A new class of 'bubble-free' alkaline electrolyzer with electrodes comprising of PTFE-based Gortex gas diffusion layers coated with catalysts, is described (PTFE = poly(tetrafluoroethylene)). At >= 80 degrees C (E degrees (cell) 1.18 V), the electrolyzers displayed the lowest cell onset potentials (>= 1.28 V) yet reported, indicating that they exhibit the highest-known intrinsic efficiency when the influence of impedance is stripped out. The over-potentials at each electrode, particularly the oxygen-generating anode, were significantly diminished by the presence of the porous Gortex substrate, which exhibited a powerful 'gas-philic' capillary action (6.3 bar capillary pressure). The bubble-free process arose from preferential coalescence of newly-formed gases on the PTFE surfaces, where the capillary action of the Gortex continuously extracted them before they could nucleate bubbles. In so doing, observable bubble formation was avoided, along with the energy penalties associated with the formation and release of gas bubbles. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.