| Abstrakt: |
Perovskite-type LaTiO2N with a bandgap energy of 2.1 eV is a promising semiconductor for solar (sea)water splitting to produce renewable hydrogen. However, the synthesis of an oxynitride with low defect density to achieve strong charge separation for high solar-to-hydrogen energy conversion is still challenging. Herein, we report less-defective, two-dimensional (2D) LaTiO2N crystals prepared from layered perovskite BaLa4Ti4O15 and their highly improved photoelectrochemical (PEC) seawater-splitting activity at neutral pH. The (111)-type layered perovskite BaLa4Ti4O15 has structural similarity to LaTiO2N and excess Ba species with a strong basicity, thus guaranteeing complete and fast nitridation accompanied by suppressed Ti4+ reduction. The prepared oxynitride, capable of absorbing visible light up to 610 nm, was highly crystalline and less-defective in both bulk and surface states, which is favorable for efficient photoreactions. Oxynitrides were also prepared from other layered perovskite oxides, namely La2Ti2O7 and La4Ti3O12, for comparison. Photoanodes using LaTiO2N were fabricated by spin-coating and then employed for driving PEC seawater splitting including chloride oxidation at neutral pH. The less-defective LaTiO2N exhibited a photocurrent density of approximately 2.4 mA cm−2 at 1.23 VRHE (4.9 mA cm−2 at 1.36 VRHE) in 0.5 M NaCl electrolyte at pH 6.4 under AM 1.5G simulated sunlight, indicating hitherto unreported remarkable activity. This work presents the first demonstration of the complete conversion of layered perovskite BaLa4Ti4O15 into perovskite LaTiO2N as well as the types of starting oxides that reduce the defect density of the resulting oxynitride, thereby improving the hydrogen evolution rate at neutral pH. [ABSTRACT FROM AUTHOR] |
