Selective Electrochemical Alkaline Seawater Oxidation Catalyzed by Cobalt Carbonate Hydroxide Nanorod Arrays with Sequential Proton-Electron Transfer Properties

Abstract

Seawater oxygen evolution is one of the promising energy conversion technologies for large-scale renewable energy storage. It requires efficient catalysts to accelerate the oxygen evolution reaction (OER) for sustained water oxidation, avoiding chlorine evolution under acidic conditions or hypochlorite formation in alkaline solutions. Conventional metal oxide-based OER catalysts follow the adsorbate evolution mechanism that involves concerted proton-electron transfer steps at the active sites. Thus, on the scale of reversible hydrogen electrode, their catalytic activity is independent of the pH of electrolytes. In the present study, nanostructured cobalt carbonate hydroxide (CoCH) with sequential proton-electron transfer properties was tested as a catalyst for seawater oxygen evolution. CoCH exhibited pH-dependent water oxidation activities, thereby providing larger potential and current operating windows for selective water oxidation compared to the catalysts with pH-independent OER activities. The operating window can be further expanded by increasing the pH of the electrolyte.

Structural Anisotropy Determining the Oxygen Evolution Mechanism of Strongly Correlated Perovskite Nickelate Electrocatalyst

“…In general, the stability of the O* and OO*(V O ) intermediates, which are the key reaction intermediates of the AEM and LOM, respectively, would determine the favorable OER mechanism. 44,45 Specifically, the V O formation step plays an important role in the formation of OO*(V O ) in the LOM, which has been verified by a previous study. 43,46 Further, oxygen vacancy concentration was reported to be an effective parameter in lowing the OER overpotential.…”

“…In general, the stability of the O* and O O*­(V O ) intermediates, which are the key reaction intermediates of the AEM and LOM, respectively, would determine the favorable OER mechanism. , Specifically, the V O formation step plays an important role in the formation of O O*­(V O ) in the LOM, which has been verified by a previous study. , Further, oxygen vacancy concentration was reported to be an effective parameter in lowing the OER overpotential. − The lower formation energy of V O indicates the easier participation of lattice oxygen in the OER, which was also declared from the results of NNO with different orientation surfaces. Following this line of thinking, the V O formation free energy was calculated with the consideration of different surface orientations.…”

Partial Sulfidation Strategy to NiFe‐LDH@FeNi2S4 Heterostructure Enable High‐Performance Water/Seawater Oxidation

“…Direct seawater electrolysis can solve severe issues of scarce water supply and high freshwater demand by utilizing fluctuant sustainable energies, particularly in some coastal arid zones. [9][10][11][12] One of the biggest challenges for seawater electrolysis stems from the oxidation of chloride anions including the chlorine evolution reaction (CER) in an acidic electrolyte and the formation of hypochlorite (ClO − ) in an alkaline media, both of which will compete with the OER. [11,[13][14][15] At high pH (>7.5), theoretical overpotentials for the ClO − formation, and OER are linearly related to the pH value with the same slope.…”

Strategies of Anode Design for Seawater Electrolysis: Recent Development and Future Perspective

“…In seawater splitting, the HER and OER are associated with local pH variation at the electrode and regarded as a critical issue. [ 33 ] During electrolysis, there has been a continuous reduction in pH at anode due to OH − oxidation and an increment in pH at cathode due to H + reduction. Studies revealed that this pH fluctuation is in 5–9 pH units and triggers severe catalyst degradation even at a small geometric activity.…”

“…Li et al synthesized carbon fiber‐supported cobalt carbonate hydroxide (Co CH@CFP) and compared its selectivity and activity with Ni–Fe layered double hydroxide (LDH) for seawater oxidation. [ 33 ] The Co CH@CFP exhibited high selectivity and activity for OER compared with Ni–Fe LDH. This high performance was explained by the acid–base properties of the catalyst surface determined through the pH shift method.…”