Photocatalytic Synthesis of Ammonia from Hollow Coral-Like Graphitic Carbon Nitride/FeOCl Loaded with Fe-1T MoS2 Nanosheets as Cocatalysts

Photocatalytic ammonia synthesis (PAS) represents an emerging environmentally friendly approach to ammonia production. In this work, we employed Fe doping to modify the cocatalyst 1T MoS2, enhancing the active N2 sites on Fe-1T MoS2 by inducing defects on the surface of 1T MoS2. Afterward, Fe-1T MoS2 was loaded onto a hollow coral-like graphitic carbon nitride (CCN)/FeOCl composite. Under simulated sunlight, the efficiency of 5% Fe-1T MoS2@CCN/FeOCl (Fe-MCN/FeOCl) reached 367.62 μmol g-1 h-1, surpassing 1T MoS2@CCN(MCN) by 3.2 times, CCN by 16.9 times, and g-C3N4 by 32.5 times, where 5% means the doping amount of Fe in 1T MoS2. The good performance of Fe MCN/FeOCl should be attributed to the Fe doping in Fe-MCN/FeOCl which not only increases the separation efficiency of active sites and charge carriers, but also reduces the sample impedance significantly through the heterojunction formed between CCN and FeOCl. This work also presents a method for creating more efficient and stable photocatalysts for ammonia synthesis.

Integrating bimetallic borides with g-C3N4 containing cyanamide defects for efficient photocatalytic nitrogen fixation

The sustainable generation of ammonia by photocatalytic nitrogen fixation under mild conditions is fascinating compared to conventional industrial processes. Nevertheless, owing to the low charge transfer efficiency, the insufficient light absorption capacity and limited active sites of the photocatalyst cause the difficult adsorption and activation of N2 molecules, thereby resulting in a low photocatalytic conversion efficiency. Herein, a novel bimetallic CoMoB nanosheets (CoMoB) co-catalyst modified carbon nitride with dual moiety defects (CN-TH3/3) Schottky junction photocatalyst is designed for photocatalytic nitrogen reduction reaction (NRR). The photocatalytic nitrogen reduction rate of the optimized CoMoB/CN-TH3/3 photocatalyst is 4.81 mM·g-1·h-1, which is 6.2 and 2.2 times higher than carbon nitride (CN) (0.78 mM·g-1·h-1) and CN-TH3/3 (2.21 mM·g-1·h-1), respectively. The excellent photocatalytic NRR performance is ascribed not only to the introduction of dual moiety defects (cyano and cyanamide groups) that extends the visible light absorption range and promotes exciton polarization dissociation, but also to the formation of interfacial electric field between CoMoB and CN-TH3/3, which effectively facilitates the interfacial charge transfer. Thus, the synergistic interaction between CN-TH3/3 and CoMoB further increases the electron numble of CoMoB active sites, which effectively strengthens the adsorption and activation of N2 and weakens the NN triple bond, thereby enhancing the photocatalytic NRR activity. This work highlights the introduced dual moiety defects and bimetallic CoMoB co-catalyst to synergistically enhance the photocatalytic nitrogen reduction performance.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation

In nature, biological nitrogen fixation is accomplished through the π-back-bonding mechanism of nitrogenase, which poses significant challenges for mimic artificial systems, thanks to the activation barrier associated with the N≡N bond. Consequently, this motivates us to develop efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions. We employ a charge-assisted self-assembly process toward encapsulating one polyoxometalate (POM) within a dehydrated Zr-based metal-organic framework (d-UiO-66) exhibiting nitrogen photofixation activities, thereby constructing an enzyme-mimicking photocatalyst. The dehydration of d-UiO-66 is favorable for facilitating nitrogen chemisorption and activation via the unpaired d-orbital electron at the [Zr6O6] cluster. The incorporation of POM guests enhanced the charge separation in the composites, thereby facilitating the transfer of photoexcited electrons into the π* antibonding orbital of chemisorbed N2 for efficient nitrogen fixation. Simultaneously, the catalytic efficiency of SiW9Fe3@d-UiO-66 is enhanced by 9.0 times compared to that of d-UiO-66. Moreover, SiW9Fe3@d-UiO-66 exhibits an apparent quantum efficiency (AQE) of 0.254% at 550 nm. The tactics of "working-in-tandem" achieved by POMs and d-UiO-66 are extremely vital for enhancing artificial ammonia synthesis. This study presents a paradigm for the development of an efficient artificial catalyst for nitrogen photofixation, aiming to mimic the process of biological nitrogen fixation.

Mechanism of melanogenesis inhibition by Keggin-type polyoxometalates

Abnormal melanin overproduction can result in hyperpigmentation syndrome in human skin diseases and enzymatic browning of fruits and vegetables. Recently, our group found that Keggin-type polyoxometalates (POMs) can efficiently inhibit tyrosinase activity. However, it remains unclear whether Keggin-type POMs exhibit optimal effects in vivo. Additionally, the inhibitory effect and mechanism of action of POMs on cellular tyrosinase activity and melanogenesis have been rarely reported. Here we demonstrate that our screened and synthesised PMo11Zn and GaMo12 show superior inhibitory effects on melanin formation as well as inhibition of cellular tyrosinase activity compared to other Keggin-type POMs. Intriguingly, we reveal that Keggin-type POMs competitively bind to tyrosinase mainly through more interactions with Cu2+ ions and the amino acid residue is capable of forming van der Waals, cation-π and hydrogen bonds, resulting in a reversible non-covalent complex formation. Our findings provide valuable insights into the design, synthesis and screening of polyoxometalates as multifunctional metallodrugs and food preservatives against hyperpigmentation.

One-step synthesis of MoS2/NiS heterostructures with a stable 1T phase for an efficient hydrogen evolution reaction

Metallic phase (1T) MoS₂ has been regarded as an ideal catalytic material for the hydrogen evolution reaction (HER) due to its high active site density and favorable electrical conductivity. However, the preparation of 1T-phase MoS₂ samples requires tough reaction conditions and 1T-MoS₂ has poor stability under alkaline conditions. In this work, 1T-MoS₂/NiS heterostructure catalysts grown in situ on carbon cloth were prepared by a simple one-step hydrothermal method. The obtained MoS₂/NiS/CC combines the advantages of high active site density and a self-supporting structure, achieving stable 77% metal phase (1T) MoS₂. The combination of NiS and 1T-MoS₂ enhances the intrinsic activity of MoS₂ while the electrical conductivity is improved. These advantages enable the 1T-MoS₂/NiS/CC electrocatalyst to have a low overpotential of 89 mV (@10 mA cm^-2) and a small Tafel slope of 75 mV dec^-1 under alkaline conditions and provide a synthetic strategy of stable 1T-MoS₂-based electrocatalysts for the HER by a heterogeneous structure.

Wheel-shaped molybdenum(v) cobalt-phosphate cluster as a highly sensitive bifunctional photoelectrochemical sensor for the trace determination of Cr(vi) and tetracycline

A wheel-shaped {Co16Mo16P24} cluster-based 3-D crystal framework serves as an efficient bifunctional photoelectrochemical sensor for the trace determination of Cr(vi) and tetracycline.