Phosphate Group Dependent Metallic Co(OH)₂ toward Hydrogen Evolution in Alkali for the Industrial Current Density

Abstract

Developing efficient and low-cost electrocatalysts is critical for hydrogen evolution by water splitting. Nonsubjective reconstruction is one of the main issues that induces difficulty to develop and understand the well-defined structure during the electrocatalysis. By studying the anion-exchange between phosphate and hydroxide, cobalt hydroxide nanosheets incorporated with phosphate inherited from cobalt phosphate are obtained, which provides a new case of metallic transition metal hydroxide. Benefiting from more exposed active sites, effective electron transport, and optimized electronic structure, the residual phosphate in two-dimensional Co(OH) 2 gives rise to significant improvement in alkaline hydrogen evolution. Particularly, it can survive at 1600 mA cm −2 and maintain stability over 100 h under industrial conditions (6 M KOH at 60 °C). Density functional theory calculations and the confirmatory experiments of reverse anion-exchange from Co(OH) 2 are investigated to confirm the successful engineering of metallic character and electronic structure. This work provides a facile modification of practical electrodes with phosphate groups for industrial water electrolysis as well as gaining insights into the reconstruction of cobalt-based electrocatalysts in alkali to become an effective catalyst.

Research status, opportunities, and challenges of cobalt phosphate based materials as OER electrocatalysts

“…Nevertheless, the crystal structure of phosphate was not evidently changed by the introduction of phosphate. 104…”

“…Nevertheless, the crystal structure of phosphate was not evidently changed by the introduction of phosphate. 104 The reconstruction process of CoPi catalysts during the OER process has a significant impact on the catalytic activity, which can be observed through the following key aspects: (a) Surface reconstruction: during the OER process, the CoPi catalyst undergoes surface reconstruction, involving various changes such as changes in oxidation state, rearrangement of chemical bonds, and restructuring of the lattice structure. 105 In the OER process, the surface of CoPi undergoes oxidation, leading to the rearrangement of atoms and reconstruction of the lattice.…”

Strong Electron Interaction at the Amorphous/Crystalline Interface Enables Advanced Oxygen Evolution Reaction

“…Electrochemical water splitting coupled with a renewable energy source for preparing green hydrogen provides great potential to achieve carbon neutrality. , Two half-reactions of oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode are included. − In comparison to the one-electron HER process, the completed four-electron reaction process of OER hinders the efficiency of overall water splitting. − Therefore, the development of high-performance OER catalysts is a key aspect of water electrolysis. − Different from the water electrolysis in acid, that in alkaline or neutral conditions exhibits a lower requirement for anticorrosion. − For example, both of them can be driven by nonprecious metal-based electrocatalysts such as Fe, Co, Ni, etc. − Though they have an advantage over precious metal catalysts in terms of price, their high overpotential, poor electrical conductivity, and slow electron-transfer process are still far from practical application. − Moreover, neutral electrolysis is mostly based on phosphate-buffered solution (PBS), which generally produces low current densities and requires extra energy for the water dissociation process due to the low OH – concentration. , Therefore, the development of basic and neutral OER catalysts faces serious challenges. , …”

Unveiling the Effect of Organic Sulfur Sources on Synthesized MoS2 Phases and Electrocatalytic Hydrogen Evolution Performances

“…To realize green hydrogen, the hydrogen must be from water through photocatalysis or electrocatalysis with electricity produced by new energy technologies, such as solar cells, wind, water, and so on . Electrocatalytic hydrogen evolution reaction (HER) from water has therefore attracted extensive attention. − The efficiency of electrocatalytic HER is mainly determined by catalysts. − To date, Pt-based materials have the best electrocatalytic activity toward HER. However, the scarcity leads to high cost for using Pt as a HER catalyst and greatly hinders large-scale commercial applications .…”