Non-Precious Electrodes for Practical Alkaline Water Electrolysis

Abstract

Water electrolysis is a promising approach to hydrogen production from renewable energy sources. Alkaline water electrolyzers allow using non-noble and low-cost materials. An analysis of common assumptions and experimental conditions (low concentrations, low temperature, low current densities, and short-term experiments) found in the literature is reported. The steps to estimate the reaction overpotentials for hydrogen and oxygen reactions are reported and discussed. The results of some of the most investigated electrocatalysts, namely from the iron group elements (iron, nickel, and cobalt) and chromium are reported. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The experimental work is done involving the direct-current electrolysis of highly concentrated potassium hydroxide solutions at temperatures between 30 and 100 °C, which are closer to industrial applications than what is usually found in literature. Stable cell components and a good performance was achieved using Raney nickel as a cathode and stainless steel 316L as an anode by means of a monopolar cell at 75 °C, which ran for one month at 300 mA cm−2. Finally, the proposed catalysts showed a total kinetic overpotential of about 550 mV at 75 °C and 1 A cm−2.

Green Synthetic Fuels: Renewable Routes for the Conversion of Non-Fossil Feedstocks into Gaseous Fuels and Their End Uses

“…The ionic transfer and electric conductivity of the electrolyte strongly depend on type and concentration [168]. Typically, 20%-40%wt of KOH or NaOH is adopted, since a higher concentration reduces the water activity [169]. The partition of the product gases is ensured by a separator that generally is a porous diaphragm or a polymeric membrane.…”

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

“…However, their limited sources, high cost, and inferior stability at higher anodic potentials do not allow for large-scale usage [ 5 , 6 ]. Therefore, recently, there has been a huge effort to fabricate nanostructured oxide/hydroxide electrocatalysts based on earth-abundant elements [ 7 , 8 , 9 ]. Because of their eco-friendly properties and low cost, they have become interesting materials for different energy applications including batteries [ 10 ], supercapacitors [ 11 ], fuel cells [ 12 ], and alkaline water electrolyzers [ 13 , 14 ].…”

Stainless Steel as A Bi-Functional Electrocatalyst—A Top-Down Approach

“…In recent years, abundant transition metals such as nickel and iron have shown promising results for catalyzing the OER in alkaline medium with even lower overpotentials compared to noble-metals, thus increasing the efficiency [3,4,5]. On the HER side, there are many highly efficient abundant electrocatalysts in both alkaline and acidic media, such as transition metals phosphides, nickel and molybdenum-based compounds that could possibly replace platinum in the near future [3,6,7,8,9]. Additionally, in all electrochemical cells, electrons has to be transferred to and from the electrocatalysts for driving the reactions, and in alkaline electrolyzers current collectors of alkali resistant materials such as titanium, stainless steel, or nickel has to be used [10,11].…”

“…In this paper, we aim to improve the activity of ordinary stainless steel as an electrocatalyst for the water splitting reaction in alkaline medium using a top-down approach, without adding any separate electrocatalyst. We must mention that stainless steel recently have shown to be active as an electrocatalyst and in this study we focus to create a nanostructured surface to even improve the high activities measured [9,12,13]. To realize this, we use the fact that stainless steel contains several catalytically active elements such as iron, nickel and molybdenum in the bulk.…”

“…Remarkably, their activated stainless steel performed as an OER catalyst with benchmarking performance. To our knowledge, stainless steel has not shown high efficiency as an electrocatalyst for HER yet, and are inferior to other nickel based compounds [9]. By modifying the technique of H Schäfer et al, we were able to create a nanostructured Ni-Fe surface on the SSM electrode.…”