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Amino acids are the building blocks of proteins and are widely used as important ingredients for other nitrogen‐containing molecules. Here, we report the sustainable production of amino acids from biomass‐derived hydroxy acids with high activity under visible‐light irradiation and mild conditions, using atomic ruthenium‐promoted cadmium sulfide (Ru1/CdS). On a metal basis, the optimized Ru1/CdS exhibits a maximal alanine formation rate of 26.0 molAla ⋅ gRu−1 ⋅ h−1, which is 1.7 times and more than two orders of magnitude higher than that of its nanoparticle counterpart and the conventional thermocatalytic process, respectively. Integrated spectroscopic analysis and density functional theory calculations attribute the high performance of Ru1/CdS to the facilitated charge separation and O−H bond dissociation of the α‐hydroxy group, here of lactic acid. The operando nuclear magnetic resonance further infers a unique "double activation" mechanism of both the CH−OH and CH3−CH−OH structures in lactic acid, which significantly accelerates its photocatalytic amination toward alanine. [ABSTRACT FROM AUTHOR]

The optimal ratio of reaction solutions resulted in excellent performance and product selectivity of CuO/g-C3N4 composites in the photocatalytic CO2 reduction reaction. A pH-dependent chemical exchange saturation transfer (CEST) imaging nuclear magnetic resonance (NMR) method was used to confirm that CuO modification improves the adsorption capacity of CO2. [ABSTRACT FROM AUTHOR]

The photocatalytic production of hydrogen via single-atom catalysts (SACs), in which photoactive metal species are isolated as single atoms on supports, has received increasing interest for the ecologically friendly and sustainable production of hydrogen due to the high catalytic activity, selectivity, stability, and complete utilization of active components in these catalysts. However, a truly facile means of fabricating SACs without the aggregation of the active atoms remains poorly developed. The present work addresses this issue by proposing the use of a novel photochemical reaction conducted in a frozen precursor solution to prepare SACs with active Pd atoms stabilized on graphene carbon nitride (g-C3N4) supports. The single Pd atoms are demonstrated to be fully isolated on the g-C3N4 supports, and the optimal Pd–C3N4 SAC with 0.3 wt% Pd (the ICP result is 0.2855 wt%) is shown to provide a much higher photocatalytic hydrogen production performance (8.736 mmol g−1 h−1) than the non-frozen control group fabricated with an equivalent liquid precursor. Furthermore, computational methods are applied to explain how the proposed photochemical process stabilizes single-atom active sites and the chemical mechanisms responsible for the excellent photocatalytic hydrogen production performance of the SAC. These results demonstrate that the proposed fabrication method can be universally applied for the preparation of SACs. [ABSTRACT FROM AUTHOR]

Nonradiative recombination at perovskite/charge transport layer interfaces is caused by surface defects and instability, and it is known to limit the long-term development of perovskite solar cells (PSCs). To overcome this issue, the three-dimensional/two-dimensional (3D/2D) perovskite heterojunction has emerged as a possible solution to improve the stabilities and efficiency of PSCs. Herein, we employ a simple one-step method to prepare n-i-p-structured PSCs using a 3D/2D perovskite heterojunction as the absorption layer. For this purpose, the large and non-centrosymmetric 4,4-difluorocyclohexylammonium (DFCHA+) cation, which has been confirmed to be a valid organic spacer in 2D Ruddlesden–Popper (RP) phase perovskites, is employed as an organic ligand for post-treatment of the surfaces of MAPbI3 films. The presence of an ultrathin 2D RP phase perovskite was confirmed on the surface, and the 3D/2D perovskite heterojunction was successfully constructed. Benefitting from surface post-treatment, the density of the surface trap states was reduced with effective passivation. In addition, nonradiative recombination was suppressed, and the interface bands were aligned. As a result, the optimal device achieved a power conversion efficiency of 21.93% with a remarkable open-circuit voltage (VOC) of 1.14 V, a current density (JSC) of 23.71 mA cm−2, and a fill factor of 0.82. Furthermore, owing to the hydrophobicity of the DFCHA+ cation, the unencapsulated device was able to maintain an initial efficiency of 82.3% after storage for 500 h at a relative humidity of ∼45%. We believe that this post-treatment strategy has wide application potential in the field of photovoltaic devices. [ABSTRACT FROM AUTHOR]

Solar‐driven transfer hydrogenation of unsaturated bonds has received considerable attention in the research area of sustainable organic synthesis; however, water, the ultimate green source of hydrogen, has rarely been investigated due to the high barrier associated with splitting of water molecules. We report a carbon‐nitride‐supported palladium single‐atom heterogeneous catalyst with unparalleled performance in photocatalytic water‐donating transfer hydrogenation compared to its nanoparticle counterparts. Isotopic‐labeling experiments and operando nuclear magnetic resonance measurements confirm the direct hydrogenation mechanism using in situ‐generated protons from water splitting under visible‐light irradiation. Density functional theory calculations attribute the high activity to lower barriers for hydrogenation, facilitated desorption of ethylbenzene, and facile hydrogen replenishment from water on the atomic palladium sites. [ABSTRACT FROM AUTHOR]

Copper‐based materials are efficient electrocatalysts for the conversion of CO2 to C2+ products, and most these materials are reconstructed in situ to regenerate active species. It is a challenge to precisely design precatalysts to obtain active sites for the CO2 reduction reaction (CO2RR). Herein, we develop a strategy based on local sulfur doping of a Cu‐based metal–organic framework precatalyst, in which the stable Cu−S motif is dispersed in the framework of HKUST‐1 (S‐HKUST‐1). The precatalyst exhibits a high ethylene selectivity in an H‐type cell with a maximum faradaic efficiency (FE) of 60.0 %, and delivers a current density of 400 mA cm−2 with an ethylene FE up to 57.2 % in a flow cell. Operando X‐ray absorption results demonstrate that Cuδ+ species stabilized by the Cu−S motif exist in S‐HKUST‐1 during CO2RR. Density functional theory calculations indicate the partially oxidized Cuδ+ at the Cu/CuxSy interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimized adsorption energy. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) has been identified as a promising material for photocatalytic hydrogen (H2) production, but it shows a low activity. Herein, g-C3N4 doped with a benzene ring (B–CNx) was synthesized via a simple thermal polycondensation method, exhibits 5.4 times higher H2 evolution rate than the pristine one, and achieves a high apparent quantum yield of 4.11% at 420 nm. [ABSTRACT FROM AUTHOR]

The relationship between the structural characteristics and photocatalytic reaction mechanisms of graphitic carbon nitride (g-C3N4) still remains unclarified at the molecular level, which severely hinders the further development of this field. The present study addresses this issue by employing an innovative strategy to investigate the relationship between the H-containing structures of g-C3N4 and its water splitting properties. The exchangeable and unexchangeable protons of the H-containing groups of g-C3N4 were differentiated by selective deuteration, providing a way to distinguish the hydrophilic and relatively non-hydrophilic H-containing groups of g-C3N4. A combination of advanced solid-state NMR approaches reveals that amino group defects (CN2(NHx)) on the C–N skeleton of the photocatalyst likely serve as hydrophilic active sites for facilitating the photocatalytic hydrogen evolution reaction. Accordingly, the newly synthesized g-C3N4 sample having a high concentration of CN2(NHx) by design demonstrates an enhanced H2 yield by a factor of 17 compared to that of pure g-C3N4. [ABSTRACT FROM AUTHOR]

Chlorine incorporation engineering has been widely used in optoelectronic devices based on methylammonium lead iodide (MAPbI3) perovskites. However, the characteristics of I/Cl alloying structures in MAPbI3−xClx mixed-halide perovskites and their influences on the optoelectronic properties have been issues of a long-standing controversy. Here, we present a detailed study of the I/Cl alloying structures in MAPbI3−xClx (x = 0.0 to 0.3) single crystals. We found that a small amount of Cl can substitute for the iodide of the PbI3 inorganic lattice, leading to a phase transition from the tetragonal to cubic phase and anomalous cation dynamics evolution. Analyses based on time-dependent X-ray diffraction, 207Pb NMR, and 2H NMR indicate that the alloying structures of the MAPbI3−xClx crystals are metastable and decompose over time. In addition, the photocurrent response measurement of MAPbI3−xClx proved a close correlation between the alloying structures and photoelectric properties of the material. This work sheds light on the essential understanding of the I/Cl alloying structure and provides a plausible explanation for the controversy regarding the role of chloride ions in optoelectronic devices. Optoelectronic materials: Tracking changes at the atomic level A more complete understanding of alloy formation in an exciting class of optoelectronic materials has been developed by researchers in China, which could help improve solar-cell efficiency. Lead halide perovskites are used in low-cost, lightweight and flexible electronic devices. The properties of the perovskite can be modified to suit a specific application by doping, exchanging some atoms in the crystal for others, but this can make the structure unstable. Xue Lu Wang, Ye-Feng Yao and colleagues from the East China Normal University, Shanghai, tracked atomic structure changes in perovskite methylammonium lead iodide as the iodine atoms were partially replaced by chlorine atoms. The team showed that the state of chloride in MAPbI3−xClx crystals is metastable and the crystal lattice can transform from a cubic to a tetragonal structure over time. The characteristics of I/Cl alloying structures in MAPbI3-xClx mixed-halide perovskites and their influences on the optoelectronic properties have been issues of long-standing controversy. In this work, by using on the time-dependent X-ray diffraction, 207Pb and 2H NMR, the authors investigated the I/Cl alloying structures and its long term stability in MAPbI3-xClx (x = 0.0 to 0.3) single crystals. It was found that Cl can substitute for I of the PbI3 inorganic lattice, leading to the tetragonal to cubic phase transition. Moreover, it revealed that the alloying structures of the MAPbI3-xClx crystals are metastable and may decompose over time. [ABSTRACT FROM AUTHOR]

Metallic Ni3P/Ni can be used as a co-catalyst to replace noble metal Pt for efficient photocatalytic hydrogen evolution, due to its excellent trapping-electron ability. The applications of metallic Ni3P/Ni co-catalyst on CdS, Zn0.5Cd0.5S, TiO2 (Degussa P25) and g-C3N4 are further confirmed, indicating its versatile applicability nature like Pt. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) is a promising two-dimensional polymeric photocatalyst in the field of solar energy conversion. In the past few years many modifications of g-C3N4 have been studied extensively; however, the difficulty in obtaining detailed structural information both on its intrinsic covalent interactions and surrounding bonding environments largely restricts the rational design and development of inherent structure-controlled g-C3N4 based photocatalysts and fundamental understanding of their mechanistic operations. Herein, we demonstrate a high-pressure hydrogenation treatment method for g-C3N4 and introduce 1D 13C and 15N and 2D 15N Radio Frequency-driven Dipolar Recoupling (RFDR) solid-state nuclear magnetic resonance spectroscopy for identifying the structural information and surrounding hydrogen-bonding environment of treated g-C3N4 samples. The surface Brønsted base sites of g-C3N4 samples can be tuned systematically through changing the treatment conditions. We find that the terminal isolated –NH2 and the hydrogenated nitrogen species in treated g-C3N4 samples seem to be the origin of their improved activities for photocatalytic hydrogen evolution and favor the enhancement of light harvesting and carrier transport. The as-prepared HCN400-4-2 sample treated at a pressure of 4 MPa and a temperature of 400 °C for 2 h in a hydrogen atmosphere displays the highest H2 evolution reaction (HER) activity, which is over 26 times higher than that of pristine g-C3N4. [ABSTRACT FROM AUTHOR]

The atomically controlled transition of nanohybrids and their effects on charge-carrier dynamics are highly desirable for fundamental studies in photocatalysis. Herein, for the first time, a method combining atomic monodispersity and single-atom alloy was used to prepare a new form of highly efficient silver-based cocatalysts (Ag25 & Pt1Ag24) on graphitic carbon nitride, representing a novel photocatalytic system for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization. [ABSTRACT FROM AUTHOR]

Facilitating charge-carrier separation and transfer is fundamentally important to improve the photocatalytic performance of semiconductor materials. Herein, two-dimensional hexagonal WO3 nanoplates were synthesized by a two-step route: rapid evaporation and solid-phase sintering. The as-prepared WO3 exhibits an enhanced activity of photocatalytic water oxidation compared to bulk monoclinic WO3. The electron dynamics analysis reveals that a more efficient charge-carrier separation in the former can be obtained, the origin of which can be attributed to an increased number of surface defects in hexagonal WO3 nanoplates. This work not only presents a novel and simple method to produce two-dimensional hexagonal WO3 nanoplates, but also demonstrates that surface defects and two-dimensional geometric structures can promote the charge separation, which may be extended to the design of other efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Doping has been widely used to engineer efficient photocatalysts for the water-splitting process in energy conversion and storage systems. Although composition tuning through heteroatom doping is one of the strategies to enhance photoactivity, the origin of the increased activity by doping remains unclear and most illustrations of its role fall in the band engineering area. Herein, it is reported that the rhodium dopants on the surface of Zn2GeO4, which affect the band structure negligibly, can act as active sites for water splitting. As a result, the Rhδ+/Zn2GeO4 photocatalyst demonstrates excellent stability for up to 460 days and significant enhancement of the photocatalytic activity to that of the undoped photocatalyst. The findings in this work may open the door for a rethink of the detailed principles of dopants in photocatalysis, and highlight a feasible route to fabricating efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Porous oxygen-doped graphitic carbon nitride (g-C3N4) with feeble nitrogen vacancies was fabricated through thermal polycondensation of melamine with an appropriate amount of polyvinylpyrrolidone. After optimization, the bandgap of g-C3N4 can be narrowed by 0.2 eV and the specific surface area expanded, which contribute to increasing the utilization of solar energy. Consequently, the optimized g-C3N4 exhibits impressive enhancement in photocatalytic hydrogen evolution performance, by nearly 5 times compared with the pristine one under the irradiation of visible light. [ABSTRACT FROM AUTHOR]

Fluorine-doped hierarchical porous single-crystal rutile TiO2 nanorods have been synthesized through a silica template method, in which F− ions acts as both n-type dopants and capping agents to make the isotropic growth of the nanorods. The combination of high crystallinity, abundant surface reactive sites, large porosity, and improved electronic conductivity leads to an excellent photoelectrochemical activity. The photoanode made of F-doped porous single crystals displays a remarkably enhanced solar-to-hydrogen conversion efficiency (≈0.35 % at −0.33 V vs. Ag/AgCl) under 100 mW cm−2 of AM=1.5 solar simulator illumination that is ten times of the pristine solid TiO2 single crystals. [ABSTRACT FROM AUTHOR]

In this work, we report a facile and nontoxic one-pot hydrothermal method for synthesizing F-doped rutile single crystalline TiO2 with tuneable solar absorption. The optical band gap of the catalyst can be easily manipulated from 3.05 to 2.58 eV via altering the initial F : Ti molar ratio of reaction precursors. The photoanodes made of rutile TiO2 single crystals with appropriate F-doping concentration show excellent photoelectrocatalytic activity towards water oxidation under ultraviolet and visible light illumination. The best photoelectrocatalytic performance under UV irradiation can be obtained by F-doped TiO2 with an initial F : Ti molar ratio of 0.1, which is almost 15 times higher than that of un-doped TiO2. Further, the F-doped TiO2 photoanodes also exhibit superior photoelectrocatalytic activity under visible irradiation, and the best performance can be achieved by F-doped TiO2 photoanode with an initial F : Ti molar ratio of 0.05. The superior photoelectrocatalytic activity could be attributed to the highly n-type dopant introduced by fluorine, which significantly tunes the electrical conductivities and band structures of the resulting TiO2 photoanodes, and thus the photoelectrocatalytic activities under both UV and visible irradiation. Different techniques have been employed to characterize the electrical conductivity, charge carrier density and band structures of the F-doped rutile TiO2 films, such as photoelectrochemical method, electrical impedance spectroscopy (EIS) measurements, Mott–Schottky plots and XPS valence band spectra. [ABSTRACT FROM AUTHOR]

Hydrogen bonding (H-bond) interactions have been regarded as a topic of vital scientific research in areas ranging from inorganic to biological chemistry. However, the application and elucidation of surface H-bond functionalized photocatalysts and the alteration of the character of the photocatalyst itself have not been paid sufficient attention. Here we show the high efficiency of visible-light-driven photocatalytic H2 production, achieved by using a surface H-bonding network decorated g-C3N4 photocatalyst. The hydrated g-C3N4 was designed and synthesized by a facile surface treatment in a slightly alkaline environment. According to NMR and theoretical modeling, the H-bonding bridge can effectively shorten the distance between water molecules and g-C3N4, provide multiple channels for the transition between protons and the excited electrons on g-C3N4, stabilize the anionic intermediate and transition states, and restrain charge recombination. The present result opens new opportunities towards a potential approach to designing a new generation of photocatalyst systems. [ABSTRACT FROM AUTHOR]

The development of novel, noble metal-free semiconductor catalysts with high efficiency is of great importance for the degradation of organic compounds. Among them, amorphous materials have been extensively studied for their unique and commercially useful properties. Here, a completely amorphous, noble metal-free photocatalyst C3N4ZnxOy (x, y = 0.32–1.10) was successfully synthesized from urea and ZnO by a simple high-temperature polymerization method. As the Zn content increased, the short-range ordered structures of the amorphous samples were still retained, as revealed by XPS, FTIR, and ssNMR. Meanwhile, the -CN3 structures were observed to be gradually destroyed, which may make the amorphous state more favorable for photocatalytic reactions. Compared with g-C3N4, the amorphous samples showed significantly reduced intensities in the photoluminescence spectra, indicating that the recombination rate of the photo-generated charge carriers was greatly reduced. It was confirmed that the optimized sample (C3N4Zn0.61O0.61) achieved a photocatalytic efficiency of 86.1% in the degradation of tetracycline hydrochloride under visible light irradiation within 1 h. This is about 2 times higher than that of both g-C3N4 and ZnO. This study emphasizes the importance of the amorphous structure in photocatalytic reactions, and this synthetic strategy may provide an effective model for designing other novel catalysts. [ABSTRACT FROM AUTHOR]

Engineering surface-active facets of metal cocatalysts is one of the most widely explored strategies to develop advanced photocatalysts and promote photocatalytic solar energy conversion. Here, the surface-active facets of Pd nanocrystals in Pd/g-C 3 N 4 photocatalyst was related to the injection flow rate of PdCl 2. When PdCl 2 was injected at a low flow rate of 7.5 mL/h (7.5-Pd/g-C 3 N 4), the Pd nanocrystals were uniformly dispersed onto the g-C 3 N 4 with exposed low-index {100} and {111} surface-active facets. However, increasing the injection flow rate to 150 mL/h (150-Pd/g-C 3 N 4) formed Pd nanocrystals where only the {100} surface-active facet was exposed. Under visible light irradiation, the 7.5-Pd/g-C 3 N 4 nanocomposite exhibited excellent water splitting activity for hydrogen production (7.61 mmol g−1 h−1), which was significantly better than with the 150-Pd/g-C 3 N 4 nanocomposite (3.3 mmol g−1 h−1). Theoretical calculations and experimental results confirm the importance of the {111} surface-active facets in the 7.5-Pd/g-C 3 N 4 nanocomposite for promoting photocatalytic activity. [Display omitted] • The Pd/g-C 3 N 4 photocatalyst was prepared in a simple one-pot synthesis method. • The surface-active facets of Pd nanocrystals in Pd/g-C 3 N 4 was controlled by the injection flow rate of PdCl 2. • 7.5-Pd/g-C 3 N 4 nanocomposite exhibited excellent photocatalytic activity for H 2 production. • 7.5-Pd/g-C 3 N 4 nanocomposite also shown good performance in varied photocatalytic reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Operando NMR combined with gas-probe method was used to study active sites transfer under the metal-support interaction. • The photocatalytic conversion efficiency of pure TiO 2 decreased, while that of Pt/TiO 2 was unaffected in gas conditions. • After loading metal-Pt, active sites changed from TiO 2 surface to Pt/TiO 2 interface. Recently metal-support interaction (MSI) has attracted considerable attention in photocatalysis. Some studies emphasize the importance of active sites on photocatalysts; however, there are no reports on site changes under MSI in real reactive conditions. Herein, an operando nuclear magnetic resonance technique was proposed to study such site changes on anatase TiO 2 and Pt/TiO 2 , through a gas-probe method, in CH 3 OH reforming. The photocatalytic oxidation efficiency of CH 3 OH by pure TiO 2 decreased immensely under extra-gas conditions, while that by Pt/TiO 2 was unaffected. The surface of pure TiO 2 were occupied by injected gas molecules, making CH 3 OH inaccessible to active sites. However, in Pt/TiO 2 , CH 3 OH adsorption sites changed from TiO 2 surface to metal-Pt/TiO 2 interface as confirmed by H 2 gas-probe experiments. This study provides a deeper understanding of active sites transfer by MSI and leverages the gas-probe method for its detection to guide the development of technology to test active-site positions in heterogeneous catalysts. [ABSTRACT FROM AUTHOR]