Efficient Production of Solar Hydrogen Peroxide Using Piezoelectric Polarization and Photoinduced Charge Transfer of Nanopiezoelectrics Sensitized by Carbon Quantum Dots.

Piezoelectric semiconductors have emerged as redox catalysts, and challenges include effective conversion of mechanical energy to piezoelectric polarization and achieving high catalytic activity. The catalytic activity can be enhanced by simultaneous irradiation of ultrasound and light, but the existing piezoelectric semiconductors have trouble absorbing visible light. A piezoelectric catalyst is designed and tested for the generation of hydrogen peroxide (H 2 O 2 ). It is based on Nb-doped tetragonal BaTiO 3 (BaTiO 3 :Nb) and is sensitized by carbon quantum dots (CDs). The photosensitizer injects electrons into the conduction band of the semiconductor, while the piezoelectric polarization directed electrons to the semiconductor surface, allowing for a high-rate generation of H 2 O 2 . The piezoelectric polarization field restricts the recombination of photoinduced electron-hole pairs. A production rate of 1360 µmol g catalyst -1  h -1  of H 2 O 2  is achieved under visible light and ultrasound co-irradiation. Individual piezo- and photocatalysis yielded lower production rates. Furthermore, the CDs enhance the piezocatalytic activity of the BaTiO 3 :Nb. It is noted that moderating the piezoelectricity of BaTiO 3 :Nb via microstructure modulation influences the piezophotocatalytic activity. This work shows a new methodology for synthesizing H 2 O 2  by using visible light and mechanical energy.