Synthesis of amorphous metal oxides via a crystalline to amorphous phase transition strategy

Amorphous metal oxide (AMO) nanomaterials are attractive because of their unique short-range order structure, but controllable synthesis is still challenging. Here we report a Li + -assisted liquid-phase reduction method, which converts a series of crystalline metal oxides into amorphous structures (RuO x , PtO x , CuO x , NiO x , PdO x , MnO x and NiCoO x ). Taking RuO 2 as an example, in situ Raman and X-ray absorption spectroscopy indicate that the reduction of Ru–O coordination number and distortion of the medium-range structure of Ru–Ru during the amorphization process are caused by naphthalene radical anions and lithium ions. Theoretical calculations indicate that Li⁺ insertion in RuO x strengthens its electrostatic interaction with the naphthalene radical anion, accelerating the stripping of oxygen from Li⁺-inserted RuO x . The introduction of positive charge by Li⁺ insertion can disrupt the internal charge balance of crystal ruthenium oxide, and therefore reduce the formation energy of intermediates for producing amorphous RuO x . This strategy paves a way for achieving the controllable synthesis of AMOs.