Efficient solar-driven water oxidation using particulate perovskite oxynitrides by defect engineering

以钙钛矿型BaTaO2N为原料，进行了高效太阳能水氧化研究。利用层状钙钛矿富钡Ba5Ta4O15成功制备了BaTaO2N，在1223 K的NH3流下进行30 h的高温氮化过程中抑制了表面缺陷，如Ta4+和/或Ta3+的还原性。随后，在Ar流中对氮化产物进行退火处理，以减少额外的氧杂质和/或氮空位，从而减少太阳水氧化过程中光生电荷的重组。通过x射线光电子能谱和氧氮燃烧分析，分别测定了BaTaO2N颗粒上与Ta和O/N有关的缺陷密度的降低。这些方法在抑制BaTaO2N表面缺陷和杂质方面非常有效。因此，在颗粒状BaTaO2N光阳极上进行光电化学水分解时，产生了1.23 VRHE （6.5 mA cm-2）的光电流密度，驱动实际阳极光电流的起始电位更负地移动到0.6 VRHE，从而提供了1.4%的半电池太阳能-氢能量转换效率。这是钙钛矿型AB(O，N)3光阳极的新记录。

The Perovskite-type BaTaO2N had been studied as a starting material for this research based on efficient solar water oxidation. BaTaO2N was successfully prepared from layered perovskite, Ba-rich Ba5Ta4O15 to suppress surface defects such as reduced species of Ta4+ and/or Ta3+ during the high temperature nitridation under NH3 flow at 1223 K for 30 h. Subsequently, the annealing treatment of the nitrided product in an Ar flow was performed to reduce additional oxygen impurities and/or nitrogen vacancy and thus to decrease the recombination of photogenerated charges during the solar water oxidation.The decreased defect densities related to Ta and O/N species on the BaTaO2N particles were determined by X-ray photoelectron spectroscopy and oxygen-nitrogen combustion analysis, respectively. These approaches were very effective at suppressing the surface defects and impurities on BaTaO2N. Consequently, the photocurrent density at 1.23 VRHE of 6.5 mA cm-2 was generated during the photoelectrochemical water splitting over a particulate BaTaO2N photoanode and the onset potential driving actual anodic photocurrent was shifted more negatively to 0.6 VRHE, providing a half-cell solar-to-hydrogen energy conversion efficiency of 1.4%. This is a new record for a photoanode based on perovskite-type AB(O,N)3.