High‐Yield Production of Monolayer FePS 3 Quantum Sheets via Chemical Exfoliation for Efficient Photocatalytic Hydrogen Evolution

2D layered transition metal phosphorus trichalcogenides (MPX 3 ) possess higher in‐plane stiffness and lower cleavage energies than graphite. This allows them to be exfoliated down to the atomic thickness. However, a rational exfoliation route has to be sought to achieve surface‐active and uniform individual layers. Herein, monolayered FePS 3 quantum sheets (QSs) are systematically obtained, whose diameters range from 4–8 nm, through exfoliation of the bulk in hydrazine solution. These QSs exhibit a widened bandgap of 2.18 eV as compared to the bulk (1.60 eV) FePS 3 . Benefitting from the monolayer feature, FePS 3 QSs demonstrate a substantially accelerated photocatalytic H 2 generation rate, which is up to three times higher than the bulk counterpart. This study presents a facile way, for the first time, of producing uniform monolayer FePS 3 QSs and opens up new avenues for designing other low‐dimensional materials based on MPX 3 .