Defect modulation usually has a great influence on the electronic structures and activities of photocatalysts. Here, atomically layered g-C 3 N 4 modified via defect engineering with nitrogen vacancy and cyanogen groups is obtained through two facile steps of thermal treatment (denoted as A-V-g-C 3 N 4 ). Detailed analysis reveals that the atomic-layered graphitic carbon nitride (2.3 nm) with defect engineering modifying provides more active sites and decreases the electron/hole transferring distances. More importantly, the defects that contain nitrogen vacancies and cyanogen groups extend the responsive wavelength to 650 nm, which effectively suppresses the quantum size effect of atomic-layered g-C 3 N 4 . Therefore, the as-obtained A-V-g-C 3 N 4 exhibited a photocatalytic H 2 evolution rate and apparent quantum yield of 3.7 mmol•g −1 •h −1 and 14.98% (λ > 420 nm), respectively. This work is expected to provide guidance for the rational design of atomic-layered g-C 3 N 4 . KEYWORDS: g-C 3 N 4 , defects engineering, atomic layered g-C 3 N 4 , quantum size effect, H 2 evolution
The
Co
3
O
4
@CdS double-layered hollow spheres
were first prepared by the template-removal method with the assistance
of the ZIF-67 material; the structure has been proved by transmission
electron microscopy (TEM). The Co
3
O
4
@CdS hollow
spheres calcinated at 400 °C exhibited the highest photodegradation
activity. Nearly 90% phenol was degraded after 2 h of visible-light
irradiation. More than 80% rhodamine-B (RhB) was degraded within the
first 30 min and nearly eliminated after 1 h of irradiation. The mechanism
of the photodegradation reaction was investigated. Based on the analysis
of electron spin resonance (ESR) spectra and radical trapping test,
it was found that superoxide radicals are the major oxidative species
for dye degradation and holes and hydroxyl radicals are the major
oxidative species for phenol degradation. These results may be used
in industrial wastewater treatment. The reaction obeys first-order
reaction kinetics, and the rate constant of the Co
3
O
4
@CdS hollow sphere in dye degradation is 0.05 min
–1
and that in phenol degradation is 0.02 min
–1
,
which is three times higher than that of CdS nanoparticles. These
results indicated the high oxidizing ability of the samples.
It is a great challenge to simultaneously improve the visible light absorption capacity and enhance photon-generated carrier separation efficiency of photocatalysts.
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