Synthesis of multicomponent oxygen evolution reaction coatings via block copolymer templating with vapor- and...

Porous mixed transition metal oxide heterostructures are promising electrocatalysts due to their high surface area. However, achieving conformal multicomponent oxide coatings with controlled nanoscale architectures remains challenging. Here, we report a synthesis strategy that integrates solution-based swelling infiltration (SBI) with gas-phase sequential infiltration synthesis (SIS) in a block copolymer template to fabricate porous, high-surface-area, conformal mixed-oxide electrocatalytic coatings. In this approach, a PS75-P4VP25 block copolymer (BCP) film is first infiltrated with transition metal acetylacetonate precursors via SBI, followed by exposure to gas phase precursors of ZnO via SIS process. Thermal annealing of the infiltrated BCP films converts them into all-inorganic Fe-ZnO, Fe-Co-ZnO, and Fe-Ni-ZnO coatings. Electrochemical testing on 70 nm thick conformal coatings demonstrates promising oxygen evolution reaction (OER) activity in alkaline media, with mass-specific current densities up to 1.0 × 10⁵ mA/g at an overpotential of 330 mV (vs. RHE) at ultralow loading (∼0.005 g/cm²). Among the compositions, Fe-Co-ZnO and amorphous Fe-Ni-ZnO show the best OER performance, delivering current densities of 2.00 and 3.04 mA/cm², respectively, compared to 1.52 mA/cm² for Fe-ZnO. This work establishes SBI-SIS as a versatile route for fabricating nm-thin, high-performance multicomponent oxide heterostructures on cost-efficient supports, enabling efficient catalyst utilization in electrochemical energy conversion applications.