The Renewed Interest on Brunogeierite, GeFe2O4, a Rare Mineral of Germanium: A Review

Abstract

GeFe2O4, also known as brunogeierite, is a rare mineral of germanium. It has a normal spinel structure and, as with many other spinels, amazing functional properties thanks to its peculiar structural features. In the past, its spectroscopic, optical, magnetic and electronic properties were determined; then, for many years, this compound was left behind. Only recently, a renewed interest in this oxide has arisen, particularly for its application in the electrochemical field. In this review paper, the crystal structure of GeFe2O4 will be described, as well as the synthesis methods required to obtain single crystals or polycrystalline powders. Its spectroscopic, magnetic, optical and electrical properties will be reported in detail. Then, successful applications known so far will be described: its use as anode in Lithium Ion and Sodium Ion Batteries and as electrocatalyst for urea oxidation reaction.

Effect of Mn Substitution on GeFe2O4 as an Anode for Sodium Ion Batteries

“…Moreover, some octahedral particles emerged from the aggregates, suggesting the presence of a magnetite phase related to the iron excess used during the GFO synthesis [20]. In the literature, in fact, a partial solubility of GFO and Fe 3 O 4 was also reported for the natural mineral, often containing some amount of Fe 3+ ions [10]. Similar octahedral forms were detected in the micrographs of GFO reported in other papers [16,21].…”

“…In this regard, germanium ternary oxides have been considered as novel alternatives for SIBs thanks to their ability to incorporate more than one Na + ion, allowing significantly high theoretical capacities. Within this family, GeFe 2 O 4 (GFO) stands out as a promising SIB anode material [10] thanks to its low toxicity, environmental friendliness, and especially high theoretical specific capacity due to the combination of its conversion and alloying reactions, as represented in equations 1-3 below: Fe 2 GeO 4 + 8Na + + 8e − → 2Fe + Ge + 4Na 2 O…”

Pure and (Sn or Mg) Doped GeFe2O4 as Anodes for Sodium-Ion Batteries

“…Ge has a limited number of natural minerals that are rare and not widespread on the Earth's crust [17]. Between these compounds, Ge-based ternary oxides, in particular, have been recently proposed as anodes for both LIBs and SIBs due to good electrochemical performances allowed by their unique reaction mechanism, i.e., a combination of conversion and alloying [18,19].…”

“…It has a peculiar story: the identification of the correct cation oxidation states was difficult, and for many years, a lot of uncertainty about them remained. It was then established that the right structure was Ge 4+ Fe 2+ 2 O 4 [17,23], which differed from the large part of normal spinels having 2+ and 3+ ions in tetrahedral and octahedral sites, respectively.…”

Structural evolution and electronic properties of cerium doped germanium anionic nanocluster CeGen− (n = 5–17): Theoretical investigation

“…According to various designs, these nanomaterials possess a range of applications across diverse fields. For instance, they serve as high‐efficiency quantum dots light‐emitting diodes [3], as solar cell photovoltaic power generation film to utilize solar energy [4], and as exceptional catalysts for photocatalysis or electrocatalysis depending on the proper bandgap of materials [5, 6], ultrafast photodetector and highly stable solid‐state batteries [7, 8], etc. Despite the widespread use of silicon‐based materials, germanium offers unprecedented advantages as a substitute for silicon, particularly for high‐mobility charge carriers, a lower band gap to achieve higher saturation velocity and reduced leakage current, which translates into lower drive needed to enhance or maintain devices performance [9–11].…”