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Energy harvesting from solar and water has created ripples in materials energy research for the last several decades, complemented by the rise of Hydrogen as a clean fuel. Among these, water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. In fact, solar water splitting is one of the most promising method to produce Hydrogen without depleting fossil-fuel based natural resources. However, the efficiency and practical feasibility of water electrolysis is limited by the anodic oxygen evolution reaction (OER), which is a kinetically sluggish, electron-intensive uphill reaction. A slow OER process also slows the other half- cell reaction, i.e. the hydrogen evolution reaction (HER) at the cathode. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing solar water splitting. In the Nath group we have focused on transition metal chalcogenides as efficient OER electrocatalysts. We have proposed the idea that these chalcogenides, specifically, selenides and tellurides will show much better OER catalytic activity due to increasing covalency around the catalytically active transition metal site, compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chem. potential around the transition metal center, [e.g. lowering the Ni 2+ --> Ni 3+ oxidn. potential in Ni-based catalysts where Ni 3+ is the actually catalytically active species]. Based on such hypothesis, we have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm 2 [Ni 3 Se 2 - 200 - 290 mV; Co 7 Se 8 - 260 mV; FeNi 2 Se 4 -NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe 2 Se 4 - 210 mV; CoNi 2 Se 4 - 190 mV; Ni 3 Te 2 - 180 mV].
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This content will become publicly available on February 2, 2026
Impacts of Dissolved Iron on Alkaline Water Electrolysis Cells
Dissolved iron (Fe) species are a pre-requisite for the most active catalyst sites for the oxygen evolution reaction in alkaline electrolytes, but the overall effects of dissolved Fe on energy- efficient advanced alkaline water electrolysis cells remain unclear. Here, we systematically control the concentration of Fe in a model zero-gap alkaline water electrolyzer to understand the interactions between Fe and high surface area catalyst coatings. Cells employing a platinum-group- metal-containing cathode and a high surface area, mixed-metal-oxide anode yielded an optimum voltage efficiency at elevated temperatures and in the presence of 6 ppm Fe, which reduced the cell voltage by ~100 mV compared to rigorously Fe-free electrolytes. Increasing concentrations of Fe led to a systematic increase in anode activity towards the oxygen evolution reaction and a reduction in the electrochemically active surface area at both the anode and cathode. Metallic Fe was not observed to electrodeposit at cathodes which operate at overpotentials ≤ 120 mV, but dissolved Fe does reduce the apparent number density of sites available for hydride adsorption. These findings suggest that the energy efficiency of advanced alkaline water electrolysis systems can be improved by managing the Fe concentration in recirculating KOH electrolytes.
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- Award ID(s):
- 2400195
- PAR ID:
- 10594533
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Catalysis
- Volume:
- 15
- Issue:
- 4
- ISSN:
- 2155-5435
- Page Range / eLocation ID:
- 2847 to 2856
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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