Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway.
Photochem Photobiol Sci. 2019 Apr 10;18(4):837-844. doi: 10.1039/c8pp00312b.
Ta3N5 nanotubes (NTs) were obtained from nitridation of Ta2O5 NTs, which were grown directly on Ta foil through a 2-step anodization procedure. With Co(OH)x decoration, a photocurrent density as high as 2.3 mA cm-2 (1.23 V vs. NHE) was reached under AM1.5G simulated solar light; however, the electrode suffered from photocorrosion. More stable photoelectrochemical (PEC) performance was achieved by first loading Co(OH)x, followed by loading cobalt phosphate (Co-Pi) as double co-catalysts. The Co(OH)x/Co-Pi double co-catalysts may act as a hole storage layer that slows down the photocorrosion caused by the accumulated holes on the surface of the electrode. A "waggling" appearance close to the "mouth" of Ta2O5 NTs was observed, and may indicate structural instability of the "mouth" region, which breaks into segments after nitridation and forms a top layer of broken Ta3N5 NTs. A unique mesoporous structure of the walls of the Ta3N5 NTs, which is reported here the first time, is also a result of the nitridation process. We believe that the mesoporous structure makes it difficult for the nanotubes to be fully covered by the co-catalyst layer, hence rationalizing the remaining degradation by photocorrosion.
Ta3N5 纳米管（NTs）是通过两步阳极氧化程序，直接在 Ta 箔上生长的 Ta2O5 NTs 氮化得到的。经过 Co(OH)x 修饰，在 AM1.5G 模拟太阳光照射下，光电流密度高达 2.3 mA cm-2（相对于 NHE 为 1.23 V）；然而，该电极遭受光腐蚀。通过先负载 Co(OH)x，然后再负载磷酸钴（Co-Pi）作为双共催化剂，实现了更稳定的光电化学（PEC）性能。Co(OH)x/Co-Pi 双共催化剂可能充当空穴存储层，减缓了电极表面累积空穴引起的光腐蚀。观察到接近 Ta2O5 NTs“口”的“摆动”外观，这可能表明“口”区域的结构不稳定，在氮化后会断裂成片段，并形成顶部破碎的 Ta3N5 NTs 层。这里首次报道了 Ta3N5 NTs 壁的独特介孔结构，这也是氮化过程的结果。我们认为介孔结构使得纳米管难以被共催化剂层完全覆盖，因此可以合理地解释光腐蚀引起的剩余降解。
