Dual low-temperature simultaneous catalytic combustion of methane and carbon monoxide in relevance to combating emission from natural gas vehicles (NGVs)

Due to incomplete combustion, natural gas vehicles (NGVs) release two major pollutants, methane (CH₄) and carbon monoxide (CO), which significantly contribute to global warming and pose a serious risk to human health. Addressing this dual emission problem requires an efficient and cost-effective catalysts that mitigate both pollutants at low temperatures. Herein, a series of bimetallic cobalt and nickel catalysts with varying Co:Ni ratios supported on cerium oxide (CeO₂) were synthesized by wet impregnation method to explore the effect of composition on simultaneous oxidation of CH₄ and CO. The prepared catalysts were thoroughly characterized using different techniques, in which the structural and surface analyses revealed the incorporation of both Co and Ni into the CeO₂ support in specific composition (1:1 Co:Ni ratio). Such incorporation induces lattice distortions and generates abundant oxygen vacancies, resulting in an exceptional catalytic activity achieving a 50 % of conversion (T₅₀) at low temperature of 239 °C and maintaining stability for over 12 h with a minimal variation in conversion. To simulate real combustion conditions, the influence of water vapor (1.5 vol%) and different weight hour space velocities (WHSVs) varying range of 15,000–29,400 cm³g⁻¹h⁻¹ on catalytic behaviour were examined, where higher WHSVs led to a decline in conversion of about 20 % compared with the optimum WHSVs. Overall, the synergistic Co:Ni doping in CeO₂ enhances oxygen vacancy formation and redox activity, offering a cost-effective alternative to noble-metal catalysts for the simultaneous abatement of CO and CH₄ in NGV exhausts.