A Topochemical Approach to Synthesize Layered Materials Based on the Redox Reactivity of Anionic Chalcogen Dimers

Abstract

Layered transition metal compounds represent a major playground to explore unconventional electric or magnetic properties. In that framework, topochemical approaches that mostly preserve the topology of layered reactants have been intensively investigated to tune properties and/or design new materials. Topochemical reactions often involve the insertion or deinsertion of a chemical element accompanied by a change of oxidation state of the cations only. Conversely, cases where anions play the role of redox centers are very scarce. Here we show that the insertion of copper into two dimensional precursors containing chalcogen dimers (Q ) (Q=S, Se) can produce layered materials with extended (CuQ) sheets. The reality of this topochemical reaction is demonstrated here for different pristine materials, namely La O S , Ba F S , and LaSe . Therefore, this work opens up a new synthetic strategy to design layered transition metal compounds from precursors containing polyanionic redox centers.

Solvothermal and mechanochemical intercalation of Cu into La2O2S2 enabled by the redox reactivity of (S2)2− pairs

“…In the following we discuss the details of each experimental approach. We already reported the solid-solid reaction between La2O2S2 and metallic Cu powder, 10 which led to the complete conversion of the precursor into the intercalated phase La2O2Cu2S2 within two times 1 hour annealing at 250 °C with the intermediate grinding step. The obtained La2O2Cu2S2 phase featured relatively broad XRD peaks compared to those prepared at high temperature (T = 700 °C).…”

“…1) to achieve intercalation of transition metal atoms such as Cu, Ni and Fe. [10][11] This way to proceed differs significantly from reported mechanisms so far where redox centres are commonly based on cations. Namely, electrons are here transferred from zerovalent metal to chalcogen dimers (or oligomers in general) contained in layered polychalcogenides, leading to the cleavage of the anion-anion bonds and concomitant intercalation of metal cations.…”

“…The precursor La2O2S2 was prepared as the yellow powder following the method previously reported. 10 CuCl (Aldrich, > 98%), ethylenediamine (Alfa Aesar, 99%) and Cu powder (Alfa Aesar, 100-325 mesh, 99.9%) were purchased and used without further purification. La2O2S2 and CuCl were weighed in the 1 : x molar ratios (x = 2.0, 2.56 and 4.0) and placed in a 25 mL Teflonline autoclave.…”

Solid state chemistry for developing better metal-ion batteries

“…However, the long-believed anionic redox intercalation chemistry related to forming/breaking polysulfide S-S bonds still needs a solid crystallographic confirmation. In a broader context, such redox chemistry is recently demonstrated for the low-temperature insertion of Cu into La 2 O 2 S 2, Ba 2 S 2 F 2, LaSe 2 , BaS 2 containing (L 2 ) 2− (L = S, Se) dimers to obtain the Cu 2 La 2 O 2 S 2, Ba 2 Cu 2 S 2 F 2 , LaCuSe 2 and BaCu 2 S 2 phases 14 . Through this insertion, metallic Cu donates electrons from 3 d orbitals to low-lying σ* orbitals of the (L 2 ) 2− dimers causing their cleavage.…”

Unexplored reactivity of (Sn)2− oligomers with transition metals in low-temperature solid-state reactions

“…Ni 2+ and Fe 2+ in square-pyramidal and tetrahedral sites, respectively) can be inserted into (Sn) 2containing precursors at temperatures (T = 340 °C) much lower than the ones (T > 800 °C) needed for conventional ceramic routes for BaNiS2 and BaFe2S3. [39][40][41] In our previous report, 21 insertion of copper into (S2) 2containing materials were shown to be topochemical. The same observation is made here as demonstrated below for BaNiS2 and BaFe2S3 ( Fig.…”