Catalytic gasification of phenol in supercritical water over bimetallic Co–Ni/AC catalyst

Solid-solution bimetallic alloy catalysts containing no noble metals were developed via both simultaneous and sequential deposition in supercritical water (SCW). These bimetallic nano-catalysts were analyzed by Brunauer–Emmett–Teller, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Obvious downward shifts are observed in diffraction peaks, situated between the peak (1 1 1) for Co and the peak (1 1 1) for Ni. The shifts indicate the formation of NiCo solid-solution bimetallic alloy(s). The bimetallic nanoparticles show high activity for supercritical water gasification of phenol to produce gaseous fuels. The carbon gasification efficiency (CGE) of phenol in SCW can reach 95% on the Co–Ni/AC catalyst at conditions of 500°C and 30 min, showing nearly the same CGE as the commercial noble-metal-based catalyst, such as Ru/C (5 wt% Ru) from Sigma-Aldrich. The Co–Ni/AC catalyst also shows high stability. Therefore, deposition in SCW provides an effective way to create noble-metal-free solid-solution bimetallic alloy catalysts.