Upconversion hollow nanospheres CeF3 co-doped with Yb3+ and Tm3+ for photocatalytic nitrogen fixation

Boosting Electrochemical Nitrogen Fixation via Regulating Surface Electronic Structure by CeO2 Hybridization

Electrocatalytic nitrogen reduction reaction (NRR) paves a sustainable way to produce NH3 but suffering from the relatively low NH3 yield and poor selectivity. High-performance NRR catalysts and a deep insight into the structure-performance relationship are higher desired. Herein, a molten-salt approach is developed to synthesize tiny CeO2 nanoparticles anchored by ultra-thin MoN nanosheets as advanced catalysts for NRR. Specifically, a considerably high NH3 yield rate of 27.5 µg h-1 mg-1 with 17.2% Faradaic efficiency (FE) can be achieved at -0.3 V vs (RHE) under ambient conditions. Experimental and density functional theory (DFT) calculations further point out that the incorporation of MoN with CeO2 can promotes the enlargement of the electron deficient area of nitrogen vacancy site. The enlarged electron deficient area contributes to the accommodation of lone pair electrons of N2, which dramatically improves the N2 adsorption/activation and the key intermediates (*NNH and *NH3) generation, thus boosting the NRR performance.

Near-infrared light-driven asymmetric photolytic reduction of ketone using inorganic-enzyme hybrid biocatalyst

Effective photolytic regeneration of the NAD(P)H cofactor in enzymatic reductions is an important and elusive goal in biocatalysis. It can, in principle, be achieved using a near-infrared light (NIR) driven artificial photosynthesis system employing H2O as the sacrificial reductant. To this end we utilized TiO2/reduced graphene quantum dots (r-GQDs), combined with a novel rhodium electron mediator, to continuously supply NADPH in situ for aldo-keto reductase (AKR) mediated asymmetric reductions under NIR irradiation. This upconversion system, in which the Ti-O-C bonds formed between r-GQDs and TiO2 enabled efficient interfacial charge transfer, was able to regenerate NADPH efficiently in 64 % yield in 105 min. Based on this, the pharmaceutical intermediate (R)-1-(3,5-bis(trifluoromethyl)phenyl)ethan-1-ol was obtained, in 84 % yield and 99.98 % ee, by reduction of the corresponding ketone. The photo-enzymatic system is recyclable with a polymeric electron mediator, which maintained 66 % of its original catalytic efficiency and excellent enantioselectivity (99.9 % ee) after 6 cycles.

Hollow Spherical Heterostructured FeCo-P Catalysts Derived from MOF-74 for Efficient Overall Water Splitting

The design of catalysts with tunable active sites in heterogeneous interface structures is crucial for addressing challenges in the water-splitting process. Herein, a hollow spherical heterostructure FeCo-P is successfully prepared by hydrothermal and phosphorization methods. This hollow structure, along with the heterogeneous interface between Co2 P and FeP, not only facilitates the exposure of more active sites, but also increases the contact area between the catalyst and the electrolyte, as well as shortens the distance for mass/electron transfer. This enhancement promotes electron transfer to facilitate water decomposition. FeCo-P exhibits excellent hydrogen evolution (HER) and oxygen evolution (OER) performance when reaching @ 10 mA cm-2 in 1 mol L-1  KOH, with overpotentials of 131/240 mV for HER/OER. Furthermore, when FeCo-P is used as both the cathode and anode for overall water splitting (OWS), it only requires low voltages of 1.49, 1.55, and 1.57 V to achieve CDs of 10, 100, and 300 mA cm-2 , respectively. Density functional theory calculations indicate that constructing a Co2 P and FeP heterogeneous interface with good lattice matching can facilitate electron redistribution, thereby enhancing the electrocatalytic performance of OWS. This work opens up new possibilities for the rational design of efficient water electrolysis catalysts derived from MOFs.

Doping rare earth cations with an additional chemical reduction synergistically weakened the photocatalytic performance of ceria

Chemical reducing or rare earth cations (RE) doping was normally employed to promote the photocatalytic performance of ceria, aimed to evaluate their cooperation influences, ceria was obtained by decomposing homogenously RE (RE = La, Sm, and Y)-doped CeCO₃OH in H₂. XPS and EPR results evidenced that the excess oxygen vacancies (OVs) were formed in RE-doped CeO₂ compared to the un-doped ceria. However, all the RE-doped ceria unexpectedly showed an impeded photocatalytic activity towards to methylene blue (MB) photodegradation. The 5% Sm-doped ceria had the best MB photodegradation ratio of 81.47% after 2-h reaction in all RE-doped samples, which was lower than that of 87.24% for the un-doped ceria. After doping RE cations and chemical reducing, the band gap of ceria were almost narrowed, while the PL spectra and photo-electro characterizations indicated that the separation efficiency of photo-excited e^-/h⁺ (electrons/holes) was reduced. The RE dopants and formed excess OVs including inner and surface OVs was proposed to promote the recombination of e^-/h⁺ which further hindered the generation of active species of ·O₂^- and ·OH, and finally weakened the photocatalytic activity of ceria.

Collaborative influence of morphology tuning and RE (La, Y, and Sm) doping on photocatalytic performance of nanoceria

Tuning morphology and doping additional rare earth (RE) cations are potential techniques to promote the photocatalytic performance of ceria (CeO₂), evaluating the collaborative effects of morphology and RE dopants is significant for producing high active ceria-based catalysts. So in this work, cubic, polyhedral and rod-like nanoceria doped with 10 mol % La (lanthanum), Y (yttrium), or Sm (samarium) were synthesized by a facile template-free hydrothermal method. Phases, morphologies, oxygen vacancies (OVs) concentration, energy band structure, photo-carriers separation/recombination, and photodegradation ratio toward methylene blue (MB) dye of as prepared ceria were studied. Results show that doped CeO₂ maintains a similar morphology structure with un-doped sample and the band gap narrows slightly. Y-doped nanoceria, with an improved separation and a reduced recombination of photo-excited electrons (e^-) and holes (h⁺), owns a higher MB photodegradation ratio than that of samples doping with La or Sm, which is measured as 79.04, 84.43, and 85.59% for Y-doped cubic, polyhedral, and rod-like CeO₂. The collaborative influence of morphology tuning and RE (La, Y, and Sm) doping on photocatalytic performance of nanoceria includes the effects of doped elements and the formation of OVs. The elevation of OVs concentration as well as the separation efficiency of photo-generated e^-/h⁺ are suggested to further enhance the photocatalytic performance of ceria.

Exploiting the upconversion luminescence, Lewis acid catalytic and photothermal properties of lanthanide-based nanomaterials for chemical and polymerization reactions

Lanthanide-based nanocrystals possess three unique physical properties that make them attractive for facilitating photoreactions, namely photon upconversion, Lewis acid catalytic activity and photothermal effect. When co-doped with suitable sensitizer and...

N-doping TiO2 hollow microspheres with abundant oxygen vacancies for highly photocatalytic nitrogen fixation

Photocatalytic fixation of nitrogen to ammonia (NH₃) is a green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N₂ and the band position of TiO₂ are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO₂ hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol g_cat^-1h^-1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H₂O₂ treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol g_cat^-1h^-1 after reducing oxygen vacancies by H₂O₂ treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol g_cat^-1h^-1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.