Ion exchange membranes are widely used to selectively transport ions in various electrochemical devices. Hydroxide exchange membranes (HEMs) are promising to couple with lower cost platinum-free electrocatalysts used in alkaline conditions, but are not stable enough in strong alkaline solutions. Herein, we present a Cu²⁺-crosslinked chitosan (chitosan-Cu) material as a stable and high-performance HEM. The Cu²⁺ ions are coordinated with the amino and hydroxyl groups of chitosan to crosslink the chitosan chains, forming hexagonal nanochannels (~1 nm in diameter) that can accommodate water diffusion and facilitate fast ion transport, with a high hydroxide conductivity of 67 mS cm⁻¹ at room temperature. The Cu²⁺ coordination also enhances the mechanical strength of the membrane, reduces its permeability and, most importantly, improves its stability in alkaline solution (only 5% conductivity loss at 80 °C after 1,000 h). These advantages make chitosan-Cu an outstanding HEM, which we demonstrate in a direct methanol fuel cell that exhibits a high power density of 305 mW cm⁻². The design principle of the chitosan-Cu HEM, in which ion transport channels are generated in the polymer through metal-crosslinking of polar functional groups, could inspire the synthesis of many ion exchange membranes for ion transport, ion sieving, ion filtration and more.

离子交换膜广泛用于在各种电化学装置中选择性地传输离子。氢氧化物交换膜 (HEM) 有望与在碱性条件下使用的低成本无铂电催化剂结合使用，但在强碱性溶液中不够稳定。在此，我们提出了一种 Cu ²⁺交联壳聚糖（壳聚糖-Cu）材料作为一种稳定且高性能的 HEM。Cu ²⁺离子与壳聚糖的氨基和羟基配位，交联壳聚糖链，形成六角形纳米通道（直径约 1 nm），可容纳水扩散并促进快速离子传输，具有 67 mS 的高氢氧化物电导率cm ^-1在室温下。铜²⁺协调还增强了膜的机械强度，降低了它的渗透性，最重要的是，提高了它在碱性溶液中的稳定性（1000 小时后在 80 °C 下仅损失 5% 的电导率）。这些优势使壳聚糖铜成为出色的 HEM，我们在直接甲醇燃料电池中展示了这一点，该燃料电池具有 305 mW cm ^-2的高功率密度。壳聚糖-Cu HEM 的设计原理，其中通过极性官能团的金属交联在聚合物中产生离子传输通道，可以激发许多用于离子传输、离子筛分、离子过滤等的离子交换膜的合成。