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Molybdenum telluride nanosheets electrically reduce oxygen to produce hydrogen peroxide

wallpapers Tech 2021-01-20
Currently, more than 99% of H2O2 is produced through the high energy consumption and polluting anthraquinone oxidation pathway. In recent years, the method of reducing oxygen through the two-electron pathway (2e-ORR) to produce H2O2 has attracted attention. However, the existing catalysts in this pathway are either expensive (noble metal catalysts) or only suitable for alkaline conditions (H2O2 in alkali Unstable under sexual conditions). Therefore, 2e-ORR non-noble metal catalysts with high activity and high selectivity under acidic conditions are still to be developed.
Recently, a professor from Soochow University, China, in collaboration with a professor from the University of Chinese Academy of Sciences and a professor from Nanjing Normal University, discovered that liquid-phase stripped molybdenum telluride (MoTe2) nanosheets can be used as high-efficiency 2e-ORR catalysts in acid electrolytes and revealed its high activity, The key to high selectivity: The zigzag edge of the MoTe2 nanosheet has strong adsorption of the reaction intermediate HOO*, and weak adsorption of O*.
MoTe2 nanosheets are prepared from top to bottom through the liquid phase exfoliation method. XRD and Raman results show that the MoTe2 nanosheets obtained by exfoliation belong to the hexagonal 2H phase. SEM and TEM pictures prove the successful peeling of MoTe2 nanosheets. TEM statistics show that the size of the nanosheets is between 50-350 nm and the average size is 143 nm. High-resolution spherical aberration electron microscopy observed the unique honeycomb atomic arrangement pattern and exposed zigzag edges of 2H-phase MoTe2 nanosheets.
Catalytic performance
In an oxygen-saturated 0.5 M H2SO4 electrolyte, after MoTe2 nanosheets and graphene nanosheets are composited, they exhibit a relatively positive biasing potential (0.56 V vs. RHE) and outstanding H2O2 selectivity (up to 93%) ), its mass activity (27 A g-1at 0.4 V) is also second only to the best Pt-Hg and Pd-Hg alloys in the literature, and higher than Au-based alloys and N-doped carbon materials.
Comparison of the mass activity of MoTe2 nanosheets with Pt/Pd-Hg alloy and Au-based alloy
In addition, accelerated aging test experiments showed that after 5000 cycles, the activity and selectivity of MoTe2 nanosheets did not significantly decay; there was only a slight activity decay after overnight aging, but no obvious selective decay. Experiments have proved that MoTe2 nanosheets have good catalytic stability.
Principles of Catalysis
Theoretical calculations indicate that the suitable adsorption energy of the zigzag edge of the MoTe2 nanosheets on the reaction intermediate HOO* ensures excellent 2e-ORR catalytic activity, while the weaker adsorption energy for O* is not conducive to the deep reduction of O*, ensuring High selectivity for H2O2. The two-dimensional heat map drawn from the adsorption energy data of various materials on key reaction intermediates shows that PtHg4 has the best activity and selectivity, followed by MoTe2 nanosheets, while MoS2, MoSe2 nanosheets and Pt/C, etc. are far away from the highly active and selective region of 2e-ORR.

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