An electrocatalyst for the hydrogen evolution reaction has been successfully synthesized from graphene oxide (GO) decorated with the mesoporous NiFe₂O₄. A high catalytic activity performance was reached by using the GCE surface as a conductor, and the synthesized composite contained GO/NiFe₂O₄. Based on the results, the as-prepared electrocatalyst exhibited a high overpotential for the HER reaction of 36 mV vs. RHE at a 10 mA current density, with an electrochemical active surface area (ECSA) of 3.18 × 10⁻⁴ cm². Additionally, the electrocatalyst demonstrated a considerably good performance after the 9000 s stability test. It is believed that such an enhancement in electrocatalytic activity was due to the synergistic effect between the unique porosity feature of the mesoporous NiFe₂O_4, which may provide a more active surface, and the high conductivity of the GO.

Boron-doped diamond (BDD) was modified with copper and gold particles by using an electrodeposition technique to improve its catalytic effect on CO ₂ reduction in a flow system.

The synthesis of mesoporous carbon was successfully performed through solid–solid phase reaction employing banana peel powder as the carbon source and silica gel 60 (SG-60) as the hard template. The synthesis was initiated by hydrothermal heating to introduce the banana powder to SG-60 surface, followed by the carbonization process to form the mesoporous carbon. FTIR, Raman, XRF, and XRD characterization confirmed the success of the carbonization step, while N₂ physisorption and TEM characterization confirmed the mesoporous structure formation of the synthesized carbon with the template. At an optimum carbon-to-silica precursor ratio of 3 : 1, the synthesized carbon with SG-60 templates proceeds to a specific surface area of 476.97 m₂ g⁻¹, which is around 55-fold higher than the one synthesized without any template. Furthermore, evaluation of the capacitance performances was done by creating composite electrodes with nickel foam as the support and polyvinylidene difluoride as the binder. The evaluation was carried out using cyclic voltammetry in 3.0 M KOH, galvanic charge–discharge, and electrochemical impedance spectroscopy confirming a high correlation between the specific surface area and the specific capacitance. The banana peels-derived mesoporous carbon demonstrates a specific capacitance value of 23.1 F g⁻¹, measured using the cyclic voltammetry method. Good stability of the prepared electrode over 2500 voltammetric cycles was also demonstrated, indicating that the use of SG-60 as the hard template is suitable for synthesizing carbon with mesoporous structure from biomass.

Biomass-derived carbon, obtained from renewable organic materials, offers several advantages, including sustainability, cost-effectiveness, and excellent electrochemical properties, such as high energy and power densities, adjustable morphologies, and cycling stability. However, the limitation of carbon-based materials can be addressed through surface modification with layered materials such as, layered double hydroxides, metal dichalcogenides, graphene, vanadium pentoxide and the new emerging material MXene. This review highlights techniques particularly heteroatom doping and chemical or physical activation to further enhance the electrochemical performance of biomass-derived carbon as supercapacitors. It also examines the synthesis of MXenes, two-dimensional transition metal carbides and nitrides, known for high conductivity, structural stability, and versatile surface chemistry. Despite these advantages, MXenes face challenges such as self-oxidation, self-discharging, and nanosheets restacking, which limit long-term stability. The effective strategies including surface and interlayer modifications and optimized synthesis route, are explored to significantly improve the electrochemical performance MXene-based composites. Additionally, the enrichment of biomass waste and the role of MXenes in electrical double-layer (EDLCs) and pseudocapacitance are emphasized, with MXene offering continuous electron transport channels, high oxidation resistance, and structural stability. Ultimately, integrating biomass-derived carbon with MXenes offers promising pathway to develop high-performance, sustainable supercapacitors for efficient energy storage solutions in future applications.