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Abstract Cu₂O has been successfully synthesized in different morphologies/sizes (nanoparticles and octahedrons) via a low-temperature chemical reduction method. Trapping metal ions in an ice cube and letting them slowly melt in a reducing agent solution is the simplest way to control the nanostructure. Enhancement of charge transfer and transportation of ions by Cu₂O nanoparticles was shown by cyclic voltammetry and electrochemical impedance spectroscopy measurements. In addition, nanoparticles exhibited higher current densities, the lowest onset potential, and the Tafel slope than others. The Cu₂O electrocatalyst (nanoparticles) demonstrated the Faraday efficiencies (FEs) of CO, CH₄, and C₂H₆up to 11.90, 76.61, and 1.87%, respectively, at −0.30 V versus reference hydrogen electrode, which was relatively higher FEs than other morphologies/sizes. It is mainly attributed to nano-sized, more active sites and oxygen vacancy. In addition, it demonstrated stability over 11 h without any decay of current density. The mechanism related to morphology tuning and electrochemical CO₂reduction reaction was explained. This work provides a possible way to fabricate the different morphologies/sizes of Cu₂O at low-temperature chemical reduction methods for obtaining the CO, CH_4,and C₂H₆products from CO₂ 

Cerium oxide (CeO₂) photo/electrocatalysts for energy storage and environmental applications have attracted considerable interest because of stable crystal structure, low toxicity/cost, superior chemical stability, stable redox (Ce³⁺/Ce⁴⁺) pairs, abundant oxygen defects, and capablility for intense interaction with other materials. However, the wide bandgap and poor conductivity lower the CeO₂photo/electrocatalytic and energy storage performances. To overcome these limitations, various modification strategies (tuning morphology, doping or loading of metal nanoparticles, and heterostructures) have been applied for the improvement of photocatalytic (removal of organic contaminants from water/wastewater and H₂production and CO₂reduction reactions) efficiency, electrocatalytic (hydrogen/oxygen evolution reactions and CO₂reduction reactions), and energy storage performances (supercapacitor) of CeO₂‐based materials. Herein, the recent progress of CeO₂‐based materials for electro(photo)catalysis and energy storage applications has been discussed. The challenges and possible direction of CeO₂‐based materials for electro(photo)catalysis and energy storage applications have been emphasized. Furthermore, this comprehensive review is expected to advance the design of CeO₂‐based materials and their applications in electro(photo)catalysis and energy.