Chemin Arsène, Levine Igal, Rusu Marin, Vaujour Rémi, Knittel Peter, Reinke Philipp, Hinrichs Karsten, Unold Thomas, Dittrich Thomas, Petit Tristan
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109, Berlin, DE, Germany.
École Normale Supérieure de Lyon, Lyon, 69342, France.
Small Methods. 2023 Nov;7(11):e2300423. doi: 10.1002/smtd.202300423. Epub 2023 Aug 18.
Solvated electrons are highly reductive chemical species whose chemical properties remain largely unknown. Diamond materials are proposed as a promising emitter of solvated electrons and visible light excitation would enable solar-driven CO or N reductions reactions in aqueous medium. But sub-bandgap excitation remains challenging. In this work, the role of surface states on diamond materials for charge separation and emission in both gaseous and aqueous environments from deep UV to visible light excitation is elucidated. Four different X-ray and UV-vis spectroscopy methods are applied to diamond materials with different surface termination, doping and crystallinity. Surface states are found to dominate sub-bandgap charge transfer. However, the surface charge separation is drastically reduced for boron-doped diamond due to a very high density of bulk defects. In a gaseous atmosphere, the oxidized diamond surface maintains a negative electron affinity, allowing charge emission, due to remaining hydrogenated and hydroxylated groups. In an aqueous electrolyte, a photocurrent for illumination down to 3.5 eV is observed for boron-doped nanostructured diamond, independent of the surface termination. This study opens new perspectives on photo-induced interfacial charge transfer processes from metal-free semiconductors such as diamonds.
溶剂化电子是极具还原性的化学物种，其化学性质在很大程度上仍不为人知。金刚石材料被认为是溶剂化电子的一种有前景的发射体，可见光激发将能够在水性介质中实现太阳能驱动的CO或N还原反应。但亚带隙激发仍然具有挑战性。在这项工作中，阐明了金刚石材料表面态在气态和水性环境中从深紫外到可见光激发下对电荷分离和发射的作用。四种不同的X射线和紫外-可见光谱方法被应用于具有不同表面终止、掺杂和结晶度的金刚石材料。发现表面态主导亚带隙电荷转移。然而，由于大量缺陷的密度非常高，硼掺杂金刚石的表面电荷分离急剧降低。在气态气氛中，由于残留的氢化和羟基化基团，氧化的金刚石表面保持负电子亲和力，从而允许电荷发射。在水性电解质中，对于硼掺杂的纳米结构金刚石，观察到低至3.5 eV光照下的光电流，与表面终止无关。这项研究为来自无金属半导体（如金刚石）的光诱导界面电荷转移过程开辟了新的视角。
