Amorphous Nickel-Based Thin Film As a Janus Electrocatalyst for Water Splitting

Abstract

Hydrogen generated by water splitting provides a renewable energy source, but development of materials with efficient electrocatalytic water splitting capability is challenging. Thin-film electrocatalytic material (H 2 −NiCat) with robust water reduction properties, which can be readily prepared by a reduction-induced electrodeposition method from nickel salts in a borate-buffered electrolyte (pH 9.2), is reported. The material consists of nanoparticles with nickel oxide or hydroxide species located at the surface and metallic nickel in the bulk. The catalyst mediates H 2 evolution in a near-neutral aqueous buffer at low overpotential. The catalyst requires a subsequent oxidative pretreatment in order to attain a well-defined hydrogen evolution reaction (HER) activity, and the 1.5 h anodized catalyst film exhibits a HER current density of about 1.50 mA cm −2 at 0.452 V overpotential over a period of 24 h with no observable corrosion. In addition, it can be converted by anodic equilibration into an amorphous Ni-based oxide film (O 2 −NiCat) to catalyze O 2 evolution, and the switch between the two catalytic forms is fully reversible. The robust, bifunctional, switchable, and noble-metal-free catalytic material has immense potential in artificial solar water-splitting devices.

Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

“…[ 47 ] NiCat showed HER activity of −1.52 mA cm −2 at η = 452 mV and OER activity of +0.6 mA cm −2 at η = 618 mV. [ 48 ] In these materials, the potential controlled transformation between different catalytic species and morphologies was shown to be responsible for the bi-functional activity. H 2 -CoCat is reported to contain metallic cobalt active sites in an oxo-hydroxy-phosphate matrix, whereas O 2 -CoCat, more widely known as CoP i is a cobalt oxide.…”

“…[ 27,47 ] The analogous NiCat is similar replacing cobalt and phosphate with nickel and borate. [ 48 ] Unlike these materials, however, here the two catalytic phases are not likely to exchange through solution via a dissolution-deposition mechanism, but instead may convert in the solid state. This is supported by the lack of major morphological change before and after catalysis as observed by SEM ( Figure S8, Supporting Information) and further while CoCat and NiCat are metastable with respect to dissolution under open-circuit potential, the iron-based fi lms reported herein are stable in their electrolyte solution.…”

Ni2P as a Janus catalyst for water splitting: the oxygen evolution activity of Ni2P nanoparticles

“…Analogous behavior was reported by Wu and co-workers for amorphous Ni oxo hydroxo film in pH 9.2 borate buffer. 8 Grätzel and co-workers showed that NiFe layered double hydroxide is a bifunctional catalyst for water splitting in alkaline conditions, and applied it for water photolysis in conjunction with a perovskite tandem solar cell. 10 Herein, we…”

First row transition metal catalysts for solar-driven water oxidation produced by electrodeposition

“…Bifunctional catalysts able to perform both the OER and HER have been reported using electrodeposited nickel oxides. Both Wu 47 and Du 48 used cathodic potentials and borate solutions containing Ni(II)…”