Abstract
For a hydrogen economy to be viable, clean and economical hydrogen production methods are vital. Electrolysis of water is a promising hydrogen production technique with zero emissions, but suffer from relatively high production costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent electrical connection to the bulk structure. At ambient temperature, the activated stainless steel electrodes produce 10 mA/cm2 at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes.
Highlights
Hydrogen has the highest gravimetric energy density of all known substances [1], where the chemically stored energy can be extracted as electricity in fuel cells with zero CO2 emission and water as the only output [2]
The activated stainless steel electrodes produce 10 mA/cm2 at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts
Water is split into hydrogen and oxygen by two half-cell reactions, i.e., the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER)
Summary
Hydrogen has the highest gravimetric energy density of all known substances [1], where the chemically stored energy can be extracted as electricity in fuel cells with zero CO2 emission and water as the only output [2]. Hydrogen production by electrolysis of water is a promising zero emission technique, but suffers from relatively low efficiency and the use of scarce noble metals in the process [2]. Commercial electrocatalysts are today made of scarce noble-metals such as iridium or ruthenium for the OER, and for the HER platinum-based electrocatalysts are the most efficient [2,3,4] For this technique to be cost-effective, finding earth-abundant materials that catalyze the water splitting reactions with high-efficiency is crucial, especially for the OER that suffer from the highest overpotential of the two reactions
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