Electrolyzer Electrode Material Selection Guide

Woven nickel mesh (30-40 mesh, Ni201) is the correct catalyst substrate. Knitted nickel mesh (660-850 g/m2, Ni201) is the correct porous transport layer. Nickel wire (Ni201 annealed) is the correct current collector. One material cannot solve all three positions. Using the wrong material at any position creates a failure mode that limits the entire stack lifetime — regardless of how good the catalyst, membrane, or balance of plant is.

TL;DR — 3 positions, 3 materials: woven Ni201 mesh (catalyst substrate, 30-40 mesh), knitted Ni201 mesh (PTL, 660-850 g/m2, 90-95% porosity), Ni201 wire (current collector, annealed, 0.5-2.0 mm). Ni foam collapses under compression. SS 316L fails via SCC in hot KOH. Specify by position, not by product.

Three Electrode Positions, Three Material Requirements

1. Catalyst Support Substrate. Requires uniform aperture distribution for consistent current density, high surface adhesion for Raney nickel catalyst coating, and a burr-free surface finish to protect the Zirfon or asbestos diaphragm from mechanical puncture. Recommended: Woven nickel mesh — 30-40 mesh per inch, plain weave, 0.25-0.30 mm wire diameter, Ni201 grade, electropolished finish. Ordered aperture geometry ensures every unit cell of the electrode has identical electrical path length and catalyst loading. ASTM B456 and ISO 9044 compliant.

2. Porous Transport Layer (PTL). Requires elastic compressibility to maintain electrical contact under 5-15 bar stack clamping force, volumetric porosity above 85% for two-phase electrolyte-gas flow, and recovery from repeated compression cycles over the stack lifetime (60,000+ hours). Recommended: Knitted nickel mesh — 660-850 g/m2 packing density, single jersey knit, 90-95% porosity, Ni201 grade. The three-dimensional loop structure functions as an elastic spring. Interlock (double-knit) variant at 850-1150 g/m2 for large-area stacks above 1 m2 active area where PTL collapse is the primary failure risk.

3. Current Collector / Lead Wire. Requires electrical conductivity of 14-18% IACS to carry DC current from the busbar to individual electrode elements, mechanical ductility of minimum 30% elongation for forming and welding, and sustained corrosion resistance in 30% KOH at 80-90 C. Recommended: Nickel wire — Ni201 grade, annealed temper, 0.5-2.0 mm diameter for internal wiring. Ni201 limits carbon to 0.02% maximum, preventing grain-boundary carbide precipitation (Ni3C) that causes intergranular corrosion in standard Ni200 (0.15% C) after 20,000+ hours. ASTM B162 compliant.

Head-to-Head Comparison

Criterion	Woven Ni Mesh	Knitted Ni Mesh	Ni Foam (80-110 PPI)	SS 316L
Porosity	35-55% geometric	85-98% volumetric	85-98% volumetric	N/A (solid plate)
Compressibility	Rigid	Elastic spring-back	Plastic collapse	Rigid
Current Uniformity	Excellent (ordered geometry)	Good (elastic contact)	Poor (random structure)	Good (solid)
KOH Corrosion at 85 C	Passive (stable Ni(OH)2 film)	Passive	Passive	SCC + Fe leaching into electrolyte
Dimensional Stability	Excellent (50,000+ hrs)	Good under compression	Poor (pore collapse)	Excellent
Industrial Track Record	50,000+ hrs proven	30,000+ hrs proven	Lab-scale only	Not recommended for KOH
Cost (relative)	$$	$$	$$$	$
Best For	Catalyst substrate	PTL / spring layer	R&D cells only	External hardware only

Bottom line: Specify by position. The catalyst substrate, PTL, and current collector are three different engineering problems. Woven Ni201 mesh + knitted Ni201 mesh + Ni201 wire is the matched electrode material set for alkaline electrolyzer stacks targeting 60,000+ hour lifetimes.