Croatia
Hydrogen Production Through Newly Developed Photocatalytic Nanostructures and Composite Materials
Jun 2025
Publication
Photocatalytic hydrogen (H2) production offers a promising solution to energy shortages and environmental challenges by converting solar energy into chemical energy. Hydrogen as a versatile energy carrier can be generated through photocatalysis under sunlight or via electrolysis powered by solar or wind energy. However the advancement of photocatalysis is hindered by the limited availability of effective visible light-responsive semiconductors and the challenges of charge separation and transport. To address these issues researchers are focusing on the development of novel nanostructured semiconductors and composite materials that can enhance photocatalytic performance. In this paper we provide an overview of the advanced photocatalytic materials prepared so far that can be activated by sunlight and their efficiency in H2 production. One of the key strategies in this research area concerns improving the separation and transfer of electron–hole pairs generated by light which can significantly boost H2 production. Advanced hybrid materials such as organic–inorganic hybrid composites consisting of a combination of polymers with metal oxide photocatalysts and the creation of heterojunctions are seen as effective methods to improve charge separation and interfacial interactions. The development of Schottky heterojunctions Z-type heterojunctions p–n heterojunctions from nanostructures and the incorporation of nonmetallic atoms have proven to reduce photocorrosion and enhance photocatalytic efficiency. Despite these advancements designing efficient semiconductor-based heterojunctions at the atomic scale remains a significant challenge for the realization of large-scale photocatalytic H2 production. In this review state-of-the-art advancements in photocatalytic hydrogen production are presented and discussed in detail with a focus on photocatalytic nanostructures heterojunctions and hybrid composites.
Advanced Analytical Modeling of Polytropic Gas Flow in Pipelines: Unifying Flow Regimes for Efficient Energy Transport
Oct 2025
Publication
In the present work a new analytical model of polytropic flow in constant-diameter pipelines is developed to accurately describe the flow of compressible gases including natural gas and hydrogen explicitly accounting for heat exchange between the fluid and the environment. In contrast to conventional models that assume isothermal or adiabatic conditions the proposed model simultaneously accounts for variations in pressure temperature density and entropy i.e. it is based on a realistic polytropic gas flow formulation. A system of differential equations is established incorporating the momentum continuity energy and state equations of the gas. An implicit closed-form solution for the specific volume along the pipeline axis is then derived. The model is universal and allows the derivation of special cases such as adiabatic isothermal and isentropic flows. Numerical simulations demonstrate the influence of heat flow on the variation in specific volume highlighting the critical role of heat exchange under real conditions for the optimization and design of energy systems. It is shown that achieving isentropic flow would require the continuous removal of frictional heat which is not practically feasible. The proposed model therefore provides a clear reproducible and easily visualized framework for analyzing gas flows in pipelines offering valuable support for engineering design and education. In addition a unified sensitivity analysis of the analytical solutions has been developed enabling systematic evaluation of parameter influence across the subsonic near-critical and heated flow regimes.
No more items...