B powder

The non-carbon precursors for carbide synthesis are Ti powder (Johnson Matthey, 99%), Zr(OH)₄ powder (Sigma-Aldrich, 97%), HfO₂ powder (Alfa Aesar, 99.95%), VO₂ powder (Alfa Aesar, 99%), NbCl₅ powder (Sigma-Aldrich, 99%), TaCl₅ powder (Sigma-Aldrich, 99.8%), Cr powder (Alfa Aesar, APS < 10 μm, 99.2%), MoCl₃ powder (Fisher Scientific, 99.5%), WO₃ powder (Johnson Matthey, 99.998%), B powder (Alfa Aesar, 99.9%), and SiO₂ powder (Sigma-Aldrich). Carbon black (Cabot, VULCANXC72R) is used at the carbon source as well as the conductive additive.

Mo powder (Metco), B powder (Sigma-Aldrich, > 95%, < 1 µm), Al powder (Australian Metal Powders Supplies, > 99%, 45 µm), Nafion^® perfluorinated resin solution (Sigma-Aldrich, 5 wt%), Nafion^® 117 membrane, potassium hydroxide (Sigma-Aldrich, 90%), low-level ammonia pH adjusting ISA (Thermo SCIENTIFIC), ammonia standard solution (Thermo SCIENTIFIC), phenol (BDH Laboratory Supplies), ammonium sulfate (BDH Chemical, Australia Pty. Ltd.), ethanol (Merck KGaA), sodium nitroferricyanide (III) dehydrate (Sigma-Aldrich, > 99%), trisodium citrate dehydrate (Sigma-Aldrich), sodium hydroxide (Sigma-Aldrich), sodium hypochlorite solution (Sigma-Aldrich) and deionized water (Millipore, 18.2 MΩ cm) was used as the solvent, N₂ gas (99.99%) and Ar gas (99.99%). All chemical regents were used as received without further purification.