Examination of Hydrogen Evolution Bubble Trapping in Ordered Porous 3D Printed Metal and Metal Oxide-Coated Microlattice Electrodes
Determining the nature of surface roughness and electrode pore structure on H2 bubble evolution rate and 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 provides 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 micro-lattice 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 influence of material activity, small scale surface roughness, and the larger substrate pore network on the traffic or 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 coated 3D printed electrodes are robust HER electrodes, allow efficient transport of small bubbles, but significant limitations are found for larger bubble transport through ordered porous microlattice shown through model simulations and experimental measurements.