The biocarbon (SKPH) was obtained from Sargassum spp., and it was evaluated electrochemically as support for the CO2 reduction. The biocarbon was synthesized and activated with KOH, obtaining a high surface area (1600 m2 g− 1) due to the activation process. Graphitic carbon formation after pyrolysis was confirmed by Raman spectroscopy. The XRD results show that SKPH has an amorphous structure with peaks corresponding to typical amorphous carbonaceous materials. FTIR was used to determine the chemical structure of SKPH. The bands at 3426, 2981, 2851, and 1604 cm− 1 correspond to O–H, C-H, and C-O stretching vibrations, respectively. Then, it compares SKPH films with different carbon films using two electrolytic systems with and without charge transfer. The SKPH film showed a capacitive behavior in the KOH, H2SO4, and, KCl systems; in the acid medium, the presence of a redox couple associated with carbon functional groups was shown. Likewise, in the [Fe(CN)6]−3 and Cu(II) systems, the charge transfer process coupled with a capacitive behavior was described, and this effect is more noticeable in the [Fe(CN)6]−3 system. Electrodeposition of copper on SKPH film showed two stages Cu(NH 3)2+ 4 /Cu(NH 3)+ 2 and Cu(NH 3)+ 2 ∕Cu in ammonia media. Hydrogen formation and the activity of CO2 are observed on SKPH film and are favored by the carbon’s surface chemistry. Cu/SKPH electrocatalyst has a catalytic effect on electrochemical reduction of CO2 and inhibition of hydrogen formation. This study showed that the SKPH film electrode responds as a capacitive material that can be used as an electrode for energy storage or as metal support.

    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Preparation of biocarbon
        2.2 Carbon film electrodes preparation
        2.3 Physical–chemical characterization of samples carbon
    3 Electrochemical studies
    4 Results and discussion
        4.1 Physicochemical characterization of the SKPH biocarbon
        4.2 Fourier transform infrared spectroscopy (FTIR)
        4.3 XRD analysis
        4.4 Raman spectroscopy
        4.5 BET analysis
        4.6 SEM morphology characterization of carbon samples
        4.7 Physicochemical characterization electrocatalysts based on Cu supported on SKPH
        4.8 Electrochemical characterization of the carbon film samples
        4.9 Electrodeposition of copper on SKPH film
    5 Electrocatalytic behavior of the electrocatalysts in reducing CO2
    6 Conclusions
    Acknowledgements 
    References

• D. A. Pantoja Velueta(Facultad de Ingeniería, Universidad Autónoma del Carmen, Campus III, Av. Central S/N, Esq. con Fracc. Mundo Maya)
• S. J. Figueroa Ramírez(Facultad de Ingeniería, Universidad Autónoma del Carmen, Campus III, Av. Central S/N, Esq. con Fracc. Mundo Maya)
• J. M. Sierra(Facultad de Ingeniería, Universidad Autónoma del Carmen, Campus III, Av. Central S/N, Esq. con Fracc. Mundo Maya)
• B. Escobar(CONACYT‑Centro de Investigación Científica de Yucatán)
• C. A. Aguilar Ucán(Facultad de Química, Universidad Autónoma del Carmen)
• G. Rosas(Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo)