ELECTRODE SPECIFICATION
HER OVERPOTENTIAL80 mV HER Overpotential at 100 mA/cm2
Measured on our bifunctional NiCo electrode in 30 wt% KOH at 100 mA/cm2 without any IR correction. The same coated electrode also serves as the OER anode at 260 mV overpotential.
HER OVERPOTENTIAL
TESTBEDThis spec
HER OVERPOTENTIAL
HER overpotential
@ 100 mA/cm² (no IR)
OER overpotential
@ 100 mA/cm² (no IR)
Cell @ 0.5 A/cm² / 60 °C
91.4% efficiency
1000-hour drift
@ 0.5 A/cm² / 40 °C
What HER overpotential measures
The hydrogen evolution reaction (HER) is the cathode-side half-reaction in water electrolysis: water plus electrons becomes hydrogen plus hydroxide. The overpotential is the extra voltage above the thermodynamic minimum required to drive HER at a given current density. Lower HER overpotential at a given current means less of the input electricity is lost as voltage drop across the cathode catalyst.
Our bifunctional NiCo electrode is a bi-metallic transition-metal catalyst deposited on Ni foam (100 to 1000 cm2) by electroless deposition. At 100 mA/cm2 in 30 wt% KOH, the HER overpotential is 80 mV. This measurement was taken without any IR correction.
- Reaction: water + electrons -> hydrogen + hydroxide (cathode side)
- Overpotential: 80 mV at 100 mA/cm2
- Electrolyte: 30 wt% KOH
- No IR correction applied
- Same electrode also serves as OER anode (bifunctional)
Why no IR correction matters
IR correction is a post-measurement step that subtracts the ohmic loss in the cell from the recorded voltage to isolate the "true" catalyst overpotential. It is sometimes useful for fundamental catalyst comparison but it overstates real-world cell performance because, in an actual electrolyzer, the ohmic loss is a real cost that has to be paid.
The 80 mV HER overpotential on our bifunctional NiCo electrode is reported as measured, without the IR correction. The number reflects what the electrode contributes inside the test cell at 100 mA/cm2 in 30 wt% KOH.
How HER overpotential rolls up to cell voltage
In a full AEM cell with our bifunctional NiCo electrode on both sides and a commercial Zirfon separator (500 um) at 30 wt% KOH and zero-gap assembly, the cell reaches 0.5 A/cm2 at 1.81 V at room temperature (82% energy efficiency) and 1.62 V at 60 deg C (91.4%). The HER contribution at the cathode is one component of that voltage; the OER contribution at the anode, the ionic resistance of the separator, and the bulk electrolyte resistance are the others.
The same cell measures 2.05 V at 1.0 A/cm2 at room temperature and 1.79 V at 1.0 A/cm2 at 60 deg C. The 60 deg C polarization curve sits well below the room-temperature curve across the full current-density range.
Stability of the HER side over 1000 hours
During the continuous 1000-hour run at 0.5 A/cm2 and 40 deg C in 30 wt% KOH with the bifunctional NiCo electrode on both sides and a commercial Zirfon separator, the cell voltage drifted by 21 uV/hr. Before/after linear-sweep polarization curves differ by 30 mV at 0.5 A/cm2.
Because the same electrode formulation serves both sides, the 21 uV/hr cell-level drift is the integrated behavior of both the HER cathode and the OER anode across 1000 hours of continuous operation.
How to evaluate HER on your own cell
A typical evaluation begins at 5 cm2 (matching the size used in our published test cell). The electrode is supplied on Ni foam in the 100 to 1000 cm2 size range, and the HER half-cell measurement can be reproduced in any three-electrode setup with a saturated calomel or Hg/HgO reference in 30 wt% KOH. The 80 mV value at 100 mA/cm2 is the published reference point that third-party measurements can be compared against.
Where this specification matters
Industrial applications where her overpotential 80 mv at 100 ma/cm2 is a primary qualification metric.
Frequently asked questions
What is the HER overpotential of this electrode?
80 mV at 100 mA/cm² in 30 wt% KOH, measured without IR correction. This is the published reference value for our bifunctional NiCo electrode.
How is her overpotential 80 mv at 100 ma/cm2 measured?
All published values were measured in a 5 cm² AEM cell with our bifunctional NiCo electrode on both sides, 30 wt% KOH electrolyte, zero-gap assembly, and a commercial Zirfon separator (500 µm) as the membrane reference. Overpotentials are reported without IR correction.
Can I reproduce this number on my own cell?
Yes. Bench-scale 5 cm² coupons matching the size used in our published AEM test cell are available. Reproducing the cell conditions (30 wt% KOH, zero-gap, commercial Zirfon separator, bifunctional NiCo electrode on both sides) lets a customer team confirm the published number directly.
What substrate sizes can I order?
We produce the bifunctional NiCo electrode on Ni foam in the 100 to 1000 cm² size range. Bench-scale coupons and pilot-scale electrodes both ship from this same product line. Specific sizes can be discussed for OEM stack integration.
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