Thermochemical two-step CO2 splitting is a potential approach that fixes the sustainable resource into transportable liquid fuels.However,the harsh CO2 splitting conditions,the limited oxygen release kinet-ics and capacity of metal oxides block further promoted the CO yield and solar-to-fuel energy efficiency.Here,we propose a different carbon cycle assisted by Ni/La2O3 via coupling methane decomposition with thermochemical CO2 splitting,replacing conventional metal oxides cycle.Superior performance was demonstrated with methane conversion reached around 94％ with almost pure H2 generation.Encouragingly,CO2 conversion of 98％ and CO yield of 6.9 mmol g-1 derived from CO2 were achieved,with peak CO evolution rate (402 mL min-1 g-1) of orders of magnitude higher than that in metal oxide pro-cess and outstanding thermodynamic solar-to-fuel energy efficiency (55.5％ vs.18.5％).This was relevant to the synergistic activation of La2O3 and Ni for CO2 in carbon cycle,thus improving CO2 splitting reaction with carbon species.