Lanthanum-mediated enhancement of nickel nanoparticles for efficient CO2 methanation

The investigation into CO2 conversion technologies has gained momentum due to escalating concerns about climate change and the pressing need for sustainable energy sources. While Ni-based catalysts have shown promise in CO2 methanation, they often exhibit moderate activity. In this study, we sought to address this limitation by incorporating La into Ni nanoparticles supported on SiO2 using the ammonia evaporation method. The La-doped Ni/SiO2 catalyst demonstrated a significant improvement in CO2 conversion, achieving a competitive 71.1 % compared to the 40.2 % observed with the Ni/SiO2 catalyst at 275 °C. This improvement is evident in the high space–time yield of methane (STYCH4) at 227.3 mmol/(g·h) and a turnover frequency of (TOFCO2) at 0.36 s−1. The incorporation of La species modifies the electronic properties of Ni through electron transfer from Ni to La, resulting in a Ni-La interaction effect. Temperature-programmed reduction and desorption, probed by H2 and CO2, reveal enhanced hydrogen atom spillover and stronger CO2 adsorption capacity on the La-doped Ni-based catalyst. Density functional theory (DFT) calculations unraveled the underlying mechanisms of La-mediated enhancement, elucidating lower adsorption for CO2 energy barrier and facilitated activation of CO bonds on the La-doped Ni-based catalyst. In-situ DRIFTS results indicated that, despite both catalysts following a CO pathway, La-doped Ni/SiO2 possessed more accessible active sites for CO2 methanation, whereas Ni/SiO2 shows higher occupancy of active sites by adsorbed CO and formate species.