3D Printed Microlattices of Transition Metal/ Metal Oxides for Highly Stable and Efficient Water Splitting

Abstract

Developing affordable electrocatalysts is crucial for driving the sustainable energy transition to green hydrogen. Here, we report a generalizable method known as polymer infusion additive manufacturing (PIAM) for transforming 3D printed photopolymers into core-shell microlattice electrodes for electrocatalytic water splitting with transition metal/metal oxides/carbon heterointerfaces. The optimized free-standing architectures integrate Cu/CuOx on carbon (Cu/CuOx/C) microlattices, yielding high electrocatalytic activity (overpotential of 145 mV at 10 mA/cm2 and a Tafel slope of 134 mV/dec) and excellent durability for HER (>100 hr), surpassing state-of-the-art Cu foams. Additionally, for oxygen evolution (OER), Co/CoOx on carbon (Co/CoOx/C) microlattices display exceptional activity with the lowest overpotential (1.40 V to gain 10 mA/cm2) among all reported PGM-free electrodes. We explore the gas phase mass-transport properties of these 3D microlattices via microscopic imaging of bubble evolution, finding that the outstanding electrocatalytic performance and long-term stability of microlattice electrodes leverages their mesoscale (100-300 μm) pores, providing accessibility of electrolytes, maximizing utilization of active sites, and ensuring rapid evolution of gas bubbles. Thus, we introduce a simple but pioneering method for manufacturing 3D mesostructured electrocatalysts with deep control of liquid and gas phase mass-transport, enhancing the efficacy of alkaline water electrolysis.