Turquoise hydrogen is produced through a process of separating carbon into solid carbon based on fossil fuels and refers to hydrogen that does not produce carbon dioxide. In this study, the characteristics of turquoise hydrogen production through a methane thermal cracking reaction using an arc plasma torch were investigated. The plasma torch operated stably under high voltage and transport gas flow conditions. The composition of the gas generated from the methane plasma reaction was analyzed using an online IR gas analyzer and GC-FID. The experimental results show that the hydrogen yield decreased to 16.4% as the methane feed rate increased but increased to 58.8% as the plasma power increased. Under these conditions, the yield of solid carbon, a valuable byproduct, was also shown to increase to 62.9%. In addition, solid carbon showed high-temperature heat-treated characteristics based on its generation location. Carbon oxides such as CO and CO₂ are rarely generated under any experimental conditions. Consequently, it can be considered that plasma thermal cracking is a promising technology for CO₂-free hydrogen production and a valuable solid carbon.

Solid fuelization technology can increase the heating value of sewage sludge such that it can be utilised as a fossil fuel substitutes. Reducing landfilling of bottom and fly ash resulting from heavy metals contained in sewage sludge is challenging. Hence, combustion melting technology (CMT), which can discharge bottom ash in the form of slag, has been proposed herein as an alternative to the conventional incineration technology. However, further research is required to improve the flowability of slag. Applicability of CMT for the stable treatment of heavy metals in the ash generated during the energisation of sewage sludge solid fuel has been reviewed. The change in the degree of fluidity was identified via a laboratory-scale fluidity measurement experiment following changes in melting temperature, mixing ratio of sewage sludge and sawdust, and basicity. The pouring index (PI) of sewage sludge solid fuel (pellet) was maintained at a level of about 60% at a basicity index of 0.8. Based on the results, the slagging rates and volume reduction rates, exhaust gas analysis, and heavy metal elution characteristics under oxygen enrichment were derived from a 2 ton/day combustion melting pilot plant experiment; thereafter, the feasibility of combustion melting of sewage sludge solid fuel was determined.

Turquoise hydrogen refers to hydrogen produced through a fossil-fuel-based process in which carbon is separated into solid carbon and no carbon dioxide is produced. In this study, dodecane was selected as a simulated oil for waste plastic pyrolysis recovery oil, and the turquoise hydrogen production characteristics through the thermal cracking reaction using an arc plasma torch were investigated. The plasma was stably discharged at 2 to 4 kW. Hydrogen in the produced gas was analyzed through an online IR gas analyzer, and hydrocarbons from C₁ to C₅ were analyzed through GC-FID. As a result of the experiment, the hydrogen yield tended to increase as the plasma power increased, and a maximum of 11.5% based on mass was obtained. On the other hand, carbon oxides such as CO and CO₂ were not generated. Along with hydrogen, the valuable by-products of this process are solid carbon and gaseous hydrocarbons. The solid carbon yields also increased up to 66% as the plasma power increased. On the other hand, the yield of gaseous hydrocarbons showed an opposite trend to that of hydrogen and carbon and consisted mainly of C₂ series (average content of 77%) and olefins (average fraction of 0.67). Consequently, it can be considered that the plasma thermal cracking is a promising technology for the CO₂-free hydrogen production, as well as solid carbon and C₂-olefin.

Sustainable and renewable energy technologies have attracted significant attention for reducing greenhouse emissions in the shift from fossil fuels. The production of green hydrogen from water electrolysis is considered an environmentally friendly strategy for a decarbonized economy. We examine the activities of the hydrogen and oxygen evolution reactions (HER and OER) using spin-coated thin-film electrodes with Pt/C and IrO₂ nano-electrocatalysts under acidic conditions. The nano-electrocatalysts are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The electrocatalytic activities of nanoscale Pt/C and IrO₂ are close to those of commercial Pt/C and superior to commercial IrO₂, resulting in improved overall water splitting performance. Furthermore, the OER kinetics analysis using the IrO₂ electrode is conducted using EIS measurements with distribution of relaxation time (DRT) analysis, resulting in a comparable exchange current density to that from the Tafel slope method (6.7 × 10⁻² mA/cm² versus 5.1 × 10⁻² mA/cm²), demonstrating the validity of the kinetics analysis. This work provides a general strategy for preparing novel and highly active OER electrode materials for water electrolysis.

Membrane separation is a promising, low-energy technology for purifying turquoise hydrogen from methane pyrolysis streams. However, there is a critical knowledge gap between the performance of membrane materials and the practical application of large-scale modules under realistic process conditions. This study evaluates commercial polyimide and polysulfone hollow fiber membranes for H₂/CH₄ separation. The effect of feed composition and pressure on the membrane separation performance were studied, revealing that the separation efficiency is overwhelmingly dominated by concentration polarization, which reduced the H₂/CH₄ separation factor by up to 80% compared to ideal values. Despite this, by optimizing process conditions, we successfully achieved a permeate purity of 99.3% H₂ at 85% recovery. Furthermore, Aspen Plus simulations of an integrated pyrolysis reactor with the membrane unit and a recycle stream demonstrate significant process benefits. The integration increased the H₂ production rate from 10.3 to 17.6 kmol/h and substantially reduced the specific energy consumption from 40.3 to 24.9 kJ/g H₂ compared to non-integrated systems. This work shows that a membrane process can improve not only the product H₂ purity but also the overall energy efficiency of a turquoise hydrogen production process.