Chong-Yong Lee

The tuning of the oxidation degree of PANI facilitates Cu²⁺ adsorption on quinoid –N sites, which promotes Cu (111) facet formation, leading to enhanced CH₄ selectivity in CO₂ electroreduction.

Cathodic exfoliation of graphite has emerged as an attractive method to synthesize high-quality and lo- defect graphene. Here, it is demonstrated that the type of starting graphite material influences the properties of exfoliated graphene. Graphite foil, natural graphite, and graphite rods were examined in the exfoliation processes performed in 3.0 M KCl at −15 V. The use of a graphite foil facilitates the rapid cathodic exfoliation process in comparison with structurally more compact natural graphite and graphite rods. For the graphite foil, the cathodically exfoliated graphene exhibits a low defect density (I_D/I_G of 0.09, a C/O ratio of 35) with graphite exfoliation yield of 92.8%. In contrast, the exfoliated graphene from natural graphite exhibits an I_D/I_G of 0.15, a C/O ratio of 28, and a graphite exfoliation yield of 30.5%, whereas graphene from graphite rod exhibits an I_D/I_G of 0.86, a C/O ratio of 30, and a graphite exfoliation yield of 19.5%. The dense structure of natural graphite and graphite rods led to longer exfoliation times. Exfoliation of graphite rods produced few-layer graphene with the smallest sheet size, whereas natural graphite and graphite foil yielded multilayer graphene with larger sheets. This study demonstrates the feasibility of using aqueous-based cathodic exfoliation to produce graphene from various graphite sources, leading to variations in sheet thickness, size, defect density, and solvent dispersibility.

Previous studies have shown that partially coating electrode surfaces with patterns of ‘islands’ of hydrophobic tetrafluoroethylene (PTFE; Teflon) may lead to more energy efficient gas generation. This occurred because the gas bubbles formed preferentially on the PTFE, thereby freeing up the catalytically active metallic surfaces to produce the gas more efficiently. This work examined electrochemically induced hydrogen bubble formation on a nickel electrode surface that had been coated with linear patterns of PTFE. The impact of the PTFE line size (width) and degree of coverage was examined and analyzed. No improvement in electrical energy efficiency was observed up to 15 mA/cm² when comparing the PTFE-coated electrodes with the control bare uncoated electrode. However, increasing PTFE coverage up to 15% generally improved electrolysis performance. Moreover, samples with 50% wider lines performed better (at the equivalent PTFE coverage), yielding an overpotential decline of up to 3.9% depending on the PTFE coverage. A ‘bubble-scavenging’ phenomenon was also observed, wherein bubbles present on the PTFE lines rapidly shrunk until they disappeared.

Polyaniline (PANI) provides an attractive organic platform for CO₂ electrochemical reduction due to the ability to adsorb CO₂ molecules and in providing means to interact with metal nanostructures. In this work, a novel PANI supported copper catalyst has been developed by coupling the interfacial polymerization of PANI and Cu. The hybrid catalyst demonstrates excellent activity towards production of hydrocarbon products including CH₄ and C₂H₄, compared with the use of bare Cu. A Faradaic efficiency of 71.8 % and a current density of 16.9 mA/cm² were achieved at −0.86 V vs. RHE, in contrast to only 22.2 % and 1.0 mA/cm² from the counterpart Cu catalysts. The remarkably enhanced catalytic performance of the hybrid PANI/Cu catalyst can be attributed to the synergistic interaction between the PANI underlayer and copper. The PANI favours the adsorption and binding of CO₂ molecules via its nitrogen sites to form *CO intermediates, while the Cu/PANI interfaces confine the diffusion or desorption of the *CO intermediates favouring their further hydrogenation or carbon‐carbon coupling to form hydrocarbon products. This work provides insights into the formation of hydrocarbon products on PANI‐modified Cu catalysts, which may guide the development of conducting polymer‐metal catalysts for CO₂ electroreduction.

Additive manufacturing (or 3D printing) has been increasingly employed for energy conversion and storage applications. Although it is still in the early stage of research and development, the utilization of 3D printing for electrochemical water splitting applications has gained significant interest. This eco-friendly manufacturing approach offers promising prospects in rapid prototyping and fabricating complex geometries that would assist in the innovations of water-splitting electrolyzers. In this chapter, we discuss the development of 3D printing technology for electrochemical water splitting applications. We discuss the principle and fundamentals of electrochemical water splitting, and the utilization of 3D printing techniques to fabricate both conductive and non-conductive components related to water splitting. Particularly, we emphasize the recent development of 3D-printed electrodes and the associated electrochemical cell designs that would impact the water splitting performance. Strategies such as catalyst assemblies during electrode fabrications, post-processing of printed electrodes, and advances in water splitting device fabrication are discussed. Finally, we discuss the benefits and limitations of 3D printing for electrochemical water splitting and offer our insights into future directions of this field.