Carbon foams, doped carbon composites, processes for fabricating carbon foams and doped carbon composites, and uses thereof

A process for forming a composite, the process comprising:

• loading a feedstock into a reactor, the feedstock comprising lignocellulosic biomass and a sulfur source, a silicon source, or a combination thereof different from the lignocellulosic biomass;
• and
• pyrolyzing the feedstock to form the composite, comprising:
• pressurizing the reactor with CO2, N2, H2O, or combinations thereof, the CO2, N2, H2O, or combinations thereof in a supercritical state or subcritical state, the pressure of the reactor is from about 1 MPa to about 20 MPa;
• contacting the feedstock with the CO2, N2, H2O, or combinations thereof;
• and
• heating the reactor at a heat rate of about 10° C./min to about 50° C./min until the reactor reaches a specified temperature of about 200° C. to about 800° C. to form the composite.