New hydrogen adsorption states on Li, Na, and Mg-decorated graphene-type BC3 sheet have been investigated by first-principles calculations. The structural, electronic and binding properties, metal binding and nH(2) (n = 1-10) adsorption states of these systems are studied in detail with the Mulliken analysis, charge density differences, and partial density of states. To enhance the number of the adsorbed H-2 molecules per metal atom, and also to generate the better initial coordinates for reducing the simulation time, we present two masthematical algorithms (CLICH and RICH). The tested results on BC3 sheet and boron-doped graphene (C30B2) show that these algorithms can increase the number of adsorbed hydrogen molecules by minimizing the computational time. It is seen that nH(2) (n = 1-10) adsorbed Li,/Na and/Mg-decorated BC3 single- and double-sided systems are industrial materials for hydrogen storage technology, their adsorption energies fall into the acceptable adsorption energy range (0.20-0.60 eV/H-2). It is concluded from the optimized geometries and charge density differences for the higher number of H-2 adsorbed systems that not only decorated metal atom but also the sheet plays an important role in hydrogen storage process, because the boron atoms in the sheet expand the induced electric field between the adatoms and BC3 sheet. From Mulliken analysis, there is a charge transfer mechanism between H-2 molecules and metal atoms. Moreover, the resonant peaks for the sheet, metal atoms and H-2 molecules in partial density of states curves indicate the possible hybridizations. Additionally, these adsorption processes are supported by charge density difference plots. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.