Multifunctional Nitrogen‐Doped Carbon Nanodots for Photoluminescence,Sensor, and Visible‐Light‐Induced H2 Production

Herein, multifunctional N‐doped carbon nanodots (NCNDs) were prepared through the one‐step hydrothermal treatment of yeast. Results show that the NCNDs can be used as a new photocatalyst to drive the water‐splitting reaction under UV light. Moreover, the NCNDs can efficiently catalyze the hydrogen evolution reaction. Under visible‐light irradiation, Eosin Y‐sensitized NCNDs exhibit excellent activity for hydrogen evolution. The hydrogen evolution rate of NCNDs (without any modification and co‐catalyst) reaches 107.1 μmol h^?1 (2142 μmol g^?1 h^?1). When Pt is loaded on the NCNDs, the hydrogen evolution rate reaches 491.2 μmol h^?1 (9824 μmol g^?1 h^?1) under visible‐light irradiation. In addition, the NCNDs show excellent fluorescent properties and can be applied as a fluorescent probe for the sensitive and selective detection of Fe³⁺.     

Consecutive Charging of a Perylene Bisimide Dye by Multistep Low‐Energy Solar‐Light‐Induced Electron Transfer Towards H2 Evolution

A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO₂) nanoparticles through carboxyl groups was constructed. Under solar‐light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI^.?), which in a second step absorbs near‐infrared light, forming a stable PBI dianion (PBI^2?). Finally, the dianion absorbs red light and injects an electron into the TiO₂ nanoparticle that is coated with platinum co‐catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 μmol h^?1 g^?1 with simulated sunlight irradiation in neutral and basic conditions, respectively.     

Enhanced photocatalytic hydrogen production under visible light of an organic-inorganic hybrid material based on enzo[1,2-b:4,5-b']dithiophene polymer and TiO2

Titanium dioxide (TiO₂) has been limited in photocatalysis due to its wide band gap (3.2 eV) and limited absorption in the ultraviolet range. Therefore, organic components have been introduced to hybrid with TiO₂ for enhanced photocatalytic efficiency under visible light. Here, we report that benzo[1,2-b:4,5-b']dithiophene polymer was an ideal organic material for the preparation of a hybrid material with TiO₂. The energy band gap of the resulting hybrid material decreased to 2.9 eV and the photocatalytic hydrogen production performance reached 745.0 µmol g^?1 h^?1 under visible light irradiation. Meanwhile, the material still maintained the stability of hydrogen production performance after 40 h of photocatalytic cycles. The analysis of the transient current response and electrochemical impedance revealed that the main reasons for the enhanced water splitting of the hybrid materials were the faster separation of electron hole pairs and the lower recombination of photocarrier ions. Our findings suggest that polythiophene is a promising organic material for exploring hybrid materials with enhanced photocatalytic hydrogen production.     

Palladium Single Atoms on TiO2 as a Photocatalytic Sensing Platform for Analyzing the Organophosphorus Pesticide Chlorpyrifos

Traditional methods for analyzing organophosphorus pesticide chlorpyrifos, usually require the tedious sample pretreatment and sophisticated bio‐interfaces, leading to the difficulty for real‐time analysis. Herein, we use palladium single‐atom (PdSA)/TiO₂ as a photocatalytic sensing platform to directly detect chlorpyrifos with high sensitivity and selectivity. PdSA/TiO₂, prepared by an in situ photocatalytic reduction of PdCl₄^2? on the TiO₂, shows much higher photocatalytic activity (10 mol g^?1 h^?1) for hydrogen evolution reaction than Pd nanoparticles (1.95 mol g^?1 h^?1), and excellent stability. In the presence of chlorpyrifos, the photocatalytic activity of PdSA/TiO₂ decreases. Through this inhibition effect the platform can realize a detection limit for chlorpyrifos of 0.01 ng mL^?1, much lower than the maximum residue limit (10 ppb) permitted by the U.S. Environmental Protection Agency.     

Strong‐Base‐Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF‐HUST‐A1 with a benzylamine‐functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF‐HUST‐A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g^?1 h^?1). Photocatalytic overall water splitting is achieved by depositing dual co‐catalysts in CTF‐HUST‐A1, with H₂ evolution and O₂ evolution rates of 25.4 μmol g^?1 h^?1 and 12.9 μmol g^?1 h^?1 in pure water without using sacrificial agent.     

Photothermal Conversion of CO2 into CH4 with H2 over Group VIII Nanocatalysts: An Alternative Approach for Solar Fuel Production

The photothermal conversion of CO₂ provides a straightforward and effective method for the highly efficient production of solar fuels with high solar‐light utilization efficiency. This is due to several crucial features of the Group VIII nanocatalysts, including effective energy utilization over the whole range of the solar spectrum, excellent photothermal performance, and unique activation abilities. Photothermal CO₂ reaction rates (mol h^?1 g^?1) that are several orders of magnitude larger than those obtained with photocatalytic methods (μmol h^?1 g^?1) were thus achieved. It is proposed that the overall water‐based CO₂ conversion process can be achieved by combining light‐driven H₂ production from water and photothermal CO₂ conversion with H₂. More generally, this work suggests that traditional catalysts that are characterized by intense photoabsorption will find new applications in photo‐induced green‐chemistry processes.     

Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H2 Evolution

A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO₂) nanoparticles through carboxyl groups was constructed. Under solar-light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI^.−), which in a second step absorbs near-infrared light, forming a stable PBI dianion (PBI²⁻). Finally, the dianion absorbs red light and injects an electron into the TiO₂ nanoparticle that is coated with platinum co-catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 μmol h⁻¹ g⁻¹ with simulated sunlight irradiation in neutral and basic conditions, respectively.     

Enhanced photocatalytic hydrogen production performance of pillararene-doped mesoporous TiO2 with extended visible-light response

Pillararenes are a new type of supramolecular hosts,and they have been widely applied in drug delivery,catalysis,separation process,and sensors.However,they have rarely been used to produce hydrogen.Here,we report that pillararenes were used as functional molecules to explore photocatalysts and efficiently promoted hydrogen production from water.The most common and easily synthesized pdimethoxy pillar[5]arene（PI-OMe） was employed to form an organic-inorganic hybrid material with titanium dioxide...     

A Hydrogen‐Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low‐cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble‐metal co‐catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so‐called L‐NiCo nanosheets with a nonstoichiometric composition and O^2?/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O^2? and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h^?1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

An Elemental Phosphorus Photocatalyst with a Record High Hydrogen Evolution Efficiency

Semiconductive property of elementary substance is an interesting and attractive phenomenon. We obtain a breakthrough that fibrous phase red phosphorus, a recent discovered modification of red phosphorus by Ruck et al., can work as a semiconductor photocatalyst for visible‐light‐driven hydrogen (H₂) evolution. Small sized fibrous phosphorus is obtained by 1) loading it on photoinactive SiO₂ fibers or by 2) smashing it ultrasonically. They display the steady hydrogen evolution rates of 633 μmol h^?1 g^?1 and 684 μmol h^?1 g^?1, respectively. These values are much higher than previous amorphous P (0.6 μmol h^?1 g^?1) and Hittorf P (1.6 μmol h^?1 g^?1). Moreover, they are the highest records in the family of elemental photocatalysts to date. This discovery is helpful for further understanding the semiconductive property of elementary substance. It is also favorable for the development of elemental photocatalysts.     

Hydrothermal Preparation and Characterization of TiO2/BiVO4 Composite Catalyst and its Photolysis of Water to Produce Hydrogen

In the present work, bismuth vanadate composited photocatalysts were synthesized and characterized. X‐ray diffractometry and Raman results showed that the particles were well crystallized, and formed by the complex of monoclinic BiVO₄ and TiO₂. On electron microscopy, the photocatalyst exhibited high crystallization, agglutination and irregular shape, and was surrounded by numerous TiO₂ particles. The study of surface areas showed that the specific surface area of 30‐BiVO₄/TiO₂ composited was 112 m²·g^?1, which was nearly 10 times that of pure BiVO₄. The ultraviolet–visible diffuse reflectance spectra indicated the composited photocatalyst were activated in visible light. The activity of photocatalytic water splitting was studied. The results showed that monomer BiVO₄ photocatalyst was not able to produce hydrogen under any light source. BiVO₄/TiO₂ composited photocatalysts, however, were capable of generating hydrogen. Under UV light irradiation for 120 min, 1 g catalyst dispersed in 50 mL deionized water produced almost 1 mL hydrogen, such that the productivity of hydrogen was higher than that of P25‐TiO₂. Photocatalytic decomposition of water under visible light also confirmed that the BiVO₄/TiO₂ composited photocatalyst had the ability of water splitting.     

Constructing SrTiO3–TiO2 Heterogeneous Hollow Multi‐shelled Structures for Enhanced Solar Water Splitting

Constructing hollow multi‐shelled structures (HoMSs) has a significant effect on promoting light absorption property of catalysts and enhancing their performance in solar energy conversion applications. A facile hydrothermal method is used to design the SrTiO₃?TiO₂ heterogeneous HoMSs by hydrothermal crystallization of SrTiO₃ on the surface of the TiO₂ HoMSs, which will realize a full coverage of SrTiO₃ on the TiO₂ surface and construct the SrTiO₃/TiO₂ junctions. The broccoli‐like SrTiO₃?TiO₂ heterogeneous HoMSs exhibited a fourfold higher overall water splitting performance of 10.6 μmol h^?1 for H₂ production and 5.1 μmol h^?1 for O₂ evolution than that of SrTiO₃ nanoparticles and the apparent quantum efficiency (AQE) of 8.6 % at 365 nm, which can be mainly attributed to 1) HoMS increased the light absorption ability of the constructed photocatalysts and 2) the SrTiO₃?TiO₂ junctions boosted the separation efficiency of the photogenerated charge carriers.     

Z‐Scheme Photocatalytic Water Splitting on a 2D Heterostructure of Black Phosphorus/Bismuth Vanadate Using Visible Light

Spontaneously solar‐driven water splitting to produce H₂ and O₂, that is, the conversion of solar energy to chemical energy is a dream of mankind. However, it is difficult to make overall water splitting feasible without using any sacrificial agents and external bias. Drawing inspiration from nature, a new artificial Z‐scheme photocatalytic system has been designed herein based on the two‐dimensional (2D) heterostructure of black phosphorus (BP)/bismuth vanadate (BiVO₄). An effective charge separation makes possible the reduction and oxidation of water on BP and BiVO₄, respectively. The optimum H₂ and O₂ production rates on BP/BiVO₄ were approximately 160 and 102 μmol g^?1 h^?1 under irradiation of light with a wavelength longer than 420 nm, without using any sacrificial agents or external bias.     

Nano‐Ferroelectric for High Efficiency Overall Water Splitting under Ultrasonic Vibration

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.     

Visible Light Photocatalytic Activity of Pt/N‐TiO2 towards Enhanced H2 Production from Water Splitting

Present work mainly focuses on experimental investigation to improvement of hydrogen production by water photoelectrolysis. An experimental facility was designed and constructed for visible light photocatalysis. A series of N‐TiO₂ photocatalysts impregnated with platinum on the surface of N‐TiO₂ were prepared. Hydrogen production upon irradiating aqueous Pt/N‐TiO₂ suspension with visible light was investigated. The shift in excitation wavelength of TiO₂ was 380 nm improved the yield of hydrogen production by N‐TiO₂ and Pt/N‐TiO₂. We used a 400 W mercury arc lamp combined with a 400 nm cutoff filter eliminating all the wavelengths under 400 nm. Pt/N‐TiO₂ material was characterized with TPR, reflective UV/Visible spectroscopy and TEM. The best hydrogen production rate obtained for this setup for N/Ti = 10, 0.05 wt% Pt/N‐TiO₂, through water splitting was about 772 μmolh^?1g^?1.     

Strong-Base-Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF-HUST-A1 with a benzylamine-functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF-HUST-A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g⁻¹ h⁻¹). Photocatalytic overall water splitting is achieved by depositing dual co-catalysts in CTF-HUST-A1, with H₂ evolution and O₂ evolution rates of 25.4 μmol g⁻¹ h⁻¹ and 12.9 μmol g⁻¹ h⁻¹ in pure water without using sacrificial agent.     

A novel P-doped and NCDs loaded g-C3N4 with enhanced charges separation for photocatalytic hydrogen evolution

Graphite carbon nitride(g-C₃N₄) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light.In this work, P-doped and N-doped carbon dots(NCDs) supported g-C₃N₄were successfully prepared via hydrothermal and polymerization reactions. The sub-bandgap formed by P-doping enhances the utilization of visible light, and the high electron de...     

Visible‐Light‐Induced Generation of H2 by Nanocomposites of Few‐Layer TiS2 and TaS2 with CdS Nanoparticles

Graphene analogues of TaS₂ and TiS₂ (3–4 layers), prepared by Li intercalation followed by exfoliation in water, were characterized. Nanocomposites of CdS with few‐layer TiS₂ and TaS₂ were employed for the visible‐light‐induced H₂ evolution reaction (HER). Benzyl alcohol was used as the sacrificial electron donor, which was oxidized to benzaldehyde during the reaction. Few‐layer TiS₂ is a semiconductor with a band gap of 0.7 eV, and its nanocomposite with CdS showed an activity of 1000 μmol h^?1 g^?1_. The nanocomposite of few‐layer TaS₂, in contrast, gave rise to higher activity of 2320 μmol h^?1 g^?1, which was attributed to the metallic nature of few‐layer TaS₂. The amount of hydrogen evolved after 20 and 16 h for the CdS/TiS₂ and CdS/TaS₂ nanocomposites was 14833 and 28132 μmol, respectively, with turnover frequencies of 0.24 and 0.57 h^?1, respectively.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1?xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g^?1 h^?1 and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

Highly Efficient Photocatalytic H2 Evolution from Water using Visible Light and Structure‐Controlled Graphitic Carbon Nitride

The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low‐cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g‐C₃N₄) from a low‐cost precursor, urea, is reported. The g‐C₃N₄ exhibits an extraordinary hydrogen‐evolution rate (ca. 20 000 μmol h^?1 g^?1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g‐C₃N₄ photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen‐evolution rate is significantly enhanced.