Effect of Controlled Oxygen Vacancy on H2-Production through the Piezocatalysis and Piezophototronics of Ferroelectric R3C ZnSnO3 Nanowires

This study is the first to demonstrate that ferroelectric R3c LiNbO3-type ZnSnO3 nanowires (NWs), through the piezocatalysis and piezophototronic process, demonstrate a highly efficient hydrogen evolution reaction (HER). The polarization and electric field curves indicate that ZnSnO3 NWs exhibit typical ferroelectric hysteresis loops. Time-resolved photoluminescence spectra reveal that the relaxation time increases with the increasing concentration of oxygen vacancies. Moderated 3H-ZnSnO3 NWs (thermally annealed for 3 h in a hydrogen environment) have the longest extended carrier lifetime of approximately 8.3 ns. The piezoelectricity-induced HER, via the piezocatalysis process (without light irradiation), reaches an optimal H-2-production rate of approximately 3453.1 mu mol g(-1) h(-1). Through the synergistic piezophototronic process, the HER reaches approximately 6000 mu mol g(-1) in 7 h. Crucially, the mechanical force-induced spontaneous polarization functions as a carrier separator, driving the electron and hole in opposite directions in ferroelectric ZnSnO3 NWs; this separation reduces the recombination rate, enhancing the redox process. This theoretical analysis indicates that the photocatalytic and piezocatalytic effects can synergistically enhance piezophototronic performance through capitalizing on well-modulated oxygen vacancies in ferroelectric semiconductors. This study demonstrates the essential role of this synergy in purifying water pollutants and converting water into hydrogen gas through the piezophototronic process.