Efficient diode-pumped passively Q-switched Er:Lu2O3 laser operation at 2.84 μm was realized. A few-layer MoS2nanosheet film on a YAG substrate, was fabricated and employedas saturable absorber (SA) in a short plane-planecavity. Under an absorbed diode laser pump power of7.61 W, an average output power of 1.03 W was generatedwith a pulse duration of 335 ns and a repetition rate of121 kHz, resulting in a pulse energy of 8.5 μJ.