Cobalt-,　iron-,　and　copper-substituted　nickel-aluminum　hydrotalcite-like　compounds　(Ni-2.7Co0.3Al,　Ni2.7Fe0.3Al,　Ni2.7Cu0.3Al　HTlcs)　have　been　synthesized　and　used　as　precursors　to　prepare　Ni-Co,　Ni-Fe,　and　Ni-Cu　alloy　catalysts　for　methane　decomposition.　The　catalysts　before　and　after　reaction　were　characterized　with　various　techniques　including　XRD,　H-2-TPR,　HAADF-STEM-EDX,　SEM,　TEM,　and　Raman.　The　characterization　results　indicate　that　upon　calcination　HTlcs　are　transformed　into　a　mixed　oxide　solid　solution,　where　cobalt,　copper,　and　iron　ions　are　incorporated　into　the　nickel　oxide,　and　the　reduction　treatment　leads　to　composition-uniform　alloy　particles.　In　methane　decomposition　at　600　degrees　C,　alloying　Ni　with　Co,　Fe,　and　especially　Cu　is　found　to　enhance　the　catalytic　life　and　carbon　yield.　The　order　of　activity　is　Ni2.7Cu0.3Al　＞＞　Ni2.7Fe0.3Al　＞　Ni2.7Co0.3Al　＞　Ni3Al　in　terms　of　carbon　yield,　highlighting　that　Ni-Cu　alloying　is　the　most　effective.　Besides,　Ni-Cu　alloying　remarkably　changes　the　carbon　morphology,　giving　carbon　nanofibers　as　the　main　product.　TEM　and　STEM　measurements　suggest　that　Ni-Cu　alloy　particles　are　readily　aggregated　into　big　particles　(＞60　nm)　under　the　reaction　conditions,　which　may　be　responsible　for　the　significant　effect　of　Ni-Cu　alloying.　(C)　2020　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.