3D Printed Continuous Nanoporous Cu/CuOx Electrodes for Highly Efficient Hydrogen Evolution Reaction

The sluggish kinetics of electrocatalysts in alkaline media cause stability as well as low active site issues, restricting the conversion of renewable energy into hydrogen. Synergistic enhancements such as the formation of free-standing nanoporous heterostructures, homogeneous diffusion of active materials into conductive supports, and atomic doping/defecting of active materials could promise to improve the kinetics and resolve key stability issues. Herein, we present scalable 3D-printing of continuous nanoporous Cu/CuO_xdiffused carbon electrocatalysts for efficient alkaline hydrogen evolution reaction (HER) in which Cu/CuO_xacts as active sites, nanoporous carbon provides a higher conductive surface area to enhance HER kinetics, and periodic 3D lattice micro-structuring facilitates bubble evolution to improve stability. The resulting micro-architected porous electrodes deliver high electrocatalytic activity for HER, with an overpotential of 155 mV at a current density of 10 mA/cm² and a Tafel slope of 134 mV/dec, outperforming other 3D noble metal-free oxide materials. In addition, the as-fabricated catalysts also showed superior durability: up to 240 hours of continuous hydrogen evolution without any significant change in overpotential and current density, which is 10X better than reported 3D-printed catalysts. Our comparative analysis of multiple 3D lattice geometries indicates that our 3D-ordered nanoporous Cu/CuOx electrocatalysts maximize performance by exposing more active sites and allowing faster discharge of H₂ gas bubbles through engineered microchannels. We will finally discuss how our micro-architected approach to transforming 3D-printed lattices can be applied to a variety of earth-abundant electrocatalysts based on transition metal/metal oxides for enhancing performance and stability of additional reactions including OER.