Constructing magnetically propelled piezoelectric and pyroelectric bifunctional micromotors to boost the photocatalytic H2 production involving biomass reforming

Abstract

Biomass-assisted photocatalytic water splitting for hydrogen (H₂) production has attracted widespread interest, which is important for the development of green H₂ energy and the high value-added utilization of biomass. Although photothermal utilization can improve solar energy conversion efficiency, the elevated temperature also enhances the likelihood of electron-hole collisions. Herein, magnetically propelled PVDF/Fe₃O₄@g-C₃N₄ spiral micromotors were constructed to easily foster the synergistic coupling of piezoelectric and pyroelectric effects, which is beneficial to enhance the directional migration of photogenerated carriers at high temperatures. With both piezo- and pyroelectric effects, the biomass glucose involved H₂ production rate on PVDF/Fe₃O₄@g-C₃N₄ spiral micromotors is 42.3 μmol/h, representing a significant increase of 31.9 times compared to water splitting without these effects, and the average apparent quantum yield at ordinary pressure can reach 12.6 %. Furthermore, photoluminescence and variable-temperature electrochemistry demonstrate that the piezo-pyroelectric coupling can accelerate the separation of carriers. Meanwhile, COMSOL simulations and KPFM tests show that the built-in electric field of the sample is enhanced under the piezo-pyroelectric effect. The spiral micromotors can easily realize the synergism of piezoelectric and pyroelectric effects, which provides an effective strategy to enhance the built-in electric field and thereby improve the performance of photocatalytic H₂ evolution involving biomass reforming.