Nitrogen-doped
carbon-wrapped C,N-codoped TiO2 (CN@C,N-TiO2) was successfully prepared using a facile and efficient method
involving hydrolysis and calcination under Ar using tetrabutyl titanate
and 2,6-diaminopyridine as the precursors. X-ray photoelectron spectroscopy
(XPS) and valence band XPS measurements reveal the successful codoping
of interstitial carbon and nitrogen into TiO2, which leads
to a visible-light absorption of up to ∼550 nm in the UV–vis
diffuse reflectance spectra. Raman spectra and high-resolution transmission
electron microscopy results show that N-doped carbon exists on the
surface of C,N-TiO2, which gives rise to the efficient
separation of photoexcited charge carriers, as determined by photoluminescence
and electrochemical impedance spectroscopy. Benefiting from the combined
effects of a surface-coated N-doped carbon layer and C,N-codoping,
the photocatalyst calcined at 450 °C exhibits remarkable visible-light
activity toward the hydrogen evolution reaction in the water splitting
process with a H2 production rate of 833.2 μmol h–1 g–1 under 94 mW cm–2 visible-light illumination (λ > 420 nm). Moreover, the
representative
CN@C,N-TiO2 sample can maintain its activity for at least
40 h.
The
exploration of low-cost, high-performance, and stable photocatalysts
for the highly efficient conversion and storage of solar energy in
hydrogen is of great importance. This study presents a novel pyridine-type
carbonitrides (CN)-modified surface-disordered C-doped TiO2 (PCN/CTiO2@TiO2–x
)
catalyst used for photocatalytic H2 evolution from water.
The employed preparation method of hydrolysis–calcination has
the advantages of low-cost raw materials and easy scale-up. The optimized
PCN/CTiO2@TiO2–x
exhibited
an impressive hydrogen evolution rate of ∼3743 μmol h–1 g–1 under simulated solar light
(AM 1.5) and remained stable after five cycles. The maximal quantum
efficiency reached 37.5% at 370 nm and 7.0% at 400 nm, which was superior
or comparable to several reported relevant TiO2-based catalysts.
Benefiting from the pyridine-type CN modification, disordered surface
layer (TiO2–x
), and increased oxygen
vacancies/Ti3+ species, the photogenerated electrons moved
rapidly from the visible-response C-doped TiO2 to CN to
participate in the photoreduction reaction, which led to a marked
improvement in the catalytic activity.
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