Constructing MoO3@MoO2 heterojunction on g-C3N4 nanosheets with advanced Li-ion storage ability

Highlights: • MoO₃@MoO₂ heterojunction are anchored on two dimensional g-C₃N₄. • g-C₃N₄ provides abundant active sites and relieves large volume expansion effect. • MoO₃@MoO₂ heterojunction could accelerate the Li⁺/e^– transfer. • MoOx-UCN electrode shows excellent lithium-ion storage and rate performance. -- Abstract: Because of multi-valence state of molybdenum (Mo), MoO₃@MoO₂ heterojunction anchored on two dimensional (2D) g-C₃N₄ nanosheets is created by calcining ammonium heptamolybdate with urea in a muffle furnace. The 2D porous structure of g-C₃N₄ provides abundant active sites for lithium-ion storage, and it helps enhance the electrical conductivity and relieve large volume expansion effect during the discharge/charge process. The MoO₃@MoO₂ heterojunction can accelerate the Li⁺/e^- transfer, further improving sluggish charge transport kinetics and supplying high pseudocapacitive. Therefore, the resulting MoO₃@MoO₂ heterojunction on g-C₃N₄ electrode delivers a high capacity of 992 mAh g⁻¹ 0.5 Ag⁻¹ after 100 cycles and excellent rate performance. It still shows stable cycling performance when assembled into a full lithium-ion battery.