Plasmon-enabled N2 photofixation on partially reduced Ti3C2 MXene

Benefiting from the superior conductivity, rich surface chemistry and tunable bandgap, Ti3C2 MXene has become a frontier cocatalyst material for boosting the efficiency of semiconductor photocatalysts. It has been theoretically predicted to be an ideal material for N-2 fixation. However, the realization of N-2 photofixation with Ti3C2 as a host photocatalyst has so far remained experimentally challenging. Herein, we report on a sandwich-like plasmon- and an MXene-based photocatalyst made of Au nanospheres and layered Ti3C2, and demonstrate its efficient N-2 photofixation in pure water under ambient conditions. The abundant low-valence Ti (Ti(4-x)+) sites in partially reduced Ti3C2 (r-Ti3C2) produced by surface engineering through H-2 thermal reduction effectively capture and activate N-2, while Au nanospheres offer plasmonic hot electrons to reduce the activated N-2 into NH3. The Ti(4-x)+ active sites and plasmon-generated hot electrons work in tandem to endow r-Ti3C2/Au with remarkably enhanced N-2 photofixation activity. Importantly, r-Ti3C2/Au exhibits ultrahigh selectivity without the occurrence of competing H-2 evolution. This work opens up a promising route for the rational design of efficient MXene-based photocatalysts.