β-CuGaO2: a ferroelectric semiconductor with narrow band gap as degradation catalyst for wastewater environmental remediation

As a narrow band gap semiconductor, wurtzite β-CuGaO2 has drawn increasing attention in the area of solar energy. Although β-CuGaO2 has been theoretically predicted to possess ferroelectric polarization, its experimental ferroelectric characterization and practical applications have not yet been presented. Herein, firstly we experimentally confirmed its ferroelectric property via hysteresis loop measurement. The result showed a remanent polarization value of 10.20 μC·cm−2 with low coercive electric field of 6.45 kV·cm−1 at 20 Hz at room temperature, while the leakage current density (J) value was found to be 1.188 A·cm−2, which suggested the property of a larger remnant polarization with low coercive electric field than current value if the compactness was strengthened. Then, the synergistic effect of ferroelectric and semiconductor was comparatively highlighted by the experiment of pollutant degradation. Within 30 min, methyl orange degradation efficiency had reached 30.73% only in the case of spontaneous polarization (electricity), while it could reach 67.58% under the effect of pre-polarized β-CuGaO2 powder due to the modulating orientation of ferroelectric domains. Once irradiated (light), it was up to 92% within 30 min; in comparison, it merely took 16 min up to 92% degradation efficiency under both illumination and pre-polarization. If without illumination, it was 92.01% with 30 min in the condition of ordinary ultrasonic vibration (force) while under both illumination and ultrasonic vibration, only 11 min was spent to reach 92.79% degradation efficiency. All these results felicitously indicated that β-CuGaO2 had fascinating potential in energy harvesting (such as electricity, light, force) and transformation as wastewater environment remediation catalyst.