Superhydrophilic/Superaerophobic Hierarchical NiP₂@MoO₂/Co(Ni)MoO₄ Core–Shell Array Electrocatalysts for Efficient Hydrogen Production at Large Current Densities

Abstract

Rationally constructing low-cost, high-efficiency, and durable electrocatalysts toward the hydrogen evolution reaction at large current densities is imperative for water splitting, especially for large-scale industrial applications. Herein, a hierarchical core–shell NiP2@MoO2/Co­(Ni)­MoO4 cuboid array electrode with superhydrophilic/superaerophobic properties is successfully fabricated and the formation mechanism of the core–shell structure is systematically investigated. Through an in situ partially converted gas–solid reaction during the phosphating process, Ni and Co elements are leached and rearranged to form NiP2 particles and amorphous CoO as the shell layer and the inner undecomposed Co­(Ni)­MoO4 crystals serve as the core layer. Because of its seamless core–shell structure and superhydrophilicity/superaerophobicity of hierarchical cuboid arrays, NiP2@MoO2/Co­(Ni)­MoO4 exhibits superior HER activity in 1 M KOH with only an overpotential of 297 mV to deliver 1000 mA cm–2 and can work steadily for 650 h at 200 mA cm–2. Remarkably, when coupled with NiFe LDH for overall water splitting, it can drive an AA battery with an ultralow cell voltage of 1.49 V to deliver 10 mA cm–2. This work sheds new light on designing large-current-density efficient HER electrocatalysts for large-scale industrial applications.

Key components and design strategy of the membrane electrode assembly for alkaline water electrolysis

“…Thus, it is crucial to design the CL architecture in such a way as to decrease gas bubble adhesion behavior, facilitate electrolyte diffusion, and reduce reaction resistance, thus maintaining the catalytic ability of CLs. 329,330 Therefore, great efforts have been devoted to regulating the composition and micro-/nanostructure of the electrode surface with superhydrophilicity. In a typical example, Jiang et al prepared a CoS x -Ni 3 S 2 nanosheet array on Ni foams.…”

Engineered Superhydrophilic/Superaerophobic Catalyst: Two-Dimensional Co(OH)2–CeO2 Nanosheets Supported on Three-Dimensional Co Dendrites for Overall Water Splitting

“…Recently, 3D hierarchical metal arrays have been researched for water electrolysis. , The unique fractal structure can enlarge the contact surface with the electrolyte, which facilitates the mass transport and bubble diffusion . In addition, the micro/nanostructures on 3D arrays have a positive effect on modifying the surface wettability of electrodes . Research shows that superhydrophilic/superaerophobic interfaces are ideal, which facilitate full contact between the electrolyte and electrode and bubbles leave. , Therefore, accelerating the mass transfer at the gas–liquid–solid reaction interface is a significant but less concerned approach in current research studies compared to improving the intrinsic activity of materials.…”

“…In addition, the micro/nanostructures on 3D arrays have a positive effect on modifying the surface wettability of electrodes . Research shows that superhydrophilic/superaerophobic interfaces are ideal, which facilitate full contact between the electrolyte and electrode and bubbles leave. , Therefore, accelerating the mass transfer at the gas–liquid–solid reaction interface is a significant but less concerned approach in current research studies compared to improving the intrinsic activity of materials. 3D cobalt dendrites exhibit excellent electrical conductivity and plentiful porous channels, which is conducive to the release of gas bubbles.…”

Interface engineering of a Ni9S8/MoS2/Ni3S2 heterostructure to boost biomass upgrading coupled with the hydrogen evolution reaction at large current densities

“…1 To date, many promising strategies such as electro-chemical water splitting have been applied to obtain sustainable H 2 production. [2][3][4] However, due to the high energy requirement, its widespread practical application has been severely constrained by the significant thermodynamic overpotentials of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) during the process of water splitting. [5][6][7] Consequently, it is very important to substitute the OER with high-value oxidation processes that can effectively reduce energy consumption for H 2 production, meanwhile, coupled with achieving important fine chemical intermediate materials.…”