Solvation Effect-Determined Mechanisms of Cation Exchange Reactions for Efficient Multicomponent Nanocatalysts.

Cation exchange (CE) reaction is a classical synthesis method for creating complex structures. A lock of study on intrinsic mechanism limits its understanding and practical application. Using X-ray absorption spectroscopy, we observed that the evolution from Ru-Cl to Ru-O/OH occurs during the CE between KRuCl and CoSn(OH) in aqueous solution, while CE between KPtCl and CoSn(OH) is inhibited due to the failure of structural evolution from Pt-Cl to Pt-O/OH. Theoretical simulations imply that the interaction between Ru-O and CoSn(OH) with Co vacancy (CoVSn(OH)) endows the electron transfer, as a result of strengthened adsorption on CoVSn(OH). Moreover, this mechanism is validated for CE between KRuCl and ASn(OH) (A=Mg, Ca, Mn, Co, Cu, Zn), and CE between KPdCl/NaRhCl/KIrCl and CoSn(OH). Impressively, the Pt-free CoRuSn(OH) produced via CE displays a mass activity and a power density of 15.0 A mg and 11.6 W mg , respectively, for anion exchange membrane fuel cell (AEMFC) exceeding the values of commercial PtRu/C (11.8 A mg and 9.0 W mg ). This work, for the first time, reveals the intrinsic mechanism of CE as structural evolution of target ion breaking through the traditional classic etch-adsorption mechanism and will promote fundamental research and practical application in various fields.