Reverse water–gas shift chemical looping (RWGS-CL) offers a promising means of converting the greenhouse gas of CO₂ to CO because of its relatively low operating temperatures and high CO selectivity without any side product. This paper introduces a core–shell structured oxygen carrier for RWGS-CL. The prepared oxygen carrier consists of a metal oxide core and perovskite shell, which was confirmed by inductively coupled plasma mass spectroscopy (ICP-MS), XPS, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements. The perovskite-structured shell of the prepared oxygen carrier facilitates the formation and consumption of oxygen defects in the metal oxide core during H₂-CO₂ redox looping cycles. As a result, amounts of CO produced per unit weight of the core–shell structured oxygen carriers were higher than that of a simple perovskite oxygen carrier. Of the metal oxide cores tested, CeO₂, NiO, Co₃O₄, and Co₃O₄-NiO, La_0.75Sr_0.25FeO₃-encapsulated Co₃O₄-NiO was found to be the most promising oxygen carrier for RWGS-CL, because it was most productive in terms of CO production and exhibited long-term stability.

Although steam methane reforming (CH₄ + 2H₂O → 4H₂ + CO₂) is the most commercialized process for producing hydrogen from methane, more than 10 kg of carbon dioxide is emitted to produce 1 kg of hydrogen. Methane pyrolysis (CH₄ → 2H₂ + C) has attracted much attention as an alternative to steam methane reforming because the co-product of hydrogen is solid carbon. In this study, the simultaneous production of hydrogen and separable solid carbon from methane was experimentally achieved in a bubble column filled with molten potassium chloride. The melt acted as a carbon-separating agent and as a pyrolytic catalyst, and enabled 40 h of continuous running without catalytic deactivation with an apparent activation energy of 277 kJ/mole. The resultant solid was purified by water washing or acid washing, or heating at high temperature to remove salt residues from the carbon. Heating the solid product at 1200 °C produced the highest purity carbon (97.2 at%). The economic feasibility of methane pyrolysis was evaluated by varying key parameters, that is, melt loss, melt price, and carbon revenue. Given a potassium chloride loss of 0.45 per kg of produced carbon. In this case, methane pyrolysis using molten potassium chloride may be comparable to steam methane reforming with carbon capture storage.

Energy consumption and environmental pollution are major issues faced by the world. The present study introduces a single solution using SnS₂ for these two major global problems. SnS₂ nanoparticles and thin films were explored as an adsorbent to remove organic toxic materials (Rhodamine B (RhB)) from water and an alternative to the toxic cadmium sulfide (CdS) buffer for thin-film solar cells, respectively. Primary characterization tools such as X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), and UV-Vis-NIR spectroscopy were used to analyze the SnS₂ nanoparticles and thin films. At a reaction time of 180 min, 0.4 g/L of SnS₂ nanoparticles showed the highest adsorption capacity of 85% for RhB (10 ppm), indicating that SnS₂ is an appropriate adsorbent. The fabricated Cu(In,Ga)Se₂ (CIGS) device with SnS₂ as a buffer showed a conversion efficiency (~5.1%) close to that (~7.5%) of a device fabricated with the conventional CdS buffer, suggesting that SnS₂ has potential as an alternative buffer.