Is HCO3 both a bronsted acid and base?

HCO3- is both an acid and a base. It can donate a "proton" (hydrogen ion) as follows:

HCO3(-) = H(+) + CO3(-2)

or

HCO3(-) + OH(-) = H2O + CO3(-2)

It can also absorb a proton:

HCO3(-) + H(+) = H2CO3

Which occurs depends on the pH of the solution. The pKa values are given here:

What_is_pka_value_for_sodium_bicarbonate

H2CO3 is known as "carbonic acid". It can decompose into water and carbon dioxide

H2CO3 = H2O + CO2