documentclass[varwidth,border=10pt]{standalone}
usepackage{expl3}
usepackage{newunicodechar}
ExplSyntaxOn

cs_new_protected:Nn someToken:n {
    peek_catcode:NF ## {
        char: #1\
        -~Meaning~of~next~token:~token_to_meaning:N l_peek_token\
        -~Prefix~of~next~token:~token_get_prefix_spec:N l_peek_token\
        -~Name~of~next~token:~token_to_str:N l_peek_token\ % this is not working as wanted, I want someToken:n !
    }
}

newunicodechar{➀}{someToken:n{a}}
newunicodechar{➁}{someToken:n{b}}
ExplSyntaxOff
begin{document}
➁➀
…
end{document}