Saiful Arifin Shafiee

Carbon materials, such as the boron-doped diamond (BDD), are commonly used in the field of electroanalytical sensors and chemical generators. This study focuses on using the scanning electrochemical microscopy (SECM) and the scanning electrochemical cell microscopy (SECCM) techniques for probing the surface heterogeneity of the carbon-based materials of interest. Three BDD electrodes with high concentrations of boron doping, were investigated in this study. The GC and HOPG electrodes were used as standards for their behaviour. The SECM results on the lowest doped BDD electrode (2.94×1020 cm−3; 2000 ppm) in this study imply that the BDD electrode behaves similar to a gold substrate: The feedback kinetic rate constant, kfeedback, obtained, was 0.009–0.013 cm s−1 (the gold substrate’s value: 0.014 cm s−1). The Raman spectra show that all the BDD electrodes exhibit metallic conductivity and also that the non-diamond carbon (NDC) cannot be removed from the BDD films. The presence of graphite, buckminsterfullerene, and fullerite were detected in the BDD films based on the X-Ray diffraction (XRD) spectra. A background current and a potential window study were performed, using the SECCM technique; the BDD electrode with the lowest boron doping shows the widest potential window among the electrodes of interest. This potential window decreases as the boron concentration increases. The results of the standard electrodes show that they share the same and narrowest potential windows among the carbon electrodes. The HOPG electrode has the smallest double layer capacitance while the GC electrode has a relatively large background current. As the boron concentration increases, the background currents for the BDD electrodes increase. The same carbon-based electrodes were also investigated in dissolved ferrocyanide using the SECCM technique. The results show that the GC electrode has the fastest kinetic transfer in comparison to the HOPG electrode. As the boron concentration increases, the kinetic transfer of the BDD electrodes increases.

The paramount importance of lithium (Li) nowadays and the mounting volume of untreated spent LIB have imposed pressure on innovators to tackle the near-term issue of Li resource depletion through recycling. The trajectory of research dedicated to recycling has skyrocketed in this decade, reflecting the global commitment to addressing the issues surrounding Li resources. Although metallurgical methods, such as pyro- and hydrometallurgy, are presently prevalent in Li recycling, they exhibit unsustainable operational characteristics including elevated temperatures, the utilization of substantial quantities of expensive chemicals, and the generation of emissions containing toxic gases such as Cl₂, SO₂, and NO_x. Therefore, the alternative electrochemical method has gained growing attention, as it involves a more straightforward operation leveraging ion-selective features and employing water as the main reagent, which is seen as more environmentally benign. Despite this, intensive efforts are still required to advance the electrochemical method toward commercialisation. This review highlights the key points in the electrochemical method that demand attention, including the feasibility of a large-scale setup, consideration of the substantial volume of electrolyte consumption, the design of membranes with the desired features, a suitable layout of the membrane, and the absence of techno-economic assessments for the electrochemical method. The perspectives presented herein provide a crucial understanding of the challenges of advancing the technological readiness level of the electrochemical method.

The increasing levels of carbon dioxide (CO₂) in the atmosphere may dissolve into the ocean and affect the marine ecosystem. It is crucial to determine the level of dissolved CO₂ in the ocean to enable suitable mitigation actions to be carried out. The conventional electrode materials are expensive and susceptible to chloride ion attack. Therefore, there is a need to find suitable alternative materials. This novel study investigates the electrochemical behaviour of dissolved CO₂ on roughened molybdenum (Mo) microdisk electrodes, which were mechanically polished using silicon carbide paper. Pits and dents can be seen on the electrode surface as observed using scanning electron microscopy. X-ray diffraction spectra confirm the absence of abrasive materials and the presence of defects on the electrode surface. The electrochemical surface for the roughened electrodes is higher than that for the smoothened electrodes. Our findings show that the roughened electrodes exhibit a significantly higher electrocatalytic activity than the smoothened electrodes for the reduction of dissolved CO₂. Our results reveal a linear relationship between the current and square root of scan rate. Furthermore, we demonstrate that saturating the electrolyte solution with CO₂ using a bubbling time of just 20 minutes at a flow rate of 5 L min⁻¹ for a 50 mL solution is sufficient. This study provides new insights into the electrochemical behaviour of dissolved CO₂ on roughened Mo microdisk electrodes and highlights their potential as a promising material for CO₂ reduction and other electrochemical applications. Ultimately, our work contributes to the ongoing efforts to mitigate the effects of climate change and move towards a sustainable future.