(Invited) On Solar Seawater Splitting
Authors: Vayssieres Lionel 
Published: August 2024

We are currently witnessing the widest worldwide environmental disasters and it is now crucial for the future of humanity to transition to novel societies where environmental, energy, and economic policies are no longer based on endless-growth financial models and fossil fuel technologies to decrease our environmental footprint. The origin of this strong imbalance between human activities and the environment is found in the endless-growth economic systems in place in major countries worldwide as it inherently requires the use of endless cheap energy to be sustained, hence the massive use of coal and fossil fuels as energy sources for a more profitable energy return on energy invested, which might be good for the economy but not for our environment, health, and sustainable future. Technological innovations have always helped boost the economy numerous times throughout civilizations yet it must involve large-scale, clean, and cost-effective fabrication techniques and be based on efficient earth-abundant and easily recyclable materials. A transition to hydrogen-based energy and economy is ideal as it produces zero carbon emission and hydrogen fuel cell and forthcoming hydrogen combustion transportation are available worldwide. However, most of the hydrogen produced comes from nonrenewable sources, i.e. by steam reforming of methane which produces very large amount of carbon mono/dioxide. The most natural, cleanest and sustainable way to produce hydrogen at large scale is by solar seawater splitting[1]. Our strategy is to fabricate earth-abundant and non-toxic devices consisting of oriented arrays of quantum rods/dots of high purity synthesized by aqueous chemical growth at low temperature without surfactant and with controlled dimensionalities and surface chemistry[2] with intermediate bands for high visible-light conversion, band structure edges optimized for stability against photocorrosion and operation conditions at neutral pH, low bias and no sacrificial agent. Such characteristics, combined with the in-depth investigation of their size dependent and interfacial electronic structure[3] and electrical properties[4] provide better fundamental understanding and structure-efficiency relationships for a cost-effective and sustainable generation of hydrogen from the two most abundant and geographically-balanced free resources available, the sun and seawater. An overview of such a strategy is presented for oxides, nitrides, sulfides as well as semiconductor-molecular catalysts hybrids[5], their low-cost and large scale fabrication, physical characterization, photogenerated charge dynamics, dopant segregation and thermal processing effects[1].
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