Elucidating the impact of A-site cation change on photocatalytic H-2 and O-2 evolution activities of perovskite-type LnTaON(2) (Ln = La and Pr)

作者：Hojamberdiev Mirabbos; Bekheet Maged F; Hart Judy N; Vequizo Junie Jhon M; Yamakata Akira; Yubuta Kunio; Gurlo Aleksander; Hasegawa Masashi; Domen Kazunari; Teshima Katsuya

来源：Physical Chemistry Chemical Physics, 2017, 19(33): 22210-22220.

DOI：10.1039/c7cp03714g

Transition metal (oxy) nitrides with perovskite-type structures have been regarded as one of the promising classes of inorganic semiconductor materials that can be used in solar water splitting systems for the production of hydrogen as a renewable and storable energy carrier. The performance of transition metal (oxy) nitrides in solar water splitting is strongly influenced by the crystal structure-related dynamics of photogenerated charge carriers. Here, we have systematically assessed the influence of A-site cation exchange on the visible-light-induced photocatalytic H-2 and O-2 evolution activities, photoanodic response, and dynamics of photogenerated charge carriers of perovskite-type LnTaON(2) (Ln = La and Pr). The structural refinement results reveal the orthorhombic Imma and Pnma structures for LaTaON2 and PrTaON2, respectively; the latter has a more distorted crystal structure from the ideal cubic perovskite due to the smaller size of Pr3+ cations. Compared with LaTaON2, PrTaON2 exhibits lower photocatalytic H-2 and O-2 gas evolution activities and photoanodic response owing to an excessive amount of intrinsic defects associated with anionic vacancies and reduced tantalum species stemming from a long high-temperature nitridation process under reductive NH3 atmosphere. Transient absorption signals evidence the faster decay of photogenerated electrons (holes) in Pt (CoOx)-loaded LaTaON2 than that in Pt (CoOx)-loaded PrTaON2, consistent with the photocatalytic and photoelectrochemical performance of the two photocatalysts. This study suggests that in addition to selecting a suitable A-site cation, it is prerequisite to synthesize LnTaON(2) (Ln = La and Pr) crystals with a low defect density to improve their photo-conversion efficiency for solar water splitting.

• 出版日期2017-9-7