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The dehydrogenation and conversion of methanol into 1,1-dimethoxymethane (DMM) was achieved over noble metal-free photocatalyst CdS/Ni2P under visible light. This photocatalytic process for methanol-to-H2 and DMM conversion is efficient and atom economic, with an optimal rate and selectivity of DMM of 188.42 mmol g−1 h−1 and 82.93%, respectively. This work supplies a new green approach for the direct efficient conversion of methanol into DMM and provides a promising avenue for sustainable bio-methanol applications.

Designing cost-effective, highly efficient and stable electrocatalysts for oxygen evolution reaction is of paramount importance. Although extensive studies have focused on the relatively cheaper 3d transition metal oxide catalysts, the effect of trimetallic composites on the catalytic ability still remains elusive. Herein, we selected FeCo catalyst as the platform and investigated the catalytic activity of trimetallic composites, which were synthesized by incorporating Mo, W or Ni into the FeCo catalyst. The experimental results evidenced that FeCoMo/CP exhibited high catalytic activity towards water oxidation in alkaline solution, which required an overpotential of only ∼270 mV. Such impressive catalytic performance of FeCoMo/CP can be attributed to the fact that the introduction of Mo appreciably modulated the electronic structure of the Fe and Co centers, leading to an enhancement in intrinsic active sites. Benefiting from the tight contact with the highly conductive carbon paper substrate, FeCoMo/CP showed excellent stability up to 120 h. These results indicate that the surface engineering of FeCo-based catalysts by incorporating non-noble metals is a rational strategy to promote the performance of electrocatalysts.

Selective oxidation of alcohols to highly valued chemicals in a clean manner (e.g., with water as a solvent and O2 or H2O2 as the primary oxidant) is the subject of considerable research attention. This paper presents a simple and environmentally friendly approach for the selective oxidation of isopropanol to pinacol C6 (2,3-dimethyl-2,3-butanediol) in water with hydrogen peroxide (H2O2) through UV irradiation under mild conditions. A selectivity of 82–95% is achieved at H2O2 feeding rates below 4 mL h−1. The introduction of TiO2 nanotubes can further accelerate isopropanol conversion and enhance pinacol C6 formation. The highest formation rate of pinacol C6 and the highest conversion rate of isopropanol are 29.4 and 71.4 mmol h−1, respectively. The proposed strategy provides a green solution for the synthesis of aliphatic pinacol and offers a new design for the construction of C–C bonds with alphatic alcohol.

Water oxidation and reduction over semiconductor-based photocatalysts intrinsically occur at different spatial sites. Modulation of the reaction sites and charge transfer between them are logically important in speeding up the reaction. Here, we demonstrate that divorcing a CdSe–CdS–Pt donor–acceptor system on different surface sites of TiO2 can significantly increase the H2 generation rate. The increase is derived from an effective reset of water oxidation and reduction sites. Widening of the site distance by employing a TiO2 membraniform acceptor effectively decreases the electron–hole recombination especially for a membrane of TiO2 nanotube arrays. The oriented charge transfer characteristic of TiO2 nanotube arrays benefits long-range electron transport, thereby increasing the electron lifetime and reaction rate. When more conductive carbon nanotube arrays serve as an electron acceptor to replace TiO2, the electron transport is greatly improved, resulting in an ultrahigh H2 generation rate of 1270 mmol g−1 h−1. This work provides a basis for the design and construction of highly efficient photocatalysts through rational modulation of reaction sites and charge transport.

The morphological characteristics of a photocatalyst is central to its photocatalytic activity for solar energy conversion. Herein, Pt–ZnS/CdS composites comprising ZnS nanosheets, embedded via the geometry and size modulation and tuning of band gap of CdS with 0D, 1D or 2D structure, were investigated for solar hydrogen production. The photoactivity results indicate that the shape and morphology of CdS in the Pt–ZnS/CdS heterojunction play a pivotal role in affecting the photocatalytic performance. CdS with a 1D structure deposited on porous Pt–ZnS nanosheets endow the heterojunction with increased efficiency for the separation and transport of photoinduced electron–hole pairs. The proposed mechanism for the boosted suppression of charge recombination was further confirmed by the transient photocurrent response and photoluminescence.

The conversion of carbon dioxide into useful chemicals is a prospective strategy for alleviating the greenhouse effect and the depletion of energy. Herein, we report an artificial photosynthetic system composed of a photoanode and a photocathode comprised of NRx@TiO2 functionalized with Nile red via covalent linkage or Pd/NRx@TiO2 with additional palladium nanoparticles. The new Nile red derivatives and organic–inorganic composite electrodes were steadily prepared and well characterized using NMR, HRMS, UV-vis, FTIR, TEM, XPS, XRD and SEM. Methanol and oxygen were the products that could be detected in the liquid and gas phase. The main active species in this artificial photosynthesis system were proven using EPR spectroscopy to be hydroxy radicals releasing O2 gas via H2O2. Moreover, the carbon source of methanol was validated using a 13CO2 labeling experiment; 18O2 was determined to come from H2O using GC-MS. The optimal photoelectrocatalytic CO2 reduction was carried out using Pd/NR2@TiO2 as the working electrode yielding methanol at a rate of 106 μM h−1 cm−2 with high light quantum efficiency (Φcell = 0.95).

Facile carbon–carbon bond formation was achieved through the dehydrogenation coupling of acetone at the α-position. Using the H2O2/UV-light system, the acetonyl radicals that were formed from the selective cleavage of the α-C–H bond of acetone underwent a C–C coupling reaction. By modulating the instantaneous concentration of hydrogen peroxide, the direct C–C coupling of acetone was achieved. Moreover, the selectivity and generation rate of 2,5-hexanedione reached 67.4% and 8.6 mmol h−1, respectively.

To understand the mechanism of the photocatalytic direct synthesis of 1,1-diethoxyethane (DEE) from ethanol is vital for enhancing the reaction efficiency. Based on photocatalytic data of different phase TiO2 and F–TiO2 catalysts, radical trapping data, and GC-MS data, we proposed a photocatalytic mechanism for the preparation of both DEE in neat ethanol and 2,3-butanediol (2,3-BD) in ethanol–H2O using photocatalytic methods. In neat ethanol, hydroxyl isn’t involved in the catalytic cyclic process but hydroxyl has an indirect site-holding effect, thus leading to more hydroxyl groups with higher activity. In ethanol–H2O, although the strong oxidant ˙OH radical is involved, fewer OH groups lead to higher selectivity of 2,3-BD. The interaction of the reactant/solvent with the surface group of the catalyst is important in the activity and selectivity of photocatalytic reactions. This finding gives fundamental insight into the role of TiO2 surface hydroxyl in the photocatalytic dehydrogenation process of alcohols and opens a promising path to obtaining both high selectivity and high conversion in TiO2-based photocatalytic activity.

Tartronic acid (TA) is a high value-added chemical widely used as a pharmaceutical product and a preservative; however, its synthesis technology is complicated and high cost. In this study, aqueous solutions of lactic acid were photochemically converted into TA via green oxidation by using hydrogen peroxide (H2O2).

A new series of phenothiazine-based D–A–π–A dyes PZ-1–4 have been designed, synthesized and fully characterized by 1H, 13C NMR, HRMS, UV-vis, fluorescence, and cyclic voltammetry spectroscopy. Benzothiadiazole was introduced into the D–π–A dyes as an additional acceptor. Various donors and new π-spacers have been connected to phenothiazine skeleton on opposite sides to generate PZ-2–4 dyes. The DSSC devices have been systematically investigated by photoelectrochemical experiments, the solar cell of PZ-4 with a simple hexyloxyphenyl group achieves the highest photoelectric conversion efficiency of 6.35%. Density functional theory (DFT) calculation results demonstrate that the large dihedral angle (36.3°) between the π-spacer and phenothiazine in PZ-4 induces better charge separation. Its largest semicircle at intermediate frequencies in electrochemical impedance spectroscopy (EIS) prevents the recombination of photoelectrons injected into the titanium dioxide (TiO2) conductive band with I3− in electrolyte, which might be caused by the blocking interaction of the hexyloxy group dye.

Back reactions were suppressed effectively by double blocking barrier, organic molecules and ZnS on the photoanode of quantum dot (QDs) sensitized solar cells (QDSSCs), thereby achieving higher conversion efficiency. In this work, four different organic molecules were applied in QDSSCs, the efficiency increased two-fold from 2.21% to 4.25% when co-modifications with 4-tert-butyl pyridine (TBP) and ZnS were sequentially applied. The incident photon-to-current efficiency (IPCE) and parameters obtained from impedance spectroscopy (IS) such as recombination resistance (Rrec), chemical capacitance (Cμ), and electron lifetimes were consistent with the measured photovoltaic performance. We speculated that organic molecules mainly inhibit the charge recombination of the injected electrons in TiO2 with electrolyte, because of its steric factor and the electron-donating property of the tert-butyl group. The selective site of modification has been tested for assessing the dominant mechanism underlying the improvement of solar cell characteristics.

The hydrogenative cyclization of levulinic acid (LA) into γ-valerolactone (GVL) is an attractive route toward the use of renewable bio-sources but it normally suffers from the consumption of H2. In this study, we report that an intermolecular hydrogen transfer from isopropanol to LA can be realized efficiently under photocatalytic conditions over gold-loaded TiO2 catalysts. In this manner, isopropanol is dehydrogenated as acetone and pinacol with the total selectivity of >99%, whereas LA is hydrogenated and cyclized as GVL with the selectivity of up to 85%. In this reaction process, the production of GVL is mediated with hydrogenated dehydration of LA into an acetyl propionyl radical, which is further hydrogenated and cyclized as GVL. This hydrogenation–dehydrogenation coupling process provides an atom-economical green way for the conversion of LA into GVL.

Theoretically, selective C–H manipulation in ethanol can result in a direct C–C coupling synthesis of 2,3-butanediol (2,3-BDO). However, this process is typically extremely difficult to achieve because of the high complexity of the involved chemical bonds. In this work, we determine that hydroxide radicals generated from the photolysis of H2O2 can selectively attack the α-hydrogen atom in ethanol aqueous solutions and crack the C–H bond to produce hydroxyethyl radicals, which subsequently undergo C–C coupling to form 2,3-BDO. This selective C–H breakage is determined by the reaction rate, which is primarily controlled by the local H2O2 concentration at a given irradiation intensity. At a moderate reaction rate of ethanol (37 mmol h−1), the 2,3-BDO selectivity reaching as high as 91% can be obtained. The introduction of a catalyst can further increase ethanol conversion and enhance the 2,3-BDO formation rate by controlling the reaction rate. This result provides an environment-friendly approach to convert bio-ethanol directly to 2,3-BDO and to manipulate a single bond selectively in complex bonding situations.

Carbon nanodots without any modification can drive photocatalytic hydrogen evolution. More importantly, we found that Z-scheme is an effective strategy to improve the photocatalytic performance of carbon nanodots. The photocatalytic H2-evolution rates improve from 4.65 μmol g−1 h−1 to 1330 μmol g−1 h−1 under xenon lamp irradiation.

Pure carbon nanodots (CNDs) without any modification and co-catalyst can drive photocatalytic hydrogen generation. The hydrogen generation rate of CNDs reaches 3615.3 μmol g−1 h−1 when methanol was used as the sacrificial donor, which is 34.8 times higher than that of commercial Degussa P25 photocatalyst under the same conditions. Moreover, the CNDs show good stability; the hydrogen generation rate has negligible change even after four cycles of testing.

We report a new and effective method to prepare high activity graphitic carbon nitride (g-C3N4) by a simple ammonia etching treatment. The obtained g-C3N4 displays a high BET surface area and enhanced electron/hole separation efficiency. The hydrogen evolution rates improved from 52 μmol h(-1) to 316.7 μmol h(-1) under visible light.

Modulation of the TiO2 structure to achieve efficient photocatalytic usage of solar light is still a challenging issue. Here we report that simple bombardment of anatase TiO2 nanocrystals by hot molecules can alter its phase transformation kinetics and lead to the reconstruction of the resulting rutile surfaces into a metastable TiO2 crystalline structure. Moreover, the metastable surface crystalline phase is able to harvest visible light up to 480 nm, and exhibits good properties for photocurrent generation. Photocatalysis tests show that upon irradiation by visible light (λ > 420 nm), the surface-reconstructed TiO2 crystals display excellent and stable photocatalytic activity for hydrogen production from aqueous ethanol solution, with a hydrogen production rate of 302 μmol g−1 h−1. This finding might bring a new approach to kinetically tune the structure of TiO2 or other semiconductor crystals in order to modulate their properties.

We report a new method to prepare photoluminescent carbon nanoparticles (CNPs) by a light-induced process. The obtained CNPs are sensitive to the specific detection of Fe3+ with a detection limit of 0.55 ppm. CNPs also show excellent photocatalytic hydrogen production under xenon lamp irradiation. The hydrogen evolution rate is up to 4.89 μmol h−1 over 2.1 mg CNPs.

Melamine and cyanuric chloride self-assemble into CNH nanocages. The nanocages have uniform mesosized cages with micropores in the walls, which is beneficial to the diffusion and adsorption of O2, as well as to the rapid electrochemical catalysis of O2 into hydrogen peroxide. Moreover, theoretical calculations confirm that triangle-shaped micropores are the only adsorption sites and O2 is catalyzed in the center of the micropores.

Nitrogen-doped carbons with highly ordered macroporous structures are fabricated via the assembly and carbonization of polymethylmethacrylate (PMMA)–polyacrylonitrile (PAN) core–shell nanoparticles. During the carbonization, PMMA (acting as a template) is completely removed, and the resulting hollow PAN particles are fused to form ordered macroporous structures. Micropores are present on the macropore walls, providing desirable inter-macropore channels. The nitrogen atoms partially remain in the resulting carbon structures and exhibit mainly pyridinic and quaternary configurations under relatively high carbonization temperatures. The careful control of the pre-stabilization and carbonization conditions is crucially important for the formation of the ordered macroporous structures. As a demonstration, the obtained nitrogen-doped macroporous carbons exhibit excellent electrochemical catalytic activities both for the reduction of Sn2− electrolyte ions in QDSSCs and the reduction of oxygen in fuel cells.

The functions of nitrogen-doped hollow carbon nanoparticles (N-HCNPs) as counter electrodes in quantum dot sensitized solar cells (QDSSCs) have been studied in this paper. Electrochemical impedance spectroscopy (EIS) and Tafel-polarization tests reveal a low charge transfer resistance and a high exchange current density between polysulfide electrolyte and the N-HCNPs electrode. Cyclic voltammetry results indicate that the N-HCNPs electrode shows high electrocatalytic activity and excellent tolerance toward the S 2� /Sn 2� electrolyte. A power conversion efficiency of 2.67% is achieved for the QDSSCs based on N-HCNPs counter electrodes, which is clearly higher than those of the QDSSCs based on HCNPs, carbon nanotubes and Pt counter electrodes. The results reveal that the N-HCNPs electrode is a promising counter electrode candidate for QDSSCs.

The non-equilibrium quick oxidation of titanium nitride (TiN) particles is found to be capable of kinetically controlling the partial oxidation on the surface and constructing a TiOxNy@TiN core–shell structure, in which the TiOxNy shell exhibits different components (x = 0.0–2.0). The TiOxNy@TiN structure can absorb visible light and display a high photocatalytic activity for hydrogen production, without any help from noble metal co-catalysts. A hydrogen generation rate of 506 μmol g−1 h−1 can be reached. The strong catalytic ability of TiOxNy@TiN can be attributed to the formation of heterojunction among the hybrid TiOxNy, which can facilitate the separation of light-induced electron–hole pairs. Furthermore, the non-equilibrium quick oxidation leads to the partial survival of electro-conductive TiN tiny crystals on the surface, which can act as co-catalysts to further improve the electron–hole separation and to catalyze hydrogen ion reduction.

The modulation of TiO2 structure can effectively alter the oxidation kinetics and pathway of sacrificial ethanol during the water-splitting reaction and dramatically adjust the selectivity of the valuable coupling product 2,3-butanediol from 0.0% to 96.6%, showing the possibility of photohydrogen production in green and economical indexes.

Free-standing graphene-based macroscopic membranes, which are characterized by a layered structure and tunable conductivity, are prepared by a self-assembly process at a liquid–air interface. Since the preliminary results indicate that it is hard to construct macroscopic graphene membranes solely by low-temperature exfoliated graphene nanosheets (LGNs) at the liquid–air interface, graphene oxide nanosheets (GONs), as the stacking template and sticking component, are introduced into the assembly process of graphene layers to promote the formation of layer-by-layer stacking structure and help form a conductive macroscopic membrane. The conductivity of such a graphene-based membrane can be tuned by changing the GON fraction in the LGN/GON hybrid membrane.

Hollow carbon nanoparticles that have been highly doped with nitrogen (N-HCNPs) are directly prepared by a facile one-pot method based on the detonation-assisted chemical vapor deposition of dimethylformamide without the use of metal catalysts. The N-HCNPs exhibit uniform core-shell microstructures with inner cavities encapsulated by graphitic walls, possessing a narrow size distribution of 10–25 nm. The nitrogen content in N-HCNPs is as high as 20.8% atom ratio, and the nitrogen bonds display pyridine-, pyrrole-, and graphite-like configurations. Defects and dislocations are present in the graphene layers due to highly incorporated nitrogen, leading to the creation of micropores on the carbon shell and a large BET surface area of 454 m2 g−1. The unique N-HCNPs with interconnected hierarchical porous structures and nitrogen-containing defects show excellent electrocatalytic activity for triiodide reduction in dye-sensitized solar cells, superior to conventional platinum catalysts.

Multi-wall carbon nanotubes can readily form by the catalysis of lanthanide oxides. The formed tubes are unusually separated from the catalyst particles, which leads to a straightforward identification of the self-assembly of carbon particles that is hidden in the chaotic carbon-catalyst-hybrid system of catalytic carbon nanotube evolution. Following the identified self-assembly concept, conventional bulk activated carbon (AC) has been successfully transformed into CNTs through a detonation-induced cracking of AC and a real-time re-organization.