Green hydrogen: solar-powered photochemical water splitting on InGaN nanowire arrays

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The global energy is on the cusp of immense change, and it has been projected by many that the emerging Hydrogen Economy may eventually replace the Carbon Economy that fuelled the industry revolution. In this regard, photochemical water splitting has been intensively investigated, which enables the direct conversion of solar energy into hydrogen based fuel. Over the past four decades, the development of photocatalysis has primarily focused upon large bandgap metal oxides employed in the form of powders. However, this oxide based approach suffers from two fundamental efficiency bottlenecks: weak photon absorption and poor exciton separation, due to the inherently large band gap of oxides and the limited surface area of powdered structures, respectively. In this project, the authors propose to investigate the photochemical water splitting on InGaN nanowire arrays, that can lead to high efficiency solar-to-hydrogen conversion. Compared to metal oxides, the energy bandgap of InGaN can encompass nearly the entire solar spectrum by varying the alloy compositions. Moreover, nanowires exhibit extremely large surface-to-volume ratios, significantly enhanced light absorption, and more efficient charge separation, promising drastically enhanced photocatalytic activity. The authors have recently achieved, for the first time in the world, photocatalytic overall water splitting and hydrogen generation using metal-nitride nanowires. In this project, the authors will further develop superior quality, multi-junction InGaN nanowire based photocatalysts that can absorb a large part of the solar spectrum and can drive high-efficiency(>15%) hydrogen generation under solar irradiation. By addressing the grand challenges for achieving stable, efficient water splitting and hydrogen generation directly from solar irradiation, this project will provide a paradigm shift in the rapidly evolving solar energy and hydrogen industries.