Fig. 2: Highly thermally conductive composite HEM.

a Schematic diagram of HEMWE in which the BN composite HEM with a 3D thermally conductive network is applied. Composite HEM exhibits fast heat diffusion, thereby potentially reducing the localized temperature and promoting the in-situ stability of HEM in a water electrolyzer. b Design of BN composited HEM, where phonon and hydroxide transport along the 3D network. c, d Side-view SEM image of the QCS/3.8%BN and QCS/10.6%BN membranes, respectively. The structure of QCS/BN membranes is indicated in insets. e Thermal conductivity of QCS/BN membranes with different BN volume fractions. Inset: Photo of pure QCS and QCS/10.6%BN. Data in (e) are presented as mean values ± standard deviation based on at least three trials. f Infrared photos of membranes with a square region cooling from 60 °C to 10 °C.