Piezoelectric polarization coupled with photoinduced catalytic oxidation technology for environmental pollution control: Recent advances and future prospects.

Energy scarcity and environmental pollution concerns have become substantial impediments to sustainable global economic development. The advent of semiconductor photocatalysis technology provides a potential possibility for effectively alleviating excessive energy consumption and maintaining the long-term stability of the aqueous ecosystem. However, the inefficient transmission efficiency of charge carriers and the high recombination rate of photogenerated electron-hole pairs will culminate in the mediocre catalytic performance observed in conventional semiconductor materials. Fortunately, the piezo-photocatalysis ingeniously integrates the piezoelectric properties of piezoelectric crystals with the optoelectronic properties of semiconductors, thus building a theoretical system of photo-electric-chemical three-phase coupled catalysis. Currently, the photo-mechanical energy synergistic catalytic oxidation degradation process, as a cutting-edge technology based on clean renewable energy, has been perceived as a promising environmental remediation strategy. Herein, a critical review of the application of piezo-photocatalysis in environmental pollution control was delivered. We undertook a comprehensive analysis to elucidate the underlying enhancement mechanism of the piezoelectric effect on photocatalysis in terms of charge migration dynamics and pertinent energy band bending phenomena. In addition, we meticulously summarized diverse innovative methods for introducing vibration energy in piezo-photocatalytic degradation systems (ultrasound, fluid mechanical energy, airflow, self-assembled reactors, etc.). Then, state-of-the-art research advances in the field of environmental pollution control and the corresponding environmental decontamination mechanisms were elaborated based on various integration modes of catalysts (single component, noble metal deposition, heterojunction, coupled substrate materials, etc.). Eventually, an in-depth assessment of current limitations and development trends of piezo-photocatalytic degradation technology has been proposed, along with proactive strategies aimed at surmounting the existing challenges.

Brand equity and the Covid-19 stock market crash: Evidence from U.S. listed firms.

Brand equity has played an important role in firms' stock performance, especially during the stock market crash provoked by Covid-19. Our manuscript investigates how brand equity impacts stock performance during the Covid-19 crash. Firms with top brands should be a particularly attractive "safe harbor" in the crash to investors since consumer loyalty and demand advantages brought by brand equity enable firms to retain stable cash flows and mitigate the macroeconomic shock. Based on U.S. listed firms, we find that firms with top brands experience higher stock returns, lower systematic risk and lower idiosyncratic risk in the Covid-19 crash than other firms. Moreover, our findings are used to distinguish the brand equity effect from the corporate social responsibility (CSR) effect on stock performance during the Covid-19 crash.