Enhancing the internal electric field via twinning for boosting photocatalytic plastic reformation and H2 production†

Abstract

The sustainable conversion of plastic waste to reduce the environmental burden and recover valuable chemicals is of great significance. However, low charge separation efficiency and the rapid recombination of charge carriers hinder the activity of a photocatalyst. Herein, we report highly twinned ZnSe nanowires (T-ZnSe), which can construct a ‘micro-band’ slightly higher than the conduction band (CB) through the ingenious structure of zinc blende/wurtzite (ZB/WZ), thus forming an internal electric field (IEF) on the twin boundary, providing a strong driving force for the instantaneous separation of electrons and holes after generation. It was found that compared with single crystal ZnSe (S-ZnSe), the photocatalytic reforming of PLA by T-ZnSe produced H₂ and organic acids yields that were improved by 4.15 times and 4.27 times, respectively. In addition, the yield of H₂ and organic acids produced by the photocatalytic reforming of PET by T-ZnSe increased by 5.25 times and 4.80 times, respectively. The enhanced product output is mainly attributed to the enhanced IEF and rapid migration rate, which promote their effective charge separation. Density functional theory (DFT) calculations and photoelectric tests show that the IEF generated in the twin structure is enhanced by 3.76 times. The time-of-flight (TOF) mobility test further demonstrates that the carrier migration rate also doubled under a strong IEF. This study proves that the synergy between IEF and migration rate can promote the charge separation of photocatalysts and provides a new direction for future research on plastic modification using other photocatalysts.