Cable‐Car Electrocatalysis to Drive Fully Decoupled Water Splitting

Abstract

The increasing demand for clean energy conversion and storage has increased interest in hydrogen production via electrolytic water splitting. However, the simultaneous production of hydrogen and oxygen in this process poses a challenge in extracting pure hydrogen without using ionic conducting membranes. Researchers have developed various innovative designs to overcome this issue, but continuous water splitting in separated tanks remains a desirable approach. This study presents a novel, continuous roll‐to‐roll process that enables fully decoupled hydrogen evaluation reaction (HER) and oxygen evolution reaction (OER) in two separate electrolyte tanks. The system utilizes specially designed “cable‐car” electrodes (CCE) that cycle between the HER and OER tanks, resulting in continuous hydrogen production with a purity of over 99.9% and Coulombic efficiency of 98% for prolonged periods. This membrane‐free water splitting system offers promising prospects for scaled‐up industrial‐scale green hydrogen production, as it reduces the cost and complexity of the system, and allows for the use of renewable energy sources to power the electrolysis process, thus reducing the carbon footprint of hydrogen production.

Breaking boundaries: advancements in solid-state redox mediators for decoupled water electrolysis

“…Interestingly, Wu and colleagues drew inspiration from the cable car model to develop a novel "cable-car" electrode (CCE) structure capable of uninterrupted hydrogen production from Ni(OH) 2 . 91 A schematic diagram of the device is shown in Fig. 10, wherein the transfer module is used to transfer CCEs so that the Ni(OH) 2 electrode alternates between hydrogen and oxygen tanks.…”

Advanced Device Architecture Strategies for Decoupled Water Splitting: A Review

“…Membranes can occupy more than 24% volume in the case of a PEM in the electrolyzer stack. 54 Further, the cyclic stability of soluble RMs may limit the decoupling process, particularly as they are diffusing in solution and may find reactive pairs. In the next subsections, we describe ways to address such limitations with different strategies.…”

“…Long et al reported a similar device for decoupling HER and OER processes but used AE as a running cable car that cycles multiple AEs between the chambers (Figure 9). 54 The process worked with the application of an external voltage of at least 1.4 V for HER, and less than 0.9 V is applied for OER at 50 mA cm −2 . For 20 mA cm −2 , less than 0.5 V is required for OER.…”

“…Moreover, an ion-exchange membrane is needed, which sometimes hampers the efficiency of the overall device and also increases their cost. Membranes can occupy more than 24% volume in the case of a PEM in the electrolyzer stack . Further, the cyclic stability of soluble RMs may limit the decoupling process, particularly as they are diffusing in solution and may find reactive pairs.…”

“…Decoupled EWS using Ni­(OH) 2 /NiOOH AE employing a cable car-like strategy for transporting the electrodes between different compartments. Reprinted with permission under a Creative Commons CC BY License from ref . Copyright 2023, John Wiley and Sons.…”