Evidence of ambient pressure methanol production on Ni-Ga-Ca dual function materials and dynamic restructuring effects on selectivity

This study reports a dual function material (DFM) composed entirely of non-precious metals for methanol production (13.8 μmol/g material) at ambient pressure from passively captured CO$_2$ from the air. While state of the art carbon capture and utilisation (CCU) processes rely on expensive CO$_2$ capture systems and a high-pressure catalytic reactor for methanol synthesis, this Ni-Ga-Ca DFM can be an enabler for significant energy efficiency gains in methanol synthesis from CO$_2$ through the direct utilisation of dilute emissions and substantially lower operating pressures. Using operando DRIFT spectroscopy coupled with density functional theory, XAFS, XRD, and TEM-HAADF, a combination of Ni-Ga intermetallic species and their oxides are identified as the active sites. During cyclic operation a shift in selectivity towards methane is observed, which is associated with dynamic restructuring of the DFM. Guided by mechanistic and structural understanding, a synthesis strategy is developed to enhance cyclic stability by mitigating dealloying and Ni particle agglomeration. It is indicated that cyclic stability can be achieved by strengthening the Ni-Ga-Ca interaction, however, there remains a gradual shift in selectivity towards methane which highlights the need for further material optimisation.