Raney Nickel Catalyst — Complete Technical Guide

Raney nickel is a porous nickel catalyst with 50-100 m2/g BET surface area, produced by leaching aluminum from a Ni-Al alloy in NaOH. It is the standard hydrogen evolution reaction (HER) catalyst in every industrial alkaline water electrolyzer. Its dominance is structural: no other cost-competitive material simultaneously delivers high intrinsic HER activity in alkaline media, electrical continuity through the nickel skeleton, and compatibility with 25-30% KOH at 80-90 C.

TL;DR — Raney nickel (Ra-Ni): 50-100 m2/g BET surface area, 1000x solid Ni. Produced by NaOH leaching of Ni-Al alloy. Spray-coated onto woven Ni201 mesh (30-40 mesh, 0.25 mm wire). Pyrophoric when dry — store under water. Standard HER catalyst for AWE.

How Raney Nickel Is Made: Three Stages

1. Alloy Casting and Crushing. High-purity nickel (min 99.5%) and aluminum are induction-melted under argon at 1500 C and cast into ingots. A 50:50 wt% Ni-Al composition produces a mixture of NiAl3, Ni2Al3, and NiAl intermetallic phases. The NiAl3 phase content directly correlates with final catalyst surface area — XRD verification is standard at this stage. The ingot is crushed and sieved to 20-100 um particle size for electrode coating applications.

2. Caustic Leaching (Activation). The crushed Ni-Al powder is slowly added to 20-25% NaOH at 50-80 C with continuous stirring. The reaction 2Al + 2NaOH + 2H2O to 2NaAlO2 + 3H2 selectively dissolves aluminum while liberating hydrogen gas. Temperature control is the critical process variable: exceeding 100 C sinters the nickel skeleton and irreversibly reduces surface area. Leaching continues for 2-4 hours until hydrogen evolution ceases. The slurry is washed with deionized water to pH neutral to remove residual sodium aluminate.

3. Storage and Handling. Freshly leached Raney nickel, still wet from washing, contains adsorbed hydrogen at 50-100 m2/g BET surface area. If allowed to dry in air, it ignites spontaneously — pyrophoric. Commercial Raney nickel is supplied and stored under deionized water or isopropanol. For electrode manufacturing, the catalyst is kept wet until mixed into the catalyst ink slurry and immediately coated onto nickel mesh substrates. Once sintered, the catalyst is stabilized and non-pyrophoric.

Coating Raney Nickel onto Woven Nickel Mesh

The Raney nickel catalyst is only half the electrode. The other half is the conductive substrate that supports it — woven nickel mesh. The combination of Raney nickel catalyst on a nickel mesh current collector is the industry-standard electrode architecture for alkaline water electrolysis.

Mesh substrate specification: Woven nickel mesh, 30-40 mesh per inch, 0.25-0.30 mm wire diameter, plain weave, Ni201 grade — electropolished finish to eliminate edge burrs that cause coating defects and diaphragm puncture. This mesh count provides approximately 0.45-0.55 mm openings for catalyst slurry infiltration while retaining the coating.

Catalyst ink formulation: Raney nickel powder (20-50 um particle size, wet) mixed with PTFE dispersion at 5-15 wt% dry basis in a water/isopropanol solvent blend. The PTFE binder provides mechanical adhesion and creates hydrophobic gas-release channels. Typical catalyst loading: 10-30 mg/cm2 on the mesh substrate.

Coating and sintering protocol: The ink is applied via pneumatic spray coating to a uniform 50-200 um layer thickness. After drying at 80 C to remove solvents, the coated electrode is hot-pressed at 100-150 C under 5-10 MPa, then sintered at 300-350 C for 1-2 hours under N2 or Ar atmosphere. Sintering bonds the catalyst to the nickel mesh surface and decomposes the PTFE surfactant, producing a porous, mechanically stable electrode structure.

Bottom line: Raney nickel on woven Ni201 mesh (30-40 mesh, 0.25 mm wire, electropolished) is the proven electrode architecture for AWE stacks targeting 60,000+ hour lifetimes. The catalyst provides surface area; the mesh provides mechanical integrity and uniform current distribution. Specify both correctly.