Researchers at the Institute for Advanced Studies in Basic Sciences (IASBS) in Zanjan, in collaboration with scientists from the Polytechnic University of Valencia, have succeeded in designing a magnetic nanocomposite capable of converting the highly toxic gas H₂S into hydrogen with high efficiency.
According to the report, In this study, a novel p–n junction structure was constructed from two semiconductors, CoMn₂O₄ and MgFe₂O₄, and its photocatalytic performance and magnetic properties were significantly enhanced by incorporating carbon nanotubes (CNTs). The presence of CNTs reduced electron–hole recombination, facilitated charge transfer, and increased the active surface area of the material, ultimately boosting hydrogen production efficiency by approximately 60%. This achievement offers a low-cost and environmentally friendly pathway for converting hazardous substances into clean fuel.
The conversion of dangerous pollutants into valuable energy resources has become one of the key challenges attracting the attention of energy and environmental researchers in recent decades. Hydrogen sulfide (H₂S), which is generated in oil and gas industries, wastewater treatment plants, and chemical processes, is among the most toxic, corrosive, and environmentally threatening pollutants. Managing this gas is costly and complex; however, if decomposed and converted in a controlled manner, it can serve as a source of hydrogen—one of the cleanest and most versatile energy carriers. This dual nature underscores the growing need to develop innovative technologies for the treatment and recycling of H₂S.
In this context, researchers from IASBS, in collaboration with a team from the Polytechnic University of Valencia and the Spanish National Research Council (CSIC), have developed a completely new photocatalytic material with a nanostructured architecture and magnetic properties that exhibits outstanding performance in converting H₂S into hydrogen under light irradiation. The research aims to establish a low-cost, sustainable, and scalable route for hydrogen production. The findings demonstrate that by relying on earth-abundant materials and nanotechnology, an effective and industrially viable solution to this challenge can be achieved.
The core innovation of this work lies in the fabrication of a magnetic nanocomposite based on a p–n junction formed between two semiconductors: CoMn₂O₄ as a p-type semiconductor and MgFe₂O₄ as an n-type semiconductor. Creating a p–n junction at the nanoscale enables more efficient separation of photogenerated electrons and holes and prevents their rapid recombination. Electron–hole recombination is one of the main obstacles to improving photocatalyst efficiency, and controlling it is a central focus of nano-energy research.
A major turning point in the study came with the incorporation of carbon nanotubes (CNTs) to further enhance the performance of this structure. The presence of CNTs produced several simultaneous effects: a significant increase in active surface area, the creation of fast conductive pathways for charge transport, and improved separation of electron–hole pairs. Together, these factors led to a much more efficient conversion of H₂S into hydrogen.
According to the reported results, the highest hydrogen production was achieved in composites with a p-to-n semiconductor molar ratio of 1:2. The addition of CNTs increased hydrogen production efficiency by about 60% compared with CNT-free samples—a remarkable improvement relative to conventional photocatalysts. Spectroscopic analyses such as EPR, photoluminescence (PL) decay, along with photocurrent and impedance measurements, confirmed that CNTs reduce electron–hole recombination rates and enhance charge storage and transfer capabilities.
Another important operational feature of this nanocomposite is its magnetic property, which allows the photocatalyst to be easily collected and recycled using a simple magnetic field after the reaction. In industrial applications, where large material volumes and separation costs are critical concerns, this advantage can play a decisive role in the economic feasibility of the process. Results from VSM tests and XPS analyses further confirmed that CNTs improve not only the optical performance but also the magnetic behavior of the composite.
Transmission electron microscopy (TEM) observations also verified the existence of a genuine p–n junction between the phases at the atomic scale, demonstrating that the designed structure was formed exactly as intended and that the enhanced performance originates from precise nanostructure engineering.
Overall, this research outlines a new pathway for the design of next-generation photocatalytic materials, materials that, using earth-abundant elements and nanotechnology, can convert hazardous pollutants into clean energy carriers. The integration of optical, electrical, and magnetic properties into a single, scalable structure could pave the way for the development of industrial solar reactors that both reduce the environmental footprint of industries and contribute to a hydrogen-based economy.
The findings of this research team indicate that adding carbon nanotubes to a magnetic p–n junction-based photocatalyst goes far beyond a simple modification. It effectively creates a multifunctional nanoplatform that enhances reactivity, improves charge separation, increases active surface area, and enables rapid recovery. Such structures can form the basis of a new generation of clean energy materials for hydrogen production, pollutant remediation, and the advancement of solar energy technologies.
The results of this project have been published in an article entitled “Highly effective CNT-based magnetic p–n junction nanocomposite photocatalyst/solar-energy material for hazmat conversion to hydrogen fuel” in the journal Composites Part B: Engineering.