Hydrogen Evolution Reaction Bubble Traffic in Coated 3D-Printed Microlattice Electrodes

Determining the nature of surface roughness and electrode pore structure on H2 bubble evolution rate, quantity and bubble trapping under electrolytic conditions is important for quantifying useful gas production during total water-splitting and hydrogen evolution reactions. Controlled electrode systems, involving the design of geometry, surface area, and porosity, provide options to understand trapped/redissolved gas bubble evolution and improve overall efficiency. In this study, we use vat polymerization (Vat-P) 3D printing to create ordered microlattice electrode structures from metal and metal-oxide-coated photopolymerized methacrylate-based resins. These microlattice structures are designed with various geometries to influence bubble traffic from gas nucleation and evolution during electrochemical HER processes. Using cyclic and linear sweep voltammetry and chronopotentiometry, this work analyzes the response of metallized (NiO/Ni(OH)2 and Au) microlattice HER electrodes as a function of geometric structure, to gauge the influence of material activity, small-scale surface roughness, and the larger substrate pore network on the traffic of larger bubbles, formed during HER. This work also uses broadband acoustic resonance dissolution spectroscopy (BARDS) to quantify bubble evolution and reabsorption in the electrolyte during electrolysis. The results show that 3D-printed electrodes with defined pore geometries, coated with materials that are active or less active for HER, allow efficient transport of small bubbles, while significant limitations are found for larger bubble transport.