The process for obtaining M.sup.1-BH.sub.4, the process comprising contacting M.sup.1-BO.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

The process for obtaining M.sup.1-BH.sub.4, the process comprising contacting M.sup.1-BO.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

Disclosed is a method for producing a metal borohydride and/or H.sub.2, including: A. producing a metal borohydride in a synthesis process, in which H.sub.2 is a reactant and the reaction further takes metal hydroxide and boron oxide or further takes metal boron oxide; B. producing H.sub.2 in a chemical reaction process, in which metal borohydride produced in step A and H.sub.2O are reactants, the amount of H.sub.2 produced in step B being larger than the amount of H.sub.2 required as a reactant in step A for the same amounts of metal borohydride as a reactant and a reaction product in steps B and A, respectively; and C. providing H.sub.2 produced in step C to step A, and repeating steps A, B and C. Part of the metal borohydride and/or H.sub.2 is withdrawn while leaving an amount of metal borohydride and H.sub.2, respectively, so as to allow repeating steps A-C.

Disclosed is a method for producing a metal borohydride and/or H.sub.2, including: A. producing a metal borohydride in a synthesis process, in which H.sub.2 is a reactant and the reaction further takes metal hydroxide and boron oxide or further takes metal boron oxide; B. producing H.sub.2 in a chemical reaction process, in which metal borohydride produced in step A and H.sub.2O are reactants, the amount of H.sub.2 produced in step B being larger than the amount of H.sub.2 required as a reactant in step A for the same amounts of metal borohydride as a reactant and a reaction product in steps B and A, respectively; and C. providing H.sub.2 produced in step C to step A, and repeating steps A, B and C. Part of the metal borohydride and/or H.sub.2 is withdrawn while leaving an amount of metal borohydride and H.sub.2, respectively, so as to allow repeating steps A-C.

Provided are methods of producing cobalt-based nanoparticles (Co.sub.xB.sub.y NPs) of a pre-selected diameter. The methods include reducing Co.sup.2+ ions with a sodium borohydride (NaBH.sub.4) solution having a selected ratio of tetrahydroxyborate (B(OH).sub.4.sup.) to tetrahydroborate (BH.sub.4.sup.) based on the pre-selected diameter, where the ratio of B(OH).sub.4.sup. to BH.sub.4.sup. is positively correlated with the pre-selected diameter. Also provided are methods of using the Co.sub.xB.sub.y NPs to produce hollow metal nanospheres (HMNs). Methods of producing Co.sub.xB.sub.y NP core/metal shell structures are also provided, such methods including combining in an anaerobic galvanic exchange reaction a deaerated solution including Co.sub.xB.sub.y NP scaffolds and a deaerated solution including a metal. Also provided are methods of producing HMNs from the Co.sub.xB.sub.y NP core/metal shell structures. Compositions and kits that find use in practicing the methods of the present disclosure and using HMNs produced in accordance with the methods of the present disclosure, are also provided.

The process for obtaining M.sup.1BH.sub.4, the process comprising contacting M.sup.1-B0.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

The process for obtaining M.sup.1BH.sub.4, the process comprising contacting M.sup.1-B0.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

The process for obtaining M.sup.1-BH.sub.4, the process comprising contacting M.sup.1-BO.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

The process for obtaining M.sup.1-BH.sub.4, the process comprising contacting M.sup.1-BO.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.

The process for obtaining M.sup.1BH.sub.4, the process comprising contacting M.sup.1-B0.sub.2 with a metal M.sup.2 in the presence of molecular hydrogen (H.sub.2) under conditions permitting the formation of M.sup.1-BH.sub.4 and M.sup.2-oxide, wherein the M.sup.1 is a metal selected from column I of the periodic table of elements or alloys of metals selected from column I of the periodic table of elements and M.sup.2 is a metal or an alloy of metals selected from column II of the periodic table of elements, provided that M.sup.2 is not Mg and M.sup.1 is different from M.sup.2.