Improved visible-light activities of ultrathin CoPc/g-C3N4 heterojunctions by N-doped graphene modulation for selective benzyl alcohol oxidation

The interface modulation is the key factor affecting the photoactivity of metal phthalocyanine (MPc)/gC3N4 heterojunctions for aerobic selective alcohol oxidation. Here, we have successfully fabricated the Ndoped graphene-modulated CoPc/g-C3N4 nanosheets (CoPc/NG/CN) heterojunctions. Optimal CoPc/NG/ CN photocatalyst demonstrates approximately fourfold photoactivity improvement for benzyl alcohol oxidation with ~99% selectivity toward benzyl aldehyde and of approximately ninefold 2,4dichlorophenol degradation rate compared with bare CN, using O2 as oxidant. By means of steadystate surface photovoltage responses in N2 atmosphere, time-resolved photoluminescence spectra, single-wavelength photocurrent action spectra, and electrochemical O2 reduction measurements, it is confirmed that the exceptional photoactivities of resulting CoPc/NG/CN heterojunction are attributed to the facilitated interfacial charge transfer between CoPc and CN by the modulation of NG with favorable electron-induced capacity. In addition, more enriched hydroxyl groups of NG by N doping could induce high dispersion of CoPc molecules via H-bonding effect, resulting in the increase of exposed number of CoPc as visible-light absorption units and single Co2 thorn sites as catalytic centers for O2 activation so as to further benefit the photocatalytic oxidation processes. This work provides a feasible interfacial modulation strategy to fabricate efficient supported MPc-based heterojunction photocatalyst nanomaterials. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Interface modulation plays a key role in the photoactivity of metal phthalocyanine/g-C3N4 heterojunctions. In this study, Ndoped graphene-modulated CoPc/g-C3N4 nanosheets were successfully fabricated. The optimized heterojunction photocatalyst exhibited significantly improved activity due to the facilitated interfacial charge transfer and increased visible-light absorption and catalytic centers.