InGaN-based heterostructures for solar water splitting with various mechanisms of photogenerated carrier separation

Abstract

In this study, we present a photocatalytic application based on three distinct types of three-dimensional (3D) nitride heterostructures: self-assembled core–shell InGaN/GaN microrods, 3D semipolar InxGa1−xN/InyGa1−yN multiple quantum wells, and nanopyramids featuring an InzGa1−zN/InwGa1−wN multilayer periodic structure. These InGaN-based architectures utilize different mechanisms of photogenerated carrier separation, arising from their specific geometric and band profile designs. The structural and optical properties of the fabricated InGaN-based heterostructures were systematically characterized using scanning electron microscopy, photoluminescence, and cathodoluminescence, followed by a comparative evaluation of their photocatalytic hydrogen (H2) evolution performance in a batch photoreactor. H2 was detected as the sole product of the photocatalytic decomposition of a methanol–water solution. The stability of the photocatalyst was verified through repeated use of the same batch, yielding consistent results. Our results demonstrate that the photocatalytic activity of InGaN-based heterostructures strongly dependents on material quality, particularly the suppression of the non-radiative recombination of photogenerated carriers. We propose different carrier separation mechanisms in each structure type and compare their photocatalytic efficiencies. The best results were achieved with the InzGa1−zN/InwGa1−wN multilayer periodic structure. This highlights the benefits of integrating polarization-field engineering with nanostructured architectures for photocatalytic H2 production. This study shows that optimizing carrier separation through band engineering and nanostructure design can significantly improve the performance of InGaN-based photocatalysts.