Hydrogen Production with a Simple and Scalable Membraneless Electrolyzer

Abstract

Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H 2 ) when operated at 100 mA cm −2 . Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H 2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm −2 and fluid velocity of 26.5 cm s −1 . Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance. Solar and wind energy have the potential to power the planet without the environmental impact of fossil fuels, but encounter significant challenges to widespread adoption due to their low capacity factors and inherent intermittency.1 In order to overcome this challenge, affordable grid-scale energy storage technology is needed that can make electricity generation from these technologies more widespread.2 One solution to this issue is to convert excess renewable electricity into stored chemical energy in the form of hydrogen gas (H 2 ), 3 which represents a promising candidate for grid scale energy storage and as a carbon-free replacement of fossil fuels in the transportation and industry sectors. 4 Electrolyzers, which use electricity and water to produce hydrogen and oxygen, are well-established commercially available technologies, 5 but the cost of producing H 2 by water electrolysis is currently too expensive.6-8 Presently, much of the cost of producing H 2 by water electrolysis comes from the price of electricity, 6,8 but as the price of electricity from wind and solar continues to decrease and time-of-use pricing schemes become more prevalent, decreasing the cost of electrolyzer technology will be of great importance to making a renewable hydrogen future a reality.The majority of electrolyzers are based on a design in which the cathode and anode are separated by an ion-conducting membrane or diaphragm. 9 The two most common types of electrolyzers are alkaline and polymer electrolyte membrane (PEM) electrolyzers, which are able to electrolyze alkaline and ultra-pure water, respectively. These electrolyzers are mature t...

Pathways to electrochemical solar-hydrogen technologies

“…In addition to standard cationexchange-membrane-based electrolyzers, membrane-free systems have seen significant advances due to their tolerance for impurities in water feedstock and potentially lower upfront capital costs. [92][93][94][95] Moreover, the development of anion-exchange membranes can enable implementation of alkaline polymerelectrolyte-membrane electrolyzers that use high-performing and earth-abundant Ni-based catalysts. 96,97 These membranes must exhibit long-term stability and avoid excessive gas crossover even at lower sunlight-driven rates.…”

Inertial manipulation of bubbles in rectangular microfluidic channels

“…12 Removing the solid membrane in these systems decreases the ohmic losses and provides flexibility in the selection of catalysts in addition to a simplified cell design. [13][14][15][16] Controlling two-phase flows by topography induced variations of the bubbles' surface energy is another way of eliminating the need for a functional membrane. 17 In this paper, we implement experimental and numerical tools to investigate the dynamics of bubbles flowing in microfluidic channels.…”

Membraneless Electrolyzers for Low-Cost Hydrogen Production in a Renewable Energy Future

“…14 More recently, a type II design was demonstrated that was based on angled mesh flow-through electrodes separated by an insulating baffle that was part of the device body. 15 This modification enabled the use of an extremely simple device body that was 3D printed as a single, monolithic component, and was furthermore amenable to in situ imaging of the crossover phenomenon and non-uniform current densities with high-speed video analysis.…”