Design and fabrication of semiconductor
based composite photocatalysts
with matching band structure is an important strategy to improve charge
separation of photogenerated electron–hole pairs for photocatalytic
hydrogen production. In our study, by aid of the simple and cost-effective
molten salts method, a series of phase-controlled and composition-tuned
calcium tantalate composite photocatalysts has been prepared by adjusting
the initial atomic ratio of Ta/Ca precursors. We demonstrate the strong
correlation between the photocatalytic activities of calcium tantalate
composite photocatalysts for hydrogen evolution and respective phase
compositions. Without any cocatalysts, these composites with the optimized
phase composition of cubic α-CaTa2O6/hexagonal
Ca2Ta2O7, cubic CaTa2O6/hexagonal Ca2Ta2O7/orthorhombic
β-CaTa2O6, or cubic α-CaTa2O6/orthorhombic β-CaTa2O6 showed
very high photocatalytic H2 production activities in the
presence of methanol. It is attributed mainly to a significantly improved
photoexcited charge carrier separation via the junctions and interfaces
in the composites. Further by in situ photodeposition of noble metal
nanoparticles (Pt or Rh) as cocatalysts the photocatalytic activity
of these composites was greatly promoted for H2 production.
The study on convenient fabrication of phase-coexisting composite
photocatalysts with matching band structure for improving the photocatalytic
hydrogen production sheds light on developing efficient composite
photocatalyst as a means for conversion of solar energy to chemical
energy.
Nickel–iron‐based layered double hydroxides (NiFe LDHs) have attracted tremendous research and industrial interests for oxygen evolution reaction (OER) electrocatalysis. However, methodologies on simultaneous regulation of performance‐influencing factors remain scarce and their real synergistic effects are not clear enough. Herein, a versatile polyoxometallic acids (POMs) etching approach is reported to ingeniously reconstruct NiFe LDH, including 3D morphological nanotailoring, Fe3+ and α‐Ni(OH)2 active species reconfiguration, creation of multiple Ni, Fe, and O vacancies, and intercalation of POM polyanionic clusters. The experimental and theoretical data collaboratively unveil that control of the key performance‐influencing factors and their multiple synergistic mechanisms dominantly contribute to the step‐like OER performance enhancement. The reinforced electrocatalyst is further produced with low cost and high performance up to Ф180 mm in diameter, showing its feasibility and advancement of the promising configuration of NiFe LDH‐PMo12(+) II Ni@NiFe LDH(−) for alkaline anion‐exchange‐membrane electrode stack cells. Furthermore, to mathematically evaluate the evolution, a novel empirical formula is proposed for quantitative identification of structure–activity correlations, which offers an opportunity for first and fast reliability on materials screening.
The facile two-step preparation procedure of a novel magnetic nano-solid acid catalyst is described, which includes grafting an ionic liquid onto Fe 3 O 4 nanoparticles, followed by the sulfonation of phenyl groups in the ionic liquid. The catalytic performance of this novel material has been systematically studied in the acetal formation of benzaldehyde and ethylene glycol. The experimental results testify this catalyst possesses high catalytic activity with a yield of 97% under mild reaction conditions. Furthermore, the catalyst is readily separated using a permanent magnet and it is reusable without any significant decrease in catalytic activity.
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