Mechanistic Investigation of CO Hazard Elimination from Methane Explosion Using Co3O4 Catalyst

High-concentration carbon monoxide (CO) produced by incomplete methane combustion in underground explosions is the primary cause of post-explosion fatalities, with typical concentrations (2–4%) far exceeding human tolerance limits. Unsupported Co3O4 catalysts were synthesized via a hydrothermal route and evaluated for post-explosion CO elimination under realistic mine-atmosphere conditions. The phase-pure spinel catalyst (crystallite size ~18 nm, SBET = 68.5 m2/g) exhibited exceptional low-temperature activity with T50 = 43 °C and T90 = 59 °C under 10% O2, and an apparent activation energy of 63 kJ/mol, substantially outperforming commercial Hopcalite (T50 = 95 °C). In 20 L explosion vessel tests simulating 11% CH4 combustion at a catalyst loading of 200 g/m3, CO was reduced from 2.85% to 0.32% (89% reduction), extending the escape time factor to kes = 1.62. Continuous operation at 70 °C for 120 h maintained CO conversion above 96%, and three consecutive explosion cycles produced only a modest ~2% decline in activity, with post-test XRD confirming retention of the spinel phase. Mechanistic studies combining in situ DRIFTS and CO-TPD identify a Mars–van Krevelen pathway driven by surface Co3+ sites and reactive lattice oxygen.