The direct oxidation of benzene to phenol with H2 O2 as the oxidizer, which is regarded as an environmentally friendly process, can be efficiently catalyzed by carbon catalysts. However, the detailed roles of carbon catalysts, especially what is the active site, are still a topic of debate controversy. Herein, we present a fundamental consideration of possible mechanisms for this oxidation reaction by using small molecular model catalysts, Raman spectra, static secondary ion mass spectroscopy (SIMS), DFT calculations, quasi in situ ATR-IR and UV spectra. Our study indicates that the defects, being favorable for the formation of active oxygen species, are the active sites for this oxidation reaction. Furthermore, one type of active defect, namely the armchair configuration defect was successfully identified.
Despite the rocketing
rise in power conversion efficiencies (PCEs), the performance of perovskite
solar cells (PSCs) is still limited by the carrier transfer loss at
the interface between perovskite (PVSK) absorbers and charge transporting
layers. Here, we propose a novel in situ passivation strategy by using
[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) to improve
the charge dynamics at the rear PVSK/CTL interface in the n-i-p structure
device. A pre-deposited PCBM-doped PbI2 layer is redissolved
during PVSK deposition in our routine, establishing a bottom-up PCBM
gradient that is facile for charge extraction. Meanwhile, the surface
defects are in situ-passivated via PCBM–PVSK interaction, which
substantially suppresses the trap-assisted recombination at the rear
interface. Due to the synergistic effect of charge-extraction promotion
and trap passivation, the fabricated PSCs deliver a champion PCE of
20.10% with attenuated hysteresis and improved long-term stability,
much higher than the 18.39% of the reference devices. Our work demonstrates
a promising interfacial engineering strategy for further improving
the performance of PSCs.
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