Acceleration of the electron transfer for efficient photocatalytic hydrogen evolution via regulating the surfactant around the active center in 2D MOFs

Although surfactants have been proved to be effective in controlling the size and morphology to prepare high-quality two-dimensional (2D) MOF nanosheets, the impact of surfactants remaining on the 2D MOF nanosheets on their microenvironment is rarely reported. In this paper, polyvinylpyrrolidone (PVP) was used as surfactant to synthesize Co-TCPP(Pd) (abbreviated as Co-Pd) nanosheets, and the content of PVP attached to Co-Pd nanosheets was controlled by ethanol treatment, to regulate the microenvironment around Co-Pd nanosheets. The XRD, FT-IR, XPS, TEM, and TG were used to confirm that after ethanol ultrasonic treatment, the PVP content on Co-Pd nanosheets was gradually reduced without damaging the original structure and morphology of Co-Pd nanosheets. PVP attached to Co-Pd nanosheets will slow down the electron migration rate, affecting the microenvironment around co-catalyst Pd, which has been confirmed by EIS, PL and DFT etc. The results exhibited that the Co-Pd-6 obtained by ethanol ultrasonic treatment 6 times showed the more excellent photocatalytic hydrogen evolution activity (8284.25 umol·g-1·h-1), which was 4.02 times as that of Co-Pd-0 (2059.59 umol·g-1·h-1) without ethanol ultrasonic treatment), indicating that PVP will have a negative impact on the microenvironment around the co-catalyst, thereby affecting the photocatalytic hydrogen evolution performance. This study indicates that efficient photocatalytic hydrogen evolution can be achieved via adjusting the microenvironment around the co-catalyst to promote electron transfer.