## 4 Conclusions  
Coal-derived CDPC has been successfully fabricated via the modified Hummers method, using Vietnamese coal as the precursor. The fabricated nanomaterials have an average size of 3-10 nm and a porous nature. The existence of macropores and mesopores will not only assist electrolytes in penetrating the materials in full depth but also shorten the ion diffusion paths effectively. When being used as the anode electrode in a supercapacitor, the CDPC electrode exhibited excellent performance. Via EIS, Nyquist plots demonstrated the superior conductivity of the CDPC electrode, characterized by minimal charge-transfer resistance. This electrode showcased remarkable stability, retaining 74.7% of its capacitance after 1000 cycles. The constant current discharge method was used to determine that the specific capacitance of CDPC was 236 F/g at a current density of 0.1 A, exhibiting the expected reduction with increasing current density. The overall electrochemical evaluation underscores the commendable and stable energy storage capacity of the CDPC material. Overall, these findings collectively emphasize the potential of CDPC as a promising candidate for energy storage applications. This study demonstrates the potential of using Vietnamese coal to produce high-performance nanomaterials for energy storage applications. Further exploration and optimization of CDPC-based devices could promote advancements in energy storage technologies, as well as the development of new energy storage devices to meet the growing energy demand. Writing--original draft preparation, T.H.D. and V.T.N. ; conceptualization, X.L.H. ; software, V.T.N. and X.L.H. ; data curation, T.N.N. and Q.D.N. ; methodology, T.N.N.N. and T.K.N.T. ; formal analysis, Q.D.N. ; writing--review and editing, T.K.N.T. and T.H.D. ; supervision, T.H.D. All authors have read and agreed to the published version of the manuscript. This study was funded by the ministerial-level Science and Technology project, at the Ministry of Education and Training of Vietnam, budget 730,000,000 VND, code B2023-TNA-07. Not applicable. This study was funded by the ministerial-level Science and Technology project, at the Ministry of Education and Training of Vietnam, budget 730,000,000 VND, code B2023-TNA-07. * _[PERSON] et al. (2018)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Preparation and characterization of coal-based carbon foams by microwave heating process under ambient pressure. _Diam. Relat. Mater._**2018**, _86_, 63-70. [CrossRef]
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