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Photocatalytic H2O2 production is an eco-friendly technique because only H2O, molecular O2 and light are involved. However, it still confronts the challenges of the unsatisfactory productivity of H2O2 and the dependence on organic electron donors or high purity O2, which restrict the practical application. Herein, we construct a type-II heterojunction of the protonated g-C3N4 coated Co9S8 semiconductor for photocatalytic H2O2 production. The ultrathin g-C3N4 uniformly spreads on the surface of the dispersed Co9S8 nanosheets by a two-step method of protonation and dip-coating, and exhibits improved photogenerated electrons transportability and e--h+ pairs separation ability. The photocatalytic system can achieve a considerable productivity of H2O2 to 2.17 mM for 5 h in alkaline medium in the absence of the organic electron donors and pure O2. The optimal photocatalyst also obtains the highest apparent quantum yield (AQY) of 18.10% under 450 nm of light irradiation, as well as a good reusability. The contribution of the type-II heterojunction is that the migrations of electrons and holes within the interface between g-C3N4 and Co9S8 matrix promote the separation of photocarriers, and another channel is also opened for H2O2 generation. The accumulated electrons in conduction band (CB) of Co9S8 contribute to the major channel of two-electron reduction of O2 for H2O2 production. Meanwhile, the electrons in CB of g-C3N4 participate in the single electron reduction of O2 as an auxiliary channel to enhance the H2O2 production.

RESUMEN

For the simultaneous photocatalytic reduction of hexavalent chromium (Cr(VI)) and the degradation of rhodamine B (RhB), directional charge-transfer channels and efficient separation of photogenerated holes and electrons are important. Herein, a Z-scheme heterojunction photocatalyst, protonated g-C3N4/BiVO4 decorated with wood flour biochar (pCN/WFB/BiVO4), was prepared through a hydrothermal reaction and electrostatic self-assembly for Cr(VI) photoreduction and RhB photodegradation. The morphological features, crystalline structure, chemical composition, optical properties, specific surface area, and photoelectrochemical properties of the prepared samples were investigated. The pCN/WFB/BiVO4 photocatalyst exhibited superior removal performance when used to remove Cr(VI) and RhB separately or RhB-Cr(VI) system. The biochar bridge served as a charge-transfer channel between two semiconductors, and the electrons in protonated g-C3N4 (pCN) and BiVO4 achieved a charge balance. This led to the formation of a Z-scheme heterojunction, fast photogenerated charge separation, and a powerful redox ability. The pCN/WFB/BiVO4 photocatalyst provides new insight into the mechanisms responsible for boosting multicomponent photocatalytic reactions, while constituting a promising candidate for wastewater treatment.

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RESUMEN

A dye-sensitive photocatalytic H2 evolution reaction (HER) system with photogenerated carrier directed conduction was constructed. The protonated g-C3N4 combines with the sheet-like Co MOF to form a 2D/2D heterojunction via electrostatic self-assembly. The protonated g-C3N4 and 2D Co-MOF directionally adsorb Eosin Y (EY) and triethanolamine (TEOA) molecules through hydrogen bond and complexation to achieve a whole photocatalytic system. The integral structure effectively facilitates the utilization of dye sensitizer and hole sacrificial agent to achieve the effective and stable photocatalytic H2 evolution capacity. The photocatalytic hydrogen evolution rate of g-C3N4 after protonation is 1.88 times as high as that of the original g-C3N4. On the basis of 2D/2D heterojunction, Co MOF is doped with rare earth element Sm. The 4f electrons and the difference valences (Sm3+ and Co2+) further suppress the reorganization of photogenerated excitons to achieve highly efficient photocatalytic HER. The directional coupling of sensitizer and electron sacrificial agent combined with rare earth element doping makes the photocatalytic HER rate of the composite material reached 73.42 µmol.h-1 within 5 h under simulated sunlight.

RESUMEN

Recently, photocatalytic NOx treatment has attracted great attention on account of the use of environmental-friendly and tremendous energy source. However, the difficult recovery of most reported powdery photocatalysts and the high generation rate of toxic NO2 byproduct limit its application. Here, we designed a novel monolithic protonated g-C3N4/graphene oxide aerogel through a direct frozen-drying method. A remarkable surface electric charge change of negative g-C3N4 to positive protonated g-C3N4 can be observed after the protonating treatment, which connects with negative graphene oxide nanosheets through the formation of strong electrostatic self-assembly to accelerate the photogenerated charge carriers transfer. Graphene oxide aerogel acts as a monolithic substrate, which provides abundant porous structure, enhanced visible-light absorption, and electrons transport pathway to improve photocatalytic activity. Importantly, the introduction of H atoms on the N atoms of p-C3N4 promotes the activation of oxygen atoms, thus improving the oxidization of NO2 to nitrate. As a result, protonated g-C3N4/graphene oxide aerogel reveals an excellent NO removal ratio (46.1%) and low NO2 generation (2.4%), demonstrating its excellent promising for air pollution purification. Our current work affords novel innovative insight for the construction of monolithic photocatalysts to control the secondary pollution for environmental remediation.

RESUMEN

DNA formylation (5-formylcytosine, 5fC) is a major epigenetic modification involved in alterations in the DNA double helix structure and protein identification. Due to the low amount in all mammalian tissues and cells, it is necessary to develop a rapid, sensitive and efficient method for detecting 5fC for further understanding the biological functions of 5fC. Thus, a novel PEC biosensor was constructed using P-g-C3N4-WS2 nanocomposite as photoactive material. Firstly, AuNPs/P-g-C3N4-WS2/ITO electrode was prepared as substrate electrode. Secondly, the probe DNA and complementary DNA (containing 5fC base) was modified to the electrode surface based on the formation of Au-S bonds between AuNPs and thiol group on the probe DNA and hybridization, respectively. Finally, the amino functionalized MnO2 nanoflowers were further modified to the electrode surface by covalent interaction between the aldehyde group on the 5fC and the amino group on MnO2 nanoflowers. The sensitive and specific detection of 5fC can be achieved by oxidizing ascorbic acid with MnO2 nanoflowers and quenching the photoactivity of P-g-C3N4-WS2 nanocomposite. The sensor has a detection range of 0.01-200 nM and a detection limit of 3.8 pM. Moreover, this sensor has excellent detection specificity, stability and reproducibility.

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