Optimizing the Ni/Cu Ratio in Ni–Cu Nanoparticle Catalysts for Methane Dry Reforming

Methane dry reforming (MDR) converts greenhouse gases into syngas. Exploring active catalysts to achieve stable MDR performance is still a great challenge because of the sintering and carbon deposition that occur at high temperatures. In this study, we rationally synthesized Ni–Cu alloy nanoparticles (approximately 5 nm) and utilized electrostatic adsorption for the MDR reaction. The miniscule alloy catalysts had low carbon deposition and trace sintering features, which contributed to a more active and stable MDR reaction than achievable with a pure Ni catalyst. The performance depended on the Cu/Ni ratio, and the highest performance was obtained at a Cu/Ni weight ratio of 0.5:4, followed by ratios of 0.2:4 and 1.5:4. This is because adding a proper quantity of Cu promoted the activation of CO2, which enhanced the transformation of CHx into syngas on Ni atoms, while excessive Cu addition formed individual Cu nanoparticles, which influenced Ni atoms on the surface and made the activation of CH4 harder. This work not only fabricated miniscule alloy nanoparticles but also demonstrated the importance of the Ni/Cu ratio for enhancing the MDR performance.