Modular Design of Noble-Metal-Free Mixed Metal Oxide Electrocatalysts for Complete Water Splitting.

Electrocatalytic water splitting into H2 and O2 is a key technology for carbon-neutral energy. Here, we report a modular materials design leading to noble metal-free composite electrocatalysts, which combine high electrical conductivity, high OER and HER reactivity and high durability. The scalable bottom-up fabrication allows the stable deposition of mixed metal oxide nanostructures with different functionalities on copper foam electrodes. The composite catalyst shows sustained OER and HER activity in 0.1 m aqueous KOH over prolonged periods (t>10 h) at low overpotentials (OER: ≈300 mV; HER: ≈100 mV) and high faradaic efficiencies (OER: ≈100 %, HER: ≈98 %). The new synthetic concept will enable the development of multifunctional, mixed metal oxide composites as high-performance electrocatalysts for challenging energy conversion and storage reactions.