Abstract
Hydrogen production by water splitting using nanomaterials as electrocatalysts is a promising route enabling replacement of fossil fuels by renewable energy sources. In particular, the development of inexpensive non-noble metal-based catalysts is necessary in order to replace currently used expensive Pt-based catalysts. We report a detailed impedance spectroscopy study of Ni-Mo and Ni-Fe based electrocatalytic materials deposited onto porous and compact substrates with different conductivities. The results were interpreted by a critical comparison with equivalent circuit models. The reaction resistance displays a strong dependence on potential and a lower substrate dependence. The impedance behaviour can also provide information on the dominating reaction mechanism. An optimized Ni-Fe based catalyst showed very promising properties for applications in water electrolysis.
Highlights
Hydrogen is a promising alternative to fossil fuels and can be used as energy storage
We focus on the impedance spectroscopy technique and present impedance spectra pertaining to the hydrogen evolution reaction (HER) for two transition metal-based electrocatalysts prepared by different methods
Depositions were done in Ar gas at 30 mTorr pressure, using powers of 80 W and 180 W for Ni and Mo, respectively, onto the following substrates: Ni foam, Ni foil, Carbon cloth (C–cloth), indium tin oxide (ITO) coated glass and fluorine doped tin oxide (FTO) coated glass
Summary
Hydrogen is a promising alternative to fossil fuels and can be used as energy storage. It is useful for storing electricity from intermittent renewable sources, which later can be used to produce heat, or alternatively electricity on-demand via fuel cells [1]. Used highly effective Pt- and Ir-based electrocatalysts need to be replaced by less expensive and more earth-abundant alternatives and here transition metal alloys, oxides/hydroxides or other transition metal compounds are of prime interest [3,4]. The HER is quite well understood in both acidic and alkaline solutions. It is summarized by the following basic reaction steps [5,6,7]: MM + HH2OO + ee− ↔ MM − HH + OOOO− MM − HH + HH2OO + ee− ↔ HH2 + OOOO− + MM MM − HH + MM − HH ↔ HH2 + 2MM (Volmer step) (1)
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