LAUSR

Ultrathin nanosheets of non‐layered materials have attracted intensive interests due to their abundantly accessible active sites. Herein, we demonstrate that the ultrathin FeP nanosheets (FeP‐I NS) with abundant mesoporosity and phosphate dopants can be facilely synthesized using ultrathin γ‐Fe2O3 NS as precursors. The as‐prepared catalyst displays good HER catalytic activity with an low overpotential (η) of 95/160 mV at the current densities of 10/100 mA cm−2 and small Tafel slope of 41 mV dec−1 as well as good stability during a period of 24 h in acid media. Additional experimental results reveal that the unique structural features of FeP‐I NS (i. e., ultrathin morphology, abundant mesoporosity, local structural distortion and amorphous domains) are key factors for achieving good HER activity. The computational studies demonstrate that the phosphate dopants (i. e., Fe2P2O7) contribute to the superior catalytic performance of FeP by reducing the Gibbs free energy of intermediate H* adsorption (ΔGH*) to the catalyst surface as well as by tailoring the electronic properties of the catalyst.