Operando tracking of turnover and site density modifications of Fe-N-C fuel cell cathodes

Abstract

Layered metal-halide perovskites have shown great promise for applications in optoelectronic devices, where a large number of suitable organic cations give the opportunity to tune their structural and optical properties. However, especially for Sn-based perovskites, a detailed understanding of the impact of the cation on the crystalline structure is still missing. By employing two cations, 2,2 0oxybis(ethylammonium) (OBE) and 2,2 0 -(ethylenedioxy)bis(ethylammonium) (EDBE), we obtain a planar h100i and a corrugated h110i-oriented perovskite, respectively, where the hydrogen bonding between the EDBE cations stabilises the corrugated structure. OBESnI 4 exhibits a relatively narrow band gap and photoluminescence bands compared to EDBESnI 4 . In-depth analysis shows that the markedly different optical properties of the two compounds have an extrinsic origin. Interestingly, thin films of OBESnI 4 can be obtained both in black and red colours. This effect is attributed to a second crystalline phase that can be obtained by processing the thin films at 100 1C. Our work highlights that the design of the crystal structure as obtained by ligand chemistry can be used to obtain the desired optical properties, whereas thin film engineering can result in multiple crystalline phases unique to Sn-based perovskites.10th Anniversary Statement written by Maria A. Loi I was a young post-doctoral fellow when, at that time Journal Material Chemistry, published my work on the photophysics and solar cells of phthalocyaninefulleropyrrolidine dyads and devoted the cover to the article. From that moment, I have been always considering the Journal Material Chemistry family, and especially Journal Material Chemistry C, as the perfect avenue for multidisciplinary works where new materials, deep spectroscopical investigation and even device investigations can be presented to a multifaceted community. The interdisciplinarity, breadth and plasticity in embracing the newest topics emerging from the community are the characteristics, that in my opinion, determine the continuous success of