Synthesis of noble metal nanoarrays via agglomeration and metallurgy for acidic water electrolysis

Noble metal electrocatalysts remain the mainstay for proton exchange membrane water electrolysis, majorly due to their exceptional activity and durability in acidic media. However, conventional powder and particle catalysts intensively suffer from aggregation, shedding and poor electron conductivity in practical applications. Here, we develop a micellar brush-guided method to agglomerate and smelt metal nanoparticles into erect nanoarrays with designable constitutions on various substrates. While the nanoarrays of stacked nanoparticles show poor stability in the acidic media, the smelting treatment substantially enhances the electron conductivity by more than four order of magnitude and reinforces the nanoarray architectures. This allows the tailored fabrication of self-supported acid-durable metallic and alloy nanoarray catalysts with outstanding hydrogen evolution activity, and metal oxide nanoarray with extraordinary oxygen evolution activity. The integration of metallic Ru-nanoarray and RuO_x-nanoarray in a proton exchange membrane electrolyzer further enables a long-term stable water electrolysis process for more than 500 h at 1 A cm⁻².