Effective utilization of waste: Development of CH₄ dry reforming catalysts from spent nickel metal hydride battery for resource recovery

The resource recovery of nickel metal from the spent nickel metal hydride (Ni-MH) battery was investigated by using the CH₄ dry reforming, aiming at reusing it as a raw material of the Ni-MH battery. From the results, a compound identified as a single phase of NiO by XRD was successfully prepared from the spent Ni-MH battery by a series of chemical processes using HCl and NH₃ aq. solutions followed by calcinations. The resulting NiO exhibited excellent CH₄ conversion in the CH₄ dry reforming, i.e., the CH₄ conversion higher than 96% continued for 50 h when the flow rates of injection gases were controlled at CH ₄/CO₂/Ar = 10:10:80 ml·min^-1. Although the XRD pattern revealed the reduction of NiO to Ni⁰ and the deposition of carbon after the CH₄ dry reforming, the deposition of carbon could be suppressed by changing the injection gas ratio. The resource recovery of nickel metal was, therefore, concluded to be possible through the CH₄ dry reforming over NiO prepared from the spent Ni-MH battery.