Template-free synthesis of mesoporous and amorphous transition metal phosphate materials

Abstract

We present how mesoporosity can be engineered in transition metal phosphate (TMPs) materials in a template-free manner. The method involves a transformation of a precursor metal phosphate phase, called M-struvite...

Thermally processed Ni-and Co-struvites as functional materials for proton conductivity

“…The humidity and heating time/rate can significantly influence the phase stability and crystallinity, especially in the low T -region below 400 °C. This ability of M-struvite to sequentially convert into various amorphous and crystalline transition metal phosphate phases opens the space for possible crystal and phase engineering and upcycling of the waste-derived struvite 29,40,50,51 into tailored TMPs, as we indeed explore below.…”

“…In addition, TMPs with tuneable mesoporous frameworks can be synthesized either by using template-based 3,14,20 or template-free methods. 29 Thus, these materials can be obtained in many form factors such as bulk ceramics, thin films, or membrane materials. [30][31][32] Due to the different condensation degrees of the phosphate units and variable exchangeable metal cations, TMPs provide a wide range of chemical compositions.…”

Nonclassical Crystallization Pathway of Transition Metal Phosphate Compounds

“…In theory, both metals can be incorporated into the crystalline phases considered to form solid solutions. , However, upon precipitation from aqueous solution, the starting aqueous ionic concentrations and the final metal composition in the crystals differ significantly. Therefore, the occurring crystalline phases are named M-struvite and M-octahydrate with M = Ni x Co 1– x .…”

“…Transition metal ions are toxic pollutants, especially in groundwater and wastewater. Therefore, coprecipitation of phosphate and transition metal-bearing phases from various waste streams of agricultural, industrial, or mining origin (tailings, sludge, wastewaters) is a viable extraction and recycling method to yield transition metal phosphates (TMPs). , Such materials could be further upcycled into processed, higher value compounds suitable for applications. For example, transition metal phosphates, such as Zr, Sn, Ni, or Co phosphates, garnered attention as low-cost, chemically stable, and tunable proton conductors for fuel cells. − However, to effectively harvest metal and phosphate in the form of TMPs and convert them to functional materials, one must elucidate their nucleation and crystallization pathways from aqueous solutions.…”

“…Therefore, coprecipitation of phosphate and transition metal-bearing phases from various waste streams of agricultural, industrial, or mining origin (tailings, sludge, wastewaters) is a viable extraction and recycling method to yield transition metal phosphates (TMPs). 4,5 Such materials could be further upcycled into processed, higher value compounds suitable for applications. For example, transition metal phosphates, such as Zr, 6 Sn, 7 Ni, or Co 8 phosphates, garnered attention as low-cost, chemically stable, and tunable proton conductors for fuel cells.…”