Equilibrium unconstrained low-temperature CO2 conversion on doped gallium oxides by chemical looping.

Reverse water gas shift (RWGS) can convert CO2 into CO by using renewable hydrogen. However, this important reaction is endothermic and equilibrium constrained, and thus traditionally performed at 900 K or higher temperatures using solid catalysts. In this work, we found that RWGS can be carried out at low temperatures without equilibrium constraints using a redox method called chemical looping (CL), which uses the reduction and oxidation of solid oxide surfaces. When using our developed MGa2Ox (M = Ni, Cu, Co) materials, the reaction can proceed with almost 100% CO2 conversion even at temperatures as low as 673 K. This allows RWGS to proceed without equilibrium constraints at low temperatures and greatly decreases the cost for the separation of unreacted CO2 and produced CO. Our novel gallium-based material is the first material that can achieve high conversion rates at low temperatures in reverse water gas shift using chemical looping (RWGS-CL). Ni outperformed Cu and Co as a dopant, and the redox mechanism of NiGa2Ox is a phase change due to the redox of Ga during the RWGS-CL process. This major finding is a big step forward for the effective utilization of CO2 in the future.

Z-scheme MoS2/Co3S4@PEG nanoflowers: Intracellular NIR-II photocatalytic O2 production facilitating hypoxic tumor therapy.

Intratumoral hypoxia, which is in favour of cancer cell proliferation, invasion and metastasis, also inhibits photodynamic therapy (PDT) badly. Herein, second near-infrared (NIR-II) photocatalytic O2 production is established to realize hypoxia relief. MoS2/Co3S4@PEG (MSCs@PEG) nanoflowers (100-150 nm) are prepared via a two-step hydrothermal method. These samples possess high NIR-II harvest and photothermal conversion (39.8 %, 1064 nm) ability. That not only reveals photothermal therapy (PTT) but also lifts the thermal energy of nanomaterials to replenish extra energy, making sure the co-excitation of MoS2 (1.14 eV) and Co3S4 (1.40 eV) by low-energy NIR-II (1064 nm, 1.16 eV) laser. The investigation of band structure further displays the Z-Scheme characterization of MSCs heterostructure. These photo-excited holes/electrons hold great redox ability to form O2 (water splitting) and reactive oxygen species (ROS), simultaneously. In addition, MSC-2@PEG can be served to mimic catalase, peroxidase, and glutathione (GSH) oxidase to further boost oxidative stress. It is noted that heterostructure discovers the greater nanozyme activity, attributing to the lower resistance for charge transfer. Moreover, MSC-2@PEG displays a novel biodegradation ability to induce the elimination via urine and faeces within 14 days. Given the superparamagnetic and photothermal effect, the nanocomposite can be used as magnetic resonance and photothermal imaging (MRI and PTI) contrast. Associated with dual-imaging, intracellular O2 supplementation, and synergistic chemotherapy (CDT)/PTT/PDT, MSC-2@PEG possess great tumor inhibition that also efficiently motivates immune response for anticancer.

NIR-II-driven intracellular photocatalytic oxygen-generation on Z-Scheme iron sulfide/cobalt sulfide nanosheets for hypoxic tumor therapy.

Tumor hypoxia not only promotes the proliferation, invasion and metastasis of cancer cells but also seriously hinders photodynamic therapy (PDT). Here, second near-infrared (NIR-II) photocatalytic O2 generation is introduced to relieve hypoxia. FeS2/CoS2@PEG (FCs@PEG) nanosheets (∼80 nm) are prepared with Fe-Co layered double hydroxides (LDHs) as precursor. As-synthesized samples have great NIR-II harvest and photothermal conversion efficiency (50.5 %, 1064 nm). In addition, photothermal effect can elevate the thermal energy of nanocomposite to supply extra energy and to excite FeS2 (1.16 eV) and CoS2 (1.37 eV) simultaneously by low-energy NIR-II (1064 nm, 1.16 eV) irradiation. Band structure is further investigated to discover the Z-Scheme mechanism of FCs@PEG, whose photogenerated charges remains high redox potential to oxidize water forming O2 and to capture O2 producing reactive oxygen species (ROS), respectively. In addition, FC2@PEG enhances peroxidase and catalase activities attributing to the lower resistance for charge transfer in heterostructure. Besides, the nanocomposite also can be used as glutathione oxidase (GSHOD) to deplete GSH and break intracellular redox balance, facilitating oxidative stress. Most importantly, FC2@PEG reveals excellent biodegradation and elimination via feces and urine within 14 D. FCs@PEG integrate magnetic resonance and photothermal imaging (MRI and PTI), O2 in situ supply, and synergistic photothermal therapy (PTT)/PDT/chemotherapy (CDT) to arouse immune response for anticancer.

Insights into the co-doping effect of Fe3+ and Zr4+ on the anti-K performance of CeTiOx catalyst for NH3-SCR reaction.

A novel K-resistant Fe3+ and Zr4+ co-doped CeTiOx catalyst was first prepared by co-precipitation method for the ammonia-selective catalytic reduction (NH3-SCR) of NOx. On the premise of retaining the outstanding catalytic activity of CeTiOx catalyst, Fe3+ and Zr4+ co-doping efficiently improves its K-resistance with superior NOx conversion up to 84% after K-poisoning. Specially, the grain growth during the second calcination after K poisoning is successfully inhibited by Fe3+ and Zr4+ co-doping. Consequently, the large specific surface area with increased acid sites and efficiently retained reducibility over K-poisoned FeZrCeTiOx catalyst are realized, which prompt NH3 activation and NO oxidation, further benefit NH3-SCR. Besides, NH3-SCR reaction over CeTiOx and FeZrCeTiOx catalysts follows a possible L-H mechanism, and K-poisoning makes no change to it. Finally, a reasonable anti-K poisoning mechanism of FeZrCeTiOx catalyst is proposed: the excellent K-resistance is attributed to part of Fe and Zr are sacrificed to form Fe-O-K and Zr-O-K species protecting the active site Ce-O-Ti from K-poisoning, as well as the additional reducibility and surface acidity brought from Fe-O species with Zr prompting its uniform distribution.

Enhancing the K resistance of CeTiOx catalyst in NH3-SCR reaction by CuO modification.

It is generally accepted that CeTiOx catalyst owns outstanding catalytic activity for ammonia-selective catalytic reduction (NH3-SCR), but the tolerance to alkali metals is still dissatisfactory. Thus, it is of great importance to further elevate the catalytic activity and resistance to alkali metals of CeTiOx catalyst. In our work, a series of CeTiOx, CuO/CeTiOx, K-CeTiOx and K-CuO/CeTiOx catalysts were prepared to comprehensively analyze the influence of CuO modification on the physicochemical features, catalytic activity and anti-K ability of CeTiOx catalyst. The results manifest that CuO modification effectively enhances low-temperature catalytic activity and anti-K poisoning ability of CeTiOx catalyst by protecting the reduction ability and the surface acidity as well as weakening the adsorption strength of NOx.