Figure The evolution of the free energy path with the lowering of temperature shifts the TDI and the TDTS of the energetic span model, and the inflection point is at 498 K of Li4RuH6 catalyst surface. For the lower temperature range (< 498 K), the TDI and TDTS are the initial/final state (state-0) and the transition state of the third hydrogenation (TS3-4) on the surface, respectively. In the higher temperature range (≥ 498 K), the TDI and the TDTS are the second H2(g) adsorption (state-12) and the transition state of the first H2 (g) adsorption (TS4-5) on the surface respectively. With further increase in temperature, state-9 comes energetically closer to state-12. At 573 K, the TDI and the TDTS are state-9 and TS4-5, respectively. The inserted plot shows the schematic presentation of the shift in TDI/TDTS. The TDI and TDTS at different temperature ranges are marked by the square-and circle-symbols, respectively, in the free energy plot and the inserted plot. We applied a fixed total pressure of 1 bar (N2:H2=1:3) to generate the free energy paths and barriers using density functional theory based free energy estimations and nudged elastic band method.