2.6 eV band gap reductions were realized on a wide band gap semiconductor Mg 4 Ta 2 O 9 by nitrogen doping. The nitrogen doped Mg 4 Ta 2 O 9 , i.e. Mg 4 Ta 2 O 9-x N y , shows promising photocatalytic activities for both water reduction and oxidation under visible light illumination (λ ≥ 400 nm). • 2.64 eV band gap reductions have been achieved on Mg 4 Ta 2 O 9 doped with N. • Surface hydrophilicity has been improved by N doping. • Mg 4 Ta 2 O 9-x N y is visible light active for photocatalytic H 2 and O 2 production. • Flat band potential of Mg 4 Ta 2 O 9 is nearly unchanged after N doping. • N doping leads to uplift of valence band edge. Band gap engineering on wide band gap semiconductor photocatalysts is of critical significance in improving their solar energy utilization. Here, we have successfully realized large band gap reduction and visible light photocatalytic water splitting on a wide band gap semiconductor Mg 4 Ta 2 O 9 by nitrogen doping. More than 2.6 eV reductions in band gap have been achieved after doping nitrogen into Mg 4 Ta 2 O 9 , which strikingly red-shifts its absorption edge from less than 300 nm to as far as 600 nm. The nitrogen doped Mg 4 Ta 2 O 9 , i.e. Mg 4 Ta 2 O 9-x N y , shows promising photocatalytic activities for water reduction and oxidation under visible light illumination (λ ≥ 400 nm). Apparent quantum efficiency as high as ∼1.57% has been achieved at 420 ± 20 nm which is comparable to a number of active metal oxynitride photocatalysts. Photoelectrochemical analysis suggests that this band gap reduction stems mainly from an uplift of valence band edge position along with nitrogen doping. Our band gap engineering on a compact corundum type compound implies that nitrogen doping can be applicable to a wider range of metal oxides, not necessarily limited to those with an 'open' crystal structure (tunnels or layers, etc.) reported in the literatures, thereby opening new possibilities in searching and developing visible light active photocatalysts. [ABSTRACT FROM AUTHOR]

Ultrathin titanoniobate nanosheet co-doped with Cr/Nb have been fabricated which show superior photocatalytic activity for H 2 production from water under both full range (λ ≥ 250 nm) and visible light illumination (λ ≥ 400 nm). • Titanoniobate nanosheets with thickness of a few nanometers have been prepared. • Cr/Nb co-dopants can be introduced into these nanosheets. • Cr/Nb modified nanosheets own a large surface area and visible light sensitivity. • Nanosheets show superior photocatalytic activity for H 2 production. • Dopants Cr at the surface may serve as catalytic reactive sites. Titanoniobate nanosheets with thickness down to a few nanometers have been prepared by ion exchange and subsequent exfoliation treatment on a bulk layer compound KTiNbO 5. Superior photocatalytic H 2 production activity has been realized on these nanosheets, surpassing their mother compound KTiNbO 5. More interestingly, their photocatalytic activity has been successfully extended into visible light region when Cr/Nb co-dopants are introduced into nanosheets. The Cr/Nb modified nanosheets show apparent quantum efficiency as high as 2.75% at 420 ± 20 nm for H 2 production, outperforming a number of doped metal oxides photocatalysts. Such high photocatalytic activity origins from their tiny thickness and a much enlarged surface area that favors charge separation and transfer. Their little dependence on cocatalyst for H 2 production suggest that dopants Cr may also serve as catalytic reaction sites as a substantial fraction of Cr dopants are accommodated at the surface. This facile approach to fabricate ultrathin 2D semiconductor as well as versatility of doping strategy open new playground for the design and development of efficient visible light active photocatalysts. [ABSTRACT FROM AUTHOR]

We have identified a facet-assisted mechanism for photocarrier separation in flux-treated Bi 4 TaO 8 Cl crystals that expose mainly {001} and {110} facets. These two crystal facets have different energy states that provide an internal electric field to split photocarriers towards different crystal facets. We have further leveraged the phenomenon by facet-selective deposition of CoO x cocatalyst at {001} crystal facets where holes are accumulated to expedite interfacial charge transfer reactions. The coupling of these two facet-engineering techniques brings exquisite control over the flow of photocarriers which cascade continuously from bulk to the surface for catalytic reactions. Under optimal conditions, the CoO x -deposited Bi 4 TaO 8 Cl achieves an unprecedentedly high apparent quantum efficiency of 27% at 420 ± 20 nm for water oxidation into O 2. Stable overall water splitting into H 2 and O 2 (molar ratio 2:1) under visible light irradiation has also been realized in a Z-scheme system employing the CoO x -deposited Bi 4 TaO 8 Cl as the O 2 -evolution moiety. [Display omitted] • Facet-assisted charge separation is identified for fluxed Bi 4 TaO 8 Cl crystals. • The diverse energy states of {001} and {110} facets result in an internal electric field. • Facet-selective cocatalyst deposition further upgrades photocarrier utilization. • An AQE of 27% at 420 ± 20 nm is reached for photocatalytic O 2 -evolution. • Stable Z-scheme overall water splitting is attained using fluxed Bi 4 TaO 8 Cl crystals. [ABSTRACT FROM AUTHOR]

The separation of photocarriers (e- and h+) is of critical importance in initiating efficient catalytic reactions over semiconductor-based photocatalysts. Although heterostructures have been frequently built to separate photocarriers, the lack of proper heterogeneous interfaces greatly limits their efficacies. Here, we show that excellent heterogeneous interfaces can be built for in situ fabricated Ta 3 N 5 @CaTaO 2 N heterostructures. These interfaces are characterized by perfectly matching (020) crystal facets of Ta 3 N 5 and CaTaO 2 N, offering ideal channels for charge transportation. As revealed by both experimental and theoretical analysis, these seamless interfaces enable rapid spatial photocarrier separation, which in turn, contribute to exceptional photocatalytic activity. Under optimal conditions, Ta 3 N 5 @CaTaO 2 N heterostructures achieve apparent quantum efficiency as high as 14.52% at 420 ± 20 nm for O 2 -evolution, substantially surpassing Ta 3 N 5 , CaTaO 2 N, and their mixtures. These results not only justify the importance of heterogeneous interfaces for photocarrier separation but also invigorate more attention upon heterostructures towards efficient solar water splitting. [Display omitted] • Ta 3 N 5 @CaTaO 2 N heterostructures have seamless interfaces due to crystal facet matching. • The seamless interfaces enable fast spatial photocarrier separation. • Ta 3 N 5 @CaTaO 2 N heterostructures show exceptional photocatalytic water oxidation into O 2. • An AQE of 14.52% at 420 ± 20 nm has been reached for O 2 -evolution. • The seamless heterogeneous interfaces can be the key to open up the photocatalytic potential. [ABSTRACT FROM AUTHOR]

Porous single-crystalline SrTaO 2 N, combining structural homogeneity and high porosity, afford a great promise as an active photocatalyst. The lack of grain boundaries in SrTaO 2 N porous single crystals (PSCs) enables fast photocarrier migration from bulk to the surface whilst the high porosity offers adequate accessible surface to perform photocatalytic reactions. In this work, we demonstrate a facile synthesis of SrTaO 2 N PSCs via a topotactic conversion route. These SrTaO 2 N PSCs deliver exceptional activity and stability for photocatalytic O 2 production from water with a record-breaking apparent quantum efficiency as high as 17.9% at 420 ± 20 nm. Overall water splitting with H 2 /O 2 equals 2 has also been attained in a Z-scheme system employing SrTaO 2 N PSCs as the O 2 -evolution moiety. These results signify a paradigm to improve photocatalytic performance based on PSCs, which extends the toolbox to achieve efficient solar water splitting over conventional photocatalysts. SrTaO 2 N porous single crystals, combining structural homogeneity and high porosity, deliver exceptional performance for photocatalytic water splitting reactions. The absence of grain boundaries enables fast photocarriers' transportation from bulk to the surface thereby facilitates photocarrier separation. The high porosity provides ample reachable surface to hold photochemical reactions as well as to shorten the transportation distance for photocarriers. [Display omitted] • SrTaO 2 N porous single crystals (PSCs) have been prepared by a topotactic route. • SrTaO 2 N PSCs own superior photocarrier transportation and separation conditions. • SrTaO 2 N PSCs deliver exceptional photocatalytic performance for water oxidation. • Apparent quantum efficiency as high as 17.9% at 420 ± 20 nm has been reached. • Overall water splitting is realized in a Z-scheme system containing SrTaO 2 N PSCs. [ABSTRACT FROM AUTHOR]