Construction of microbial piezo/photo system for nitrate conversion to ammonium driven by the synergistic effect of hydraulic kinetic and light energy.

Integrating photocatalytic materials with electroactive microorganisms presents a promising route for solar energy-driven bioconversion, but is limited by low efficiency and high charge transfer barriers. Herein, dual-functional Bi2WO6 nanosheets (as piezo/photocatalytic materials) capable of harvesting both hydraulic kinetic and light energy from the natural environment were combined with an electroactive bacterium of Shewanella oneidensis MR-1 for constructing the Shewanella oneidensis MR-1/Bi2WO6 biohybrid system. This system was able to enhance the charge transfer efficiency and modulate the energy band structure, thereby efficiently reducing NO3- to NH4+ with a reduction efficiency as high as 93.4%. The NH4+ production rate (62.2 µmol·L-1·h-1) and selectivity (96.9%) were approximately 30% higher than that driven by the sole hydraulic kinetic energy and significantly superior to that driven by the sole light energy, indicating a synergistic effect between the piezoelectric and photoelectric fields. Transient piezo-photocurrent (TPC) tests, kelvin probe force microscopy (KPFM) measurements, density functional theory (DFT) calculations and quantitative real-time polymerase chain reaction (real-time PCR) collectively confirmed that the piezoelectric polarization field generated from Bi2WO6 nanosheets can not only improve the carrier separation efficiency, allowing more piezo/photo-electrons to transfer to the surface of S. oneidensis MR-1, but also overcome the interfacial charge transfer barrier, facilitating the uptake of piezo/photo-electrons by S. oneidensis MR-1 to achieve NO3- reduction to NH4+. This work provides new insights into efficient biomanufacturing and waste conversion driven by multiple energy sources.