Photoelectrochemical hydrogen generation using gradient-bandgap semiconductor arrays for improved solar energy conversion and water splitting efficiency
Opakhai S. Abed A.M. Mukhtar A. Abduvokhidov A. Madaminov B. Madaminov S.
18 August 2025Elsevier Ltd
International Journal of Hydrogen Energy
2025#159
Photoelectrochemical (PEC) water splitting offers a promising route for solar hydrogen production, but current systems suffer from limited light absorption, poor charge separation, and inadequate stability. This study aimed to develop a novel gradient-bandgap semiconductor array architecture to overcome these fundamental limitations and enhance solar-to-hydrogen (STH) conversion efficiency. Gradient-bandgap semiconductor arrays were fabricated via atomic layer deposition, creating sequential layers of TiO2, WO3, and BiVO4 with compositionally graded interfaces. XRD, HRTEM, XPS, and UV–vis spectroscopy provided photoelectrode characterization. Under simulated AM 1.5G illumination, the photoelectrochemical capabilities were assessed via intensity-modulated photocurrent spectroscopy, electrochemical impedance spectroscopy, incident photon-to-current efficiency, and current-voltage measurements. The gradient-bandgap architecture attained a STH conversion efficiency of 12.32 %, representing a 7.1-fold improvement over single-material BiVO4 photoelectrodes (1.73 %). Photocurrent density reached 16.78 mA/cm2 at 1.23 V versus reversible hydrogen electrode, with a corresponding hydrogen evolution rate of 6.21 mmol/h·cm2. The photoelectrode demonstrated exceptional stability, retaining 95.1 % of its initial performance after 200 h of continuous operation. Charge transfer efficiency reached 90.4 %, significantly higher than the 59.2–75.8 % observed in single-material electrodes, while carrier lifetime extended to 18.3 ns (39–115 % improvement over individual components). The gradient-bandgap semiconductor array design successfully addresses the critical limitations of conventional photoelectrodes through synergistic integration of complementary materials with engineered interfaces. This approach provides a practical pathway toward high-efficiency, durable, and economically viable solar hydrogen production without requiring expensive noble metal catalysts.
Bandgap engineering , Hydrogen generation , Photoelectrochemical , Solar energy , Water splitting
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Institute of Physics and Technical Science, L.N. Gumilyov Eurasian National University, Astana, 010000, Kazakhstan
Mechanical Power Technical Engineering Department, College of Engineering and Technologies, Al-Mustaqbal University, Babylon, 51001, Iraq
Al - Mustaqbal Center for Energy Research, Al-Mustaqbal University, Babylon, 51001, Iraq
Institute of Sustainable Energy, Putrajaya Campus, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, Kajang, 43000, Malaysia
New Uzbekistan University, Movarounnahr Street 1, Tashkent, 100000, Uzbekistan
Andijan State University, Universitet Str. 129, Andijan, 170100, Uzbekistan
Mamun University, Bolkhovuz Street 2, Khiva, 220900, Uzbekistan
Urgench State University, Urgench, 220100, Uzbekistan
Institute of Physics and Technical Science
Mechanical Power Technical Engineering Department
Al - Mustaqbal Center for Energy Research
Institute of Sustainable Energy
New Uzbekistan University
Andijan State University
Mamun University
Urgench State University
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