Fig. 2

CO2-dependent thermal expansion trends for Co-NP and FeCo-PB. a, b Symbols represent the experimentally determined cubic lattice parameters of Co-NP and FeCo-PB at various CO2 loadings and temperatures. Error bars are smaller than the symbols. Solid lines represent linear regression fits over limited data ranges (see Table 1); these fits were used to parameterise the formulae derived in the text (see Eqs. (1) and (2)). The dashed trend lines are predicted by the parameterised model. c Evolution of the CTE values obtained by linear regression fits against all data series