Layered High-Entropy Metallic Glasses for Photothermal CO2 Methanation.

High entropy alloys and metallic glasses, as two typical metastable nanomaterials, have attracted tremendous interest in energy conversion catalysis due to their high reactivity in nonequilibrium states. Herein, a novel nanomaterial, layered high entropy metallic glass (HEMG), in a higher energy state than low-entropy alloys and its crystalline counterpart due to both the disordered elemental and structural arrangements, is synthesized. Specifically, the MnNiZrRuCe HEMG exhibits highly enhanced photothermal catalytic activity and long-term stability. An unprecedented CO2 methanation rate of 489 mmol g-1 h-1 at 330 °C is achieved, which is, to the authors' knowledge, the highest photothermal CO2 methanation rate in flow reactors. The remarkable activity originates from the abundant free volume and high internal energy state of HEMG, which lead to the extraordinary heterolytic H2 dissociation capacity. The high-entropy effect also ensures the excellent stability of HEMG for up to 450 h. This work not only provides a new perspective on the catalytic mechanism of HEMG, but also sheds light on the great catalytic potential in future carbon-negative industry.

Photocatalytic nitrogen fixation of metal-organic frameworks (MOFs) excited by ultraviolet light: insights into the nitrogen fixation mechanism of missing metal cluster or linker defects.

The vacancies of semiconductors have proven to be effective active sites for photocatalytic nitrogen fixation, but what about the role of defects in MOF materials? Herein, we report the first UiO-66 with photo-excited cluster defects and linker defects for photocatalytic nitrogen fixation. It was determined through the post-synthetic ligand exchange (PSE) process that the linker defects, rather than cluster defects, can greatly improve the performance, which is due to linker defects forming unsaturated metal nodes such as the vacancy in a semiconductor. Specifically, for photo-activated UiO-66, the NH4+ production rate was 196 and 68 µmol g-1 h-1 in air atmosphere under ultraviolet-visible (UV-Vis) and visible light, respectively. This report provides a new effective strategy to design efficient nitrogen fixation photocatalysts.

Recent advances in photocatalytic nitrogen fixation: from active sites to ammonia quantification methods.

Photocatalytic nitrogen fixation has become a hot topic in recent years due to its mild and sustainable advantages. While modifying the photocatalyst to enhance its electron separation, light absorption and nitrogen reduction abilities, the role of the active sites in the catalytic reaction cannot be ignored because the N[triple bond, length as m-dash]N nitrogen bond is too strong to activate. This review summarizes the recent research on nitrogen fixation, focusing on the active sites for N2 on the catalyst surface, classifying common active sites, explaining the main role and additional role of the active sites in catalytic reactions, and discussing the methods to increase the number of active sites and their activation ability. Finally, the outlook for future research is presented. It is hoped this review could help researchers understand more about the activation of the nitrogen molecules and lead more efforts into research on nitrogen fixation photocatalysts.

In situ modification of cobalt on MXene/TiO2 as composite photocatalyst for efficient nitrogen fixation.

Modulation of the binding of the reactant or product species with catalysts is an effective approach to optimize the photocatalytic activity. Herein, we explored the relationship between the binding of reactant (N2) and product (NH3) with catalyst and the photocatalytic nitrogen fixation activity. The surface reactivity of nitrogen with water was tuned by introducing Co into the MXene@TiO2 catalysts, which the TiO2 nanoparticle derived from the in-situ growth on the surface of MXene nanosheets. Co modified adjusted the chemisorption equilibrium of the catalyst for reactant (N2) and product (NH3), thus promoted product desorption and efficiency of the active site. Remarkably, the optimal catalyst (MXene/TiO2/Co-0.5%) exhibited outstanding NH4+ production rate (110 µmol g-1 h-1) and excellent stability in pure water without any hole sacrificial agent under Ultraviolet-Visible (UV-vis) light in N2 and air ambient.