Navigating Cation Ion Effect for Artificial Photosynthesis of Methanol in Natural Seawater

The artificial photosynthesis of alcoholic products in natural seawater faces significant challenges, mainly including ion-interference and catalyst-corrosion, which generally results in reduced catalytic performance in natural seawater for majority of photocatalysts when compared with pure water. Here, we study the artificial photosynthesis of methanol in natural seawater based on a heterojunction photocatalyst (i.e. Cu2O/BMO, BMO = Bi2MoO6) and report a cation-mediated protective mechanism. Notably, it achieves an unprecedented CH3OH generation rate (501.62 μmol g-1 h-1) with high selectivity (95.8%) and long-term stability (>3 days) in natural seawater, affording abnormal performance enhancement when compared with that in pure water and surpassing the majority of reported photocatalysts to date. Theoretical calculations demonstrate that the enhanced performance in natural seawater compared to pure water arises from the strong interaction between Cu2O/BMO and cation ions that uniquely transforms the conventional ionic interference effect into a cation-mediated protective mechanism. Notably, on Cu2O/BMO surface, the cation ions (e.g., Ca2+ and Mg2+) could shield the active sites by mitigating hydroxyl (OH-) interference and stabilize the key reaction intermediates, thus enhancing both activity and stability of the overall artificial photosynthesis system.