Recent Advances in Self-Supported Transition-Metal-Based Electrocatalysts for Seawater Oxidation

Abstract

Seawater electrolysis is a promising and sustainable technology for green hydrogen production. However, some disadvantages include sluggish kinetics, competitive chlorine evolution reaction at the anode, chloride ion corrosion, and surface poisoning, which has led to a decline in activity and durability and low oxygen evolution reaction (OER) selectivity of the anodic electrodes. Benefiting from the lower interface resistance, larger active surface, and superior stability, the self-supported nanoarrays have emerged as advanced catalysts compared to conventional powder catalysts. Self-supported catalysts have more advantages than powder catalysts, particularly in practical large-scale hydrogen production applications requiring high current density. During electrolysis, due to the influx of bubbles generated on the electrode surface, the powdered nanomaterial is peeled off easily, resulting in reduced catalytic activity and even frequent replacement of the catalyst. In contrast, self-supported nanoarray possessing strong adhesion between the active species and the substrates ensures good electronic conductivity and high mechanical stability, which is conducive to long-term use and recycling. This minireview summarizes the recent progress of selfsupported transition-metal-based catalysts for seawater oxidation, including (oxy)hydroxides, nitrides, phosphides, and chalcogenides, emphasizing the strategies in response to the corrosion and competitive reactions to ensure high activity and selectivity in OER processes. In general, constructing three-dimensional porous nanostructures with high porosity and roughness can enlarge the surface areas to expose more active sites for oxygen evolution, which is an efficient strategy for improving mass transfer and catalytic efficiency. Furthermore, the Cl − barrier layer on the surface of catalyst, particularly that with both catalytic activity and protection, can effectively inhibit the competitive oxidation and corrosion of Cl − , thereby delivering enhanced catalytic activity, selectivity, and stability of the catalysts. Moreover, developing super hydrophilic and hydrophobic surfaces is a promising strategy to increase the permeability of electrolytes and avoid the accumulation of large amounts of bubbles on the surface of the self-supported electrodes, thus promoting the effective utilization of active sites. Finally, perspectives and suggestions for future research in OER catalysts for seawater electrolysis are provided. In particular, the medium for seawater electrolysis should be transferred from simulated saline water to natural seawater. Considering the challenges faced in natural seawater splitting, in addition to designing and synthesizing self-supported catalysts with high activities, selectivity, and stability, developing simple and low-cost natural seawater pretreatment

Recent advances of bifunctional electrocatalysts and electrolyzers for overall seawater splitting

“…Several recent reviews have discussed the electrocatalysts for seawater splitting from different perspectives, mainly single-function OER catalysts 28,29 and design strategies of electrocatalysts. 30,31 Recently, our team completed a review covering both lab-scale fundamental research and pilot-scale reactor levels, as well as future trends in the field of seawater electrolysis.…”

In Situ Reconstructed Layered Double Hydroxides via MOF Engineering and Ru Doping for Decoupled Acidic Water Oxidation Enhancement

“…These basic sites within LDHs serve as unique active sites for metal atoms, enhancing the material’s electronic behavior and facilitating successful OER reactions . Co, Fe, and Ni derivatives are not only employed in water electrolysis, but significant efforts are also being directed toward their application in seawater and urea electrolysis. − The NiFe and NiCo-LDH composite materials, characterized by their distinctive LDH geometrical structure and substantial active surface area, possess an abundance of active sites, making them outstanding catalyst materials with superior electrocatalytic properties.…”

Boosting Alkaline Seawater Oxidation of CoFe‐layered Double Hydroxide Nanosheet Array by Cr Doping

“…[13][14][15][16][17][18][19][20][21][22] Consequently, a critical task is to explore electrocatalysts exhibiting high selectivity and tolerance for seawater oxidation Transition-metal compound catalysts have garnered significant interest toward seawater oxidation. [15][16][17][18][19][20][21][22][23][24][25][26][27][28] Among these, CoFe-based materials, particularly CoFe layered double hydroxide (LDH), exhibits OER activity for seawater oxidation. [29] CoFe-LDH, however, faces limitations due to its inadequate electrical conductivity and susceptibility to chloride corrosion.…”