Enhanced Hydrogen Evolution Rate Using Piezoelectric K1/2Na1/2NbO3 Nanosheets by Controlling Annealing Temperature

Recently, novel catalytic technologies for the efficient production of H 2 have attracted considerable research attention. Piezocatalysis is one of the most efficient methods for using mechanical energy in nature to generate hydrogen. In this investigation, we fabricated KNN nanosheets (NSs) using a hydrothermal method and annealed the KNN NSs at various temperatures to manipulate the piezoelectric properties and oxygen vacancy in the material. The PFM measurements indicate that KNN-900 NSs have the largest piezoelectric coefficients d 33 of 11.13 pm/V. The results indicate that increasing the annealing temperature can significantly enhance the piezoelectric properties of the KNN NS materials. In contrast, X-ray photoelectron spectroscopy (XPS) spectra revealed that KNN-700 presented more enriched oxygen vacancies. Under dark conditions, KNN-800 had a hydrogen evolution rate of 1012.3 μmol g -1 h -1 ; this value represented a 23.3% and 107.5% enhancement with respect to those of KNN-900 and KNN-700, respectively. In addition, the results from the carbon dioxide reduction experiments demonstrated the excellent performance of KNN-800, with a CO production rate of 102.3 μmol g -1 h -1 . This investigation demonstrated that both the piezopotential and oxygen vacancies in piezoelectric materials play critical roles in the hydrogen generation process. This research not only investigates a lead-free ceramic nanomaterial for highly efficient hydrogen generation but also paves the way for utilizing annealing temperature to control the material’s piezoelectric properties and oxygen vacancies, thereby enhancing the efficiency of the piezocatalytic method for hydrogen production.