Piezo-Activated Metal-Free Donor-Acceptor Photocatalytic Overall Water Splitting System Toward Highly-Efficient...

The potential mismatch of band structures to water redox potentials for most of photocatalysts restricts the development of photocatalytic overall water splitting (OWS). Herein, a well-defined donor-acceptor polymer model photocatalyst (HFPTP-Bpy-Hz), featuring an unsuitable band structure for OWS, was designed. It was demonstrated that the OWS ability of HFPTP-Bpy-Hz for H₂ and H₂O₂ generation was activated by the bending of its unmatched conduction band in the piezo-induced built-in electric field, as well as the thermodynamically favorable two-electron pathway for H₂O₂-evolved water oxidation on bipyridine structure. HFPTP-Bpy-Hz showed excellent metal-free photo/piezo-catalytic OWS performance for H₂ and H₂O₂ generation (1795 and 1571 µmol·g^-1·h^-1, respectively) better than the performances in literatures. Effective separation of photo-generated carriers achieved by piezo-induced built-in electric field and hydrazone bond-based electron transfer channel, and low energy barriers of water splitting in the presence of hydrazone bond linkage, collectively contributed to the outstanding photo/piezo-catalytic OWS performance of HFPTP-Bpy-Hz. Furthermore, the hydrazone bond-based positive correlation between the polarity of the polymer backbone and piezo/photocatalytic activity at the molecular level was clearly demonstrated through targeted regulation of connecting bonds and building blocks. This work offers valuable insights for constructing the promising solar light-driven OWS systems using photocatalysts with unsuitable band structures.