Two-dimensional carbon nanosheets codoped with N and P species have been successfully synthesized by a template carbonization method coupled with nitrogenization and phosphorylation processes using trisodium citrate dehydrate, melamine, and NH4H2PO4 as C, N, and P sources, respectively. Dopants of N and P species play crucial roles in the determination of carbon porosities and electrochemical performance; notably, increasing the P content can lead to a decrease in the BET surface area together with a corresponding decrease in the electrochemical performance. For instance, regulating the mass ratio between the C source and the N and P sources to 2:1 results in the maximum BET surface area of 1340 m(2) g(-1), whereas a ratio of 1:2 results in a decreased value of only 47 m(2) g(-1). Moreover, the mass ratio of 1:1 results in superior electrochemical behaviors, with a maximum energy density that can reach up to 13.3 Wh kg(-1). The present synthesis method provides an alternative route for producing N- and P-containing carbon nanostructures with two-dimensional features, serving as excellent electrode materials for energy propagation and storage.