A binary alloy powder for an electrode comprises either Co5-30% balance Pr or Nb5-30% balance Pr. In each case 20% is the preferred amount. 15% of each alloy is melted with 85% Si or Al and this is then burned out by acid or NaOH or KOH to form a powder that is bound by p.t.f.e. to form a cathode or a cathode layer.
