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

Abstract

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 (H2O2). It is based on Nb‐doped tetragonal BaTiO3 (BaTiO3: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 H2O2. The piezoelectric polarization field restricts the recombination of photoinduced electron–hole pairs. A production rate of 1360 µmol gcatalyst−1 h−1 of H2O2 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 BaTiO3:Nb. It is noted that moderating the piezoelectricity of BaTiO3:Nb via microstructure modulation influences the piezophotocatalytic activity. This work shows a new methodology for synthesizing H2O2 by using visible light and mechanical energy.

Effective modification of photocatalytic and piezocatalytic performances for poly(heptazine imide) by carbon dots decoration

“…3c, indicating the promoted transfer of photogenerated electron-hole pairs. 40 PHI/CDots-25 has a smaller radius in the electrochemical impedance spectroscopy (EIS) Nyquist plots compared with PHI (Fig. 3d), reflecting the better transport and lower transfer resistance of charge carriers by CDots decoration.…”

“…3d), reflecting the better transport and lower transfer resistance of charge carriers by CDots decoration. 40,42 Evaluation of photocatalytic and piezocatalytic activities…”

“…As reported, the polarized charge transfer is important for piezocatalysis, and the facilitation of free charge transfer can promote piezocatalytic performances. 40 It is assumed that the promoted separation, the smoother transfer, and utilization of charge carriers in PHI/ CDots also play important roles in the piezocatalytic processes and thus increase the efficiency of the piezocatalytic reactions.…”

“…37 Previously, CDots decoration has shown great potential in improving the photocatalysis and ( photo-)piezocatalysis performances, working as photosensitizers, charge carrier transfer promoters or catalysts. [36][37][38][39][40] For example, the CDots decorated melon structure C 3 N 4 showed benchmark overall water splitting activities (solar-to-hydrogen efficiency of 2.0%, robust stability in 200 runs). In the C 3 N 4 /CDots composite, CDots contributed to the improved visible light absorption and catalyzed the two-step reaction for O 2 evolution.…”

“…38 Besides, it was reported that the ( photo-)piezocatalytic H 2 O 2 generation performances of BaTiO 3 :Nb (Nb-doped tetragonal BaTiO 3 ) can be significantly improved by the modification of carbon quantum dots, which not only worked as the sensitizer but also promoted the charge transfer on the surface. 40 More attempts on the CDots modified photocatalysts and piezocatalysts are widely desirable.…”