Two-dimensional MBenes for next-generation energy storage and electrocatalysis

Boron derivative of MXene, MBenes exhibit compelling characteristics. The ongoing review provides comprehensive overview of the advancement in synthesis procedures, characteristics and in-depth discussion of applications of MBenes. MBenes present exposed boron sites, and tunable interlayer spacing which facilitates strong yet reversible ion adsorption for high performance metal- ion batteries. MBenes, particularly when functionalized with oxygen or doped with dual metals, show promising bifunctional activity (oxygen evolution or reduction) with low overpotentials <0.5 V (as low as 0.26 V in Ni2B2), crucial for fuel cells and metal- ion batteries. MBenes combine ultra- high theroretical capacities (even >1000 mAhg-1 for various MB3 type MBenes), exceptional cycling stability (88- 89% retention over 1000- 3000 cycles in HfBO and superior structural durability compared to many conventional 2D anodes and MXenes. MBenes offer fluorine- free synthesis routes (NaOH hydrothermal at 150 °C yielding 73.2% pure MoB) as safer, scalable alternatives to HF etching, thus reducing environmental risks. Thereupon MBenes demonstrate exceptional potential across the renewable energy domain, from storing ions in batteries to catalysing the conversion of small molecules into valuable fuels and chemicals. Additional probable features are yet to be explored. Hence MBenes hold a propitious future in energy conversion, storage and harvesting.