Transforming 3D Printed Polymer Microlattices into High-Performance Co/CoO_x/C Electrodes for Water Splitting

Additive manufacturing offers an opportunity to push the limits of electrocatalyst performance and stability via deep control over gas and liquid phase mass-transport from the nanoscale to the mesoscale. Here, we report a generalizable method known as polymer infusion additive manufacturing (PIAM) for transforming 3D printed polymers into microlattice electrodes for electrocatalytic water splitting in alkaline media. Our method produces core-shell structured free-standing microlattices bearing nanoporous functional transition metal / metal oxide heterointerfaces suitable for performing both hydrogen evolution (Cu/CuO_x/C) as well as oxygen evolution (Co/CoO_x/C). In this talk we focus on the 3D printing of Co/CoO_X/C microlattice electrodes that displaying exceptional electrocatalytic activity with an extremely low overpotential (1.40 V to reach 10 mA/cm²). This overpotential of Co/CoO_x for OER is, to our knowledge, among the best reported PGM-free electrodes.<br/> <br/>The outstanding electrocatalytic performance and long-term stability of 3D microlattice electrodes leverages their mesoscale (100-300 μm) pores, providing accessibility of electrolytes within the structures, maximizing the utilization of active sites, and ensuring the rapid discharge of gas bubbles for promoting electrode stability. We explore the gas phase mass-transport properties of these 3D printed microlattices via microscopic imaging of bubble evolution. Through direct comparison of periodic lattices and random foams, we reveal how the high electrochemical stability of these electrodes may be attributed to the rapid elimination of gas bubbles within 3D lattices with aligned pores. These results provide a viable route to fabricating free-standing, integrated catalyst / electrode structures in a single scalable process with a high degree of design freedom, simultaneously optimizing liquid and gas-phase mass-transport beyond the fundamental limits of random porous foams.