Rationally Designing Efficient Electrocatalysts for Direct Seawater Splitting: Challenges, Achievements, and Promises

Abstract

Directly splitting seawater to produce hydrogen provides a promising pathway for energy and environmental sustainability. However, current seawater splitting faces many challenges because of the sluggish kinetics, the presence of impurities, membrane contamination, and the competitive chloride oxidation reaction at the anode, which makes it more difficult than freshwater splitting. This Review firstly introduces the basic mechanisms of the anode and cathode reactions during seawater splitting. We critically analyze the primary principles for designing catalysts for seawater splitting in terms of both the hydrogen and oxygen evolution reactions, including with noble metal, noble metal free, and metal‐free catalysts. Strategies to design effective catalysts, such as active site population, synergistic effect regulation, and surface engineering, are discussed. Furthermore, promises, perspectives, and challenges in developing seawater splitting technologies for clean hydrogen generation are summarized.

Designing electrocatalysts for seawater splitting: surface/interface engineering toward enhanced electrocatalytic performance

“…61,62 However, the corrosion caused by free Cl − is difficult to avoid, especially for metal-based catalysts. With long-term immersion in seawater, the free Cl − adsorbs on the electrode surface and gradually corrodes the catalyst by forming metal chloride-hydroxides, as in eqn ( 8)- (10). 23,61 Adsorption of Cl − by surface polarization:…”

“…18,23,35,36 Among these, catalyst design has received significant attention as a crucial component. Based on material types, Wang et al 13 sorted out the key points of catalyst activity regulation, while Wu et al 10 proposed activity regulation strategies, and Khatun et al 25 also put forward catalyst design strategies for selectivity and stability. As a multifunctional modulation strategy, there is an extensively growing interest in using surface/interface engineering to enhance the catalytic activity of seawater electrolysis catalysts, but insufficient attention has been paid to the regulation of selectivity and stability.…”

“…[4][5][6] Among the various energy conversion/storage technologies, hydrogen is considered to be the most promising path due to its high energy density, clean exhausts, easy conversion and mature supporting facilities. [7][8][9][10] Notably, the current tremendous endeavours in electrochemical water splitting mainly focus on purified water systems, inevitably limiting the spread of their application in areas of fresh water scarcity, such as the Middle East and North Africa. [11][12][13][14] For this reason, researchers have proposed an electrochemical seawater split-ting method that directly uses natural seawater as the hydrogen source, aiming to convert abundant seawater into hydrogen for energy storage.…”

Electrochemical Approach for Advanced Flow Reactors via Additive Manufacturing of High Surface Area Ti‐6Al‐4V Anode

“…To make electrochemical processes viable, highly efficient anodes are necessary to enhance the anodic reaction [4] . Noble metal‐based anodes are widely used in such electrochemical processes [5] . However, several factors hinder their practical applications in electrochemical reactors, such as overpricing, limited supply, and poor stability of noble metals [6] .…”

Energy-saving and sustainable saline-base electrolytic hydrogen production system enabled by nickel sulfide-based catalysts

“…To solve the above problems, some effective and inspiring strategies have been proposed. (i) Design of selective, active, and corrosion-resistant seawater HER/OER catalysts; 14,17,19,20 (ii) introduction of alternative anodic oxidation reactions to replace the saline/seawater OER; 21 (iii) construction of an alkaline seawater electrolysis system to improve the OER occurrence conditions and inhibit the CER; 22–27 (iv) integration of an in situ water purification process or seawater reverse osmosis system. 13,28,29 Apart from these means, considering the large E 0 difference between the saline CER/OER and alkaline OER, 18 it is likely that replacing complex saline anodic reactions with the thermodynamically favorable alkaline OER will also be an effective method to realize energy-saving and durable saline electrolysis.…”