Herein we demonstrate that adding single-atoms of selected transition metals to graphitic carbon nitrides allow the tailoring of their electronic and chemical properties of these 2D nanomaterials, directly impacting their...
Photocatalysis provides a sustainable pathway to produce
the consumer
chemical H2O2 from atmospheric O2 via an oxygen reduction reaction (ORR). Such an alternative is attractive
to replace the cumbersome traditional anthraquinone method for H2O2 synthesis on a large scale. Carbon nitrides
have shown very interesting results as heterogeneous photocatalysts
in ORR because their covalent two-dimensional (2D) structure is believed
to increase selectivity toward the two-electron process. However,
an efficient and scalable application of carbon nitrides for this
reaction is far from being achieved. Poly(heptazine imides) (PHIs)
are a more powerful subgroup of carbon nitrides whose structure provides
high crystallinity and a scaffold to host transition-metal single
atoms. Herein, we show that PHIs functionalized with sodium and the
recently reported fully protonated PHI exhibit high activity in two-electron
ORR under visible light. The latter converted O2 to up
to 1556 mmol L–1 h–1 g–1 H2O2 under 410 nm irradiation using inexpensive
but otherwise chemically demanding glycerin as a sacrificial electron
donor. We also prove that functionalization with transition metals
is not beneficial for H2O2 synthesis, as the
metal also catalyzes its decomposition. Transient photoluminescence
spectroscopy suggests that H-PHIs exhibit higher activity due to their
longer excited-state lifetime. Overall, this work highlights the high
photocatalytic activity of the rarely examined fully protonated PHI
and represents a step forward in the application of inexpensive covalent
materials for photocatalytic H2O2 synthesis.
Here we report a photocatalytic system based on crystalline carbon nitrides (PHI) and highly dispersed transition metals (Fe, Co and Cu) for controlled methane photooxidation to methanol under mild conditions....
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