The Influence of the Electrodeposition Parameters on the Properties of Mn-Co-Based Nanofilms as Anode Materials for Alkaline Electrolysers

Abstract

In this work, the influence of the synthesis conditions on the structure, morphology, and electrocatalytic performance for the oxygen evolution reaction (OER) of Mn-Co-based films is studied. For this purpose, Mn-Co nanofilm is electrochemically synthesised in a one-step process on nickel foam in the presence of metal nitrates without any additives. The possible mechanism of the synthesis is proposed. The morphology and structure of the catalysts are studied by various techniques including scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The analyses show that the as-deposited catalysts consist mainly of oxides/hydroxides and/or (oxy)hydroxides based on Mn2+, Co2+, and Co3+. The alkaline post-treatment of the film results in the formation of Mn-Co (oxy)hydroxides and crystalline Co(OH)2 with a β-phase hexagonal platelet-like shape structure, indicating a layered double hydroxide structure, desirable for the OER. Electrochemical studies show that the catalytic performance of Mn-Co was dependent on the concentration of Mn versus Co in the synthesis solution and on the deposition charge. The optimised Mn-Co/Ni foam is characterised by a specific surface area of 10.5 m2·g−1, a pore volume of 0.0042 cm3·g−1, and high electrochemical stability with an overpotential deviation around 330–340 mV at 10 mA·cm−2geo for 70 h.

The Effect of Cobalt Incorporation into Nickel–Iron Oxide/(oxy)hydroxide Catalyst on Electrocatalytic Performance Toward Oxygen Evolution Reaction

“…The mechanism of the electrodeposition of the catalysts based on earth-abundant metal transition elements has already been described in the previous work for Mn-Co-based oxides/ hydroxides/(oxy)hydroxides. [13] The applied deposition potential resulted in the reaction of the NO 3 À nitrates and the hydrogen evolution, which led to the increase in the OH À hydroxide ions in the synthesis solution. The OH À ions started to react with the metallic elements, i.e., cobalt, nickel, iron, and formed metallic hydroxides in the second and/or third oxidation state forming hydroxides and the (oxy)hydroxides form of the catalysts.…”

Evaluation of electrosynthesized reduced graphene oxide–Ni/Fe/Co-based (oxy)hydroxide catalysts towards the oxygen evolution reaction

“…Combining a graphene material with Ni-, Fe- and/or Co-based oxides/hydroxides with high chemical reactivity provides both an effective electron pathway through the catalyst [ 20 ] and high specific surface area [ 21 ], which is desirable for the OER process [ 13 ]. The overall electrocatalytic performance of the hybrid electrode can also be improved by choosing a conductive and/or high surface area substrate, such as porous nickel foam [ 22 – 23 ].…”

Evaluation of electrosynthesized reduced graphene oxide - Ni-, Fe-, Co-based (oxy)hydroxide catalysts toward oxygen evolution reaction

“…Combining a 3 graphene material with Ni-, Fe-and/or Co-based oxides/hydroxides with high chemical reactivity provides both an effective electron pathway through the catalyst [20] and high specific surface area [21], which is desirable for the OER process [13]. The overall electrocatalytic performance of the hybrid electrode can also be supported by choosing a conductive and/or high surface area substrate, such as porous nickel foam [22,23].…”