Although technological advancement is directly responsible for improving the quality of human life, it is characterized by overexploitation of natural resources, excessive consumption of energy and improper waste management that have resulted in significant degradation of the environment. The uncontrolled industrial wastewater discharge has disrupted the natural ecology contributing to severe health problems. Additionally, the excessive exploitation and consumption of fossil fuels contribute to excessive emissions of greenhouse gases, exacerbating climate change and global warming. Different solutions, including the adoption of clean energy alternatives, water splitting technologies and waste/pollution management remedies, have been extensively investigated to address this worrying situation.
Photocatalytic and electrocatalytic water splitting are promising strategies for decomposing polluted dye and producing hydrogen gas. Unfortunately, the limitations of quantum conversion efficiency remain the biggest challenge in their applications. Different techniques involving cocatalysts, heterostructure composites, surface defects and metal/non-metal doping have been extensively researched to enhance the photoelectrochemical process efficiency. Lately, piezoelectric effects and related ferro- and piezoelectric materials that provide suitable piezocatalysis strategies through electrochemical reactions have drawn much research attention.
Interestingly, the conversion of mechanical force into chemical energy holds prospect applications in wastewater treatment, organic matter degradation and hydrogen production. To this end, numerous piezocatalysts have been developed from many ferroelectric materials and transition metal dichalcogenides owing to their structural ability to induce piezopotential and initiate electrochemical processes without an additional power supply. Thus, combining photocatalysts and piezoelectric effects is predicted to improve photocatalytic activity that could inspire efficient water sitting, among other potential applications.
Herein, Dr. Meng-Chin Lin, Dr. Sz-Nian Lai, Dr. Kim Tuyen Le and led by Professor Jyh Ming Wu from National Tsing Hua University, Taiwan, developed an innovative self-powered photoelectrochemical microsystem consisting of environmentally friendly single-crystal quartz microrods assembled with titanium oxide (TiO2) nanoparticles. The synthetic effects of the piezopotential sensitized photocatalytic process was investigated through hydrogen evolution reaction (HER) and organic dye degradation test. The piezoelectricity of the as-synthesized quartz was confirmed via piezoresponse force microscopy (PFM) and Raman spectra. The overall performance and degradation efficiency of the quartz/TiO2 composite was evaluated and discussed. The original research article is now published in the journal, Nano Energy.
The research team showed that the quartz microrods served as self-induced bias subjected to mechanical stress that could produce extra electric fields in the presence of the TiO2 nanoparticles. It not only accelerated the separation of photoexcited carriers but also suppressed their recombination, thereby facilitating efficacious catalytic reactions. The effects of the interfacial stress between the two materials played a critical role in improving the piezopotential of the system. The quartz/TiO2 exhibited superior degradation efficiency and a constant reaction rate of 0.0624 min-1, 0.0281 min-1 and 0.0011 min-1 under piezophotonic, photocatalysis and piezocatalysis, respectively. Moreover, an optimal hydrogen production of about 438.48 µmol.g-1.h-1 was achieved through the synergistic piezophototronic effects, representing a 225% increase compared with the pristine quartz.
In summary, TiO2 nanoparticles and highly crystalline quartz synthesized from recycled rice hucks were successfully deposited on quartz surfaces via a hydrothermal method to create a self-powered photoelectrochemical quartz/TiO2 microsystem. Besides piezoelectric polarization, the results of PFM measurements and Raman spectra revealed that the effects of the interfacial stress considerably contributed to improving the piezopotential, and were consistent with the theoretical results. Overall, the piezophototronic effect exhibited outstanding performance due to the effects of quartz/TiO2 composite. In a statement to Advances in Engineering, Professor Jyh Ming Wu, the lead and corresponding author said their work realized the coupling effects of photocatalysis and piezocatalysis and the resulting self-powered photoelectrochemical microsystem holds promising application in environmental remediation and renewable energy development.
Lin, M., Lai, S., Le, K., & Wu, J. (2022). Self-powered photoelectrochemical quartz/TiO2 microsystem through piezopotential sensitized photocatalytic process. Nano Energy, 91, 106640.