This decade is experiencing the widest consequences of man-made activities with environmental disasters at a record high including staggering air and water pollution due to toxic gases, chemicals, and ultrafine particles from industry, agriculture, and transportation sectors has become one of the most important problem that humanity is facing. It is now crucial to transition to new societies where environmental, energy, and economic policies are no longer based on endless-growth financial models and fossil fuel technologies to substantially decrease our environmental footprint and health impacts. The origin of this strong imbalance between human activities and the environment could be found in the endless-growth economic system 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 clearly is not for our environment, health, and sustainable future. Technological innovation has always helped boost the economy and has done it successfully numerous times throughout civilizations yet it must involve large-scale, clean, and cost-effective fabrication techniques and be based on highly efficient materials made of earth-abundant elements, easily extractable and recyclable rather than expensive, scarce, and toxic ones. In addition, it is crucial to develop novel (multi)functional materials where bulk limitations are overcome by changing the fundamental underlying physics and chemistry by quantum design.

The transition to hydrogen-based energy and economy would be ideal as it produces zero carbon emission and hydrogen fuel cell powered cars and public transportations are now available worldwide. However, most of the hydrogen produced still comes from nonrenewable sources, made by steam reforming of methane which produces large amount of carbon dioxide. The most natural, cleanest and sustainable way to produce hydrogen at large scale is by photocatalytically splitting seawater[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, bandgap and band edges optimized for stability against photocorrosion and operation conditions at neutral pH and low bias without sacrificial agent[1]. 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 the latest advances of such a strategy will be presented including native and doped oxides, nitrides, and sulfides[1] and hybrids consisting of visible-light-active semiconductors and molecular co-catalysts[5] and their characterization.

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