SnFe₂O₄/ZnIn₂S₄/PVDF piezophotocatalyst with improved photocatalytic hydrogen production by synergetic effects of heterojunction and piezoelectricity

The polarized electric field inside piezoelectric materials has been proven to be a promising technique to boost photogenerated charge separation. Herein, a novel flexible SnFe2O4/ZnIn2S4/polyvinylidene fluoride ((CH2CF2)n, PVDF) (P–SZ) film piezophotocatalyst was successfully synthesized by combining PVDF, an organic piezoelectric material, with a SnFe2O4/ZnIn2S4 (SFO/ZIS) type II heterojunction photocatalyst. The hydrogen evolution rate of SFO/ZIS heterojunction with a SFO content of 5% is about 846.79 μmol·h−1·g−1, which is 3.6 times that of pristine ZIS. Furthermore, after being combined with PVDF, the optimum hydrogen evolution rate of P–SZ is about 1652.7 μmol·h−1·g−1 in the presence of ultrasound, which exceeds that of 5% SFO/ZIS by an approximate factor of 2.0. Based on experimental results, the mechanism of the improved photocatalytic performance of P–SZ was proposed on the basis of the piezoelectric field in PVDF and the formed heterojunction between SFO and ZIS, which effectively boosted the separation of photoinduced charges. This work provides an efficient strategy for multi-path collection and utilization of natural solar and vibrational energy to enhance photoactivity.</p

Effect of Organic Sulfur Compounds in the Precursor on the Capacitance Performance of Prepared Activated Carbon

Activated carbons (ACs) were prepared with pitch as an analogous precursor in the presence of dibenzothiophene (DBT) and were applied as supercapacitor electrode materials. KOH was employed in the activation. The influence of DBT content in the precursor on the pore structure of the resultant AC and its capacitive performance were investigated intensively. The results show that DBT in the precursor can react with the KOH activation agent, thus reducing the actual KOH/char ratio. It is found that the presence of DBT in the precursor not only reduces the pore volume and the specific surface area of the resultant AC but also deteriorates the capacitance and rate capability of the AC electrode. However, of special interest is the fact that no residual sulfur was found in the prepared AC regardless of the DBT content in the precursor