Graphitic carbon nitride (g-C₃N₄) has become an important material because of its attractive optoelectronic properties. It has been applied in various fields such as photovoltaics, biosensing, and photocatalysis. As an analog of graphene, it has layers which can be transformed into different morphologies including nanosheets, nanotubes, and quantum dots. Pristine g-C₃N₄ exhibits a low specific surface area and a high rate of recombination of photogenerated charges. Therefore, modification is required in order to improve its properties, for instance, by doping it with other atoms and transforming it into another morphology. In this review, the synthesis, modifications, and applications of g-C₃N₄ are evaluated. The use of theoretical strategies to understand various properties of g-C₃N₄ and its composites is highlighted. Moreover, the current status on the application of g-C₃N₄ is explored. Ultimately, this review will shed more light on the uses and modifications of g-C₃N₄ for future applications.

Recently, the recovery of metals extracted from the spent membrane electrode assemblies (MEAs) of fuel cells has attracted significant scientific attention due to its detrimental environmental impacts. Two major approaches, i.e., pyrometallurgical and hydrometallurgical, have been explored to recover platinum group metals (PMGs) from used proton exchange membrane fuel cells (PEMFCs). However, the efficacy of these methods has been limited by the low concentrations of the metals and the high costs involved. Essentially, pyrometallurgical processes result in the evolution of harmful gases. Thus, the hydrometallurgical process is preferred as a suitable alternative. In this review, an overview of the application of pyrometallurgical and hydrometallurgical methods in the recovery of PGMs is presented. The health risks, benefits, and limitations of these processes are highlighted. Finally, the hurdles faced by, opportunities for, and future directions of these approaches are identified. It is envisaged that this review will shed light on the current status of processes for the recovery of spent PGMs and propel their advancement for effective recycling strategies.

Perovskite solar cells (PSCs) are regarded as extremely efficient and have significant potential for upcoming photovoltaic technologies due to their excellent optoelectronic properties. However, a few obstacles, which include the instability and high costs of production of lead-based PSCs, hinder their commercialization. In this study, the performance of a solar cell with a configuration of FTO/CdS/BaZrS₃/HTL/Ir was optimized by varying the thickness of the perovskite layer, the hole transport layer, the temperature, the electron transport layer (ETL)’s defect density, the absorber defect density, the energy band, and the work function for back contact. Various hole transport layers (HTLs), including Cu₂O, CuSCN, P3HT, and PEDOT:PSS, were assessed to select the best materials that would achieve high performance and stability in PSC devices. At optimal levels, PEDOT:PSS reached a maximum power conversion efficiency (PCE) of 18.50%, while P3HT, CuSCN, and Cu₂O exhibited a PCE of 5.81, 10.73, and 9.80%, respectively. The high performance exhibited by PEDOT:PSS was attributed to better band alignment between the absorber and the PEDOT:PSS, and, thus, a low recombination of photogenerated charges. The other photovoltaic parameters for the best device were a short-circuit current density (J_sc) of 23.46 mA cm⁻², an open-circuit voltage (V_oc) of 8.86 (V), and a fill factor (FF) of 8.90%. This study highlights the potential of chalcogenide-based PSCs as an efficient and stable alternative to traditional lead-based solar cells, with successful optimization paving the way for future research on eco-friendly materials and scalable production methods.