Sensitization of bismuth tungstate with magnesium phthalocyanine for photoinduced charge redistribution and electron localization: CO2 photoreduction from the vis to NIR region

Abstract

Spectral sensitization of 2D ultrathin bismuth tungstate (Bi₂WO₆) nanosheets with magnesium phthalocyanine (MgPc) molecules was performed to extend the light absorption ability to the NIR region. The optimal loading of MgPc on Bi₂WO₆ demonstrated a 2.2-fold improvement in CH₄ yield as compared to that of bare Bi₂WO₆ from CO₂ photoreduction under visible light illumination (λ > 410 nm). The developed sample exhibited remarkable stability, maintaining 96.3% of reactivity after three consecutive cycles. This improved photocatalytic performance can be attributed to better solar light utilization and enhanced charge separation. Photoactivity was also observed even under low-photonic NIR light. DFT calculations were performed to provide qualitative insights into the charge transfer process, divulging that the incorporation of MgPc promotes electron localization at the O atom and therefore enhances CO₂ reduction activity. The experimental results and theoretical calculations disclosed the crucial role of MgPc in facilitating electron excitation in the NIR region to further drive the photocatalytic activity of Bi₂WO₆. In brief, this work provides useful insights into designing an efficient 2D photocatalyst for solar energy-driven fuel production from CO₂.