HydroXpandHandbook

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Cell assembly overview

HXP-an · HXP-ca · updated 2026-10-05

From received electrodes to a test cell and its first measurement, the most common failure (gaskets), and what you do not need to do.

The route from received electrodes to a test cell and its first measurement, on one page. Values such as clamping torque and the measurement sequence are in the electrode operation note; this chapter covers the order of work and the decisions people most often get wrong.

  • LayoutAnode below · cathode above
  • Pre-treatment · activationNone
  • Clamping valuesDepend on your hardware
How to read this chapter

First timeLook at the sequence table in the first section, then follow the link on each row for the values. Read the gasket section before you assemble.

Done this beforeGo back to the gasket section. Most leaks and performance problems start there.

On this pageThe sequence at a glance

The sequence at a glance#

StepWhat to doDetails
1. InspectCheck for creases, tears, catalyst delamination and crushed edges. Do not build a cell with a damaged sheetReceiving · inspection
2. CutIf needed, cut to your active area: on a flat backing, in one pass, then clear the dustFormats · made to order
3. Stack upAnode at the bottom, cathode on top. Lay HXP-ca with its catalyst-layer face towards the membrane (HXP-an has no orientation). The electrolyte circulates on the anode side. Insulate the end plates with a PTFE sheetNote · cell assembly
4. GasketsSettle the thickness by clamping trials. See the next sectionThis chapter · gaskets
5. ClampTighten to the assembly guide for your cell hardware. Do not carry stack clamping conditions over to a cellNote · cell assembly
6. Electrolyte and heat-upCirculate 0.1 M KOH and bring it to 50 °C. Confirm the temperature actually reached, not the setpointNote · operating conditions
7. Start upThere is no separate activation step. Bring it to rated current and start measuring once the voltage has settledNote · start-up
8. MeasureFollow the measurement sequence, and match the conditions before comparing with the datasheetChecking performance and reading data
Exploded view of a test cell, layer by layer. From the bottom: end plate with a PTFE sheet, anode-side cell hardware where the electrolyte enters and leaves, the HXP-an anode (nickel foam, either side up) with a gasket on each side, the anion exchange membrane, the HXP-ca cathode with a gasket on each side (catalyst face to the membrane, carbon paper face up), cathode-side cell hardware where hydrogen leaves, and an end plate with a PTFE sheet. Bolts outside clamp the stack. Step 3 is stacking from the bottom up (anode below, cathode above), step 4 the gaskets (not chosen to the electrode thickness; settled by clamping trials), step 5 clamping (to your cell hardware's guide, not the stack clamping conditions).
Figure 4-1 Stacking a test cell. Numbers match the steps in the table above. Schematic; flow fields and ports differ between cell hardware.

Gaskets: the most common failure#

When a cell leaks or underperforms, the gasket is more often the cause than the electrode. Hold to two things.

Seating
O-rings ride out of their seat and the MEA gasket shrinks inwards. Push them back into place after seating.
Thickness
Do not simply match it to the electrode thickness. A nickel-foam anode compresses a great deal when clamped, by an amount that depends on the material. Try a few thicknesses, clamp each, and settle on one by checking for leaks and for cell performance.

What you do not need to do#

  • Pre-treatment. Electrodes ship cleaned and dried.
  • Activation. There is no separate activation step; bring the cell to temperature and run at rated current.

What this chapter is based on

Resource library →

TroubleshootingDamage on arrival, a leaking cell, numbers that differ from the datasheet: what to check first, and what to send us.
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