A highly stable Cu(OH)2-Poly(vinyl alcohol) nanocomposite membrane for dramatically enhanced direct borohydride fuel cell performance

Nano-additive aggregation, limited performance, and unclear modification mechanisms are the main obstacles in developing nanocomposite anion exchange membranes (AEMs). In this work, for the first time, an effective and highly stable Poly(vinyl alcohol) (PVA)-based AEMs with dispersive Cu(OH)2 nanoclusters (Cu-AEMs) are prepared by a simple and eco-friendly three-step method: ‘CuCl2 doping-casting-KOH immersing’. The doped Cu2+ ions chemically combine with OH− ions to form anionic conductive Cu(OH)2 nanoclusters intermediated by attaching resins. The PVA skeletons wrap around Cu(OH)2 while the hydroxyl groups expose to bulk water, forming Cu(OH)2-PVA complex, which avoids nano-additive aggregation, increases anionic channels, and strengthens additive-matrix connection. A direct borohydride fuel cell using Cu-AEM with 0.56 wt % CuCl2 possess the highest power density of 403.3 mW cm−2 at 60 °C and a life span of over 200 h. The high-performance and durability come from the unique structure of Cu(OH)2 nanoclusters-PVA complex. ‘Vehicle’ theory is considered to be the dominant mechanism for enhancing such nanocomposite Cu-AEMs. This work demonstrates a new concept for preparing the stable AEMs toward high-performance fuel cells. The synthetic chemistry involved can be broadly extended for fabricating versatile AEMs.