NiFeOx decorated Ge-hematite/perovskite for an efficient water splitting system

Abstract

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeOx@Ge-PH photoanode shows a photocurrent density of 4.6 mA cm−2 at 1.23 VRHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm−2 in NiFeOx@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design.

Sn-Controlled Co-Doped Hematite for Efficient Solar-Assisted Chargeable Zn–Air Batteries

“…Photoelectrochemical (PEC) water splitting exploits a promising mechanism that generates clean energy by which water produces hydrogen and oxygen gases with the help of photogenerated electron–hole pairs . Hematite is a promising PEC material due to its abundant quantity, low cost, appropriate band gap, and excellent stability in an aqueous solution. − However, the application of hematite has been limited due to its very low solar-to-hydrogen conversion efficiency of 4–5% compared to the theoretical efficiency of 15.5% because of a high recombination rate, low bulk conductivity, low surface reaction kinetics, and sluggish charge transport property. − Many methods have been suggested to address these drawbacks, including elemental doping, heterojunction construction, development of nanostructures, and surface passivation. − Among them, doping with various heteroatoms such as Ti, − Si, − Ge, − Sn, − and other dopants has been widely applied to produce high-efficiency photoelectrodes by resolving the low bulk conductivity issue and sluggish surface reaction kinetics of hematite.…”

Recent research progress on operational stability of metal oxide/sulfide photoanodes in photoelectrochemical cells

“…Although the loading of the OECs and passivation layer improves the stability of the photoanode, introducing interfacial defects in the process of supporting the OECs often worsens the photoanode stability [89,90]. To address the interfacial defects between the OECs and photoanode interface, researchers usually support the OECs by in situ techniques or by introducing an interfacial layer [91,92].…”

Ideal dopant to increase charge separation efficiency in hematite photoanodes: germanium

“…23,24 Recently, several theoretical and experimental studies have highlighted the beneficial effect of germanium (Ge) as an additive to improve the photocurrent of hematite photoanodes. 25–31 After analyzing the experimental studies, we observed a clear dependence of the photoelectrochemical performance of the hematite photoanodes on the synthesis route used to introduce Ge. 31 This dependence is associated with the low chemical compatibility between α-Fe 2 O 3 and GeO 2 .…”