Recent catalytic applications of MXene-based layered nanomaterials.

The urgent issues related to the catalytic processes and energy applications have accelerated the development of hybrid and smart materials. MXenes are a new family of atomic layered nanostructured materials that require considerable research. Tailorable morphologies, strong electrical conductivity, great chemical stability, large surface-to-volume ratios, tunable structures, among others are some significant characteristics that make MXenes appropriate for various electrochemical reactions, including dry reforming of methane, hydrogen evolution reaction, methanol oxidation reaction, sulfur reduction reaction, Suzuki-Miyaura coupling reaction, water-gas shift reaction, and so forth. MXenes, on the other hand, have a fundamental drawback of agglomeration, as well as poor long-term recyclability and stability. One possibility for overcoming the restrictions is the fusion of nanosheets or nanoparticles with MXenes. Herein, the relevant literature on the synthesis, catalytic stability and reusability, and applications of several MXene-based nanocatalysts are deliberated including the merits and cons of the newer MXene-based catalysts.

Pyrolysis of fast-growing aquatic biomass -Lemna minor (duckweed): Characterization of pyrolysis products.

The aim of this work was to conduct the experimental study of pyrolysis of fast-growing aquatic biomass -Lemna minor (commonly known as duckweed) with the emphasis on the characterization of main products of pyrolysis. The yields of pyrolysis gas, pyrolytic oil (bio-oil) and char were determined as a function of pyrolysis temperature and the sweep gas (Ar) flow rate. Thermogravimetric/differential thermogravimetric (TG/DTG) analyses of duckweed samples in inert (helium gas) and oxidative (air) atmosphere revealed differences in the TG/DTG patterns obtained for duckweed and typical plant biomass. The bio-oil samples produced by duckweed pyrolysis at different reaction conditions were analyzed using GC-MS technique. It was found that pyrolysis temperature had minor effect on the bio-oil product slate, but exerted major influence on the relative quantities of the individual pyrolysis products obtained. While, the residence time of the pyrolysis vapors had negligible effect on the yield and composition of the duckweed pyrolysis products.

Hydrogen production via photolytic oxidation of aqueous sodium sulfite solutions.

Sulfur dioxide (SO(2)) emission from coal-burning power plants and refinery operations has been implicated as a cause of acid rain and other air pollution related problems. The conventional treatment of SO(2)-contaminated air consists of two steps: SO(2) absorption using an aqueous sodium hydroxide solution, forming aqueous sodium sulfite (Na(2)SO(3)), and Na(2)SO(3) oxidation via air purging to produce sodium sulfate (Na(2)SO(4)). In this process, the potential energy of SO(2) is lost. This paper presents a novel ultraviolet (UV) photolytic process for production of hydrogen from aqueous Na(2)SO(3) solutions. The results show that the quantum efficiency of hydrogen production can reach 14.4% under illumination from a low pressure mercury lamp. The mechanism occurs via two competing reaction pathways that involve oxidation of SO(3)(2-) to SO(4)(2-) directly and through the dithionate (S(2)O(6)(2-)) ion intermediate. The first route becomes dominant once a photostationary state for S(2)O(6)(2-) is established. The initial pH of Na(2)SO(3) solution plays an important role in determining both the hydrogen production rate and the final products of the photolytic oxidation. At initial solution pH of 9.80 Na(2)SO(3) photo-oxidation generates Na(2)SO(4) as the final reaction product, while Na(2)S(2)O(6) is merely a reaction intermediate. The highest hydrogen production rate occurs when the initial solution pH is 7.55. Reduction in the initial solution pH to 5.93 results in disproportionation of HSO(3)(-) to elemental sulfur and SO(4)(2-) but no hydrogen production.