Forty years after the first reported photoelectrochemical (PEC) water splitting experiment, commercial hydrogen production from PEC is still a dream. Thousands of papers later and no semiconductor system has been identified that has the potential for economical hydrogen production from PEC water splitting. The majority of the past research has been directed at metal oxides due to their expected low costs, ease of synthesis and stability. Little progress has been made; efficiencies for these oxide systems are abysmally low, primarily due to poor electronic structure. Recent technoeconomic analysis studies indicate that a 20% solar-to-hydrogen PEC conversion efficiency is necessary for a commercially viable system. Additional requirements of lifetime (years), and cells costs (&lt;$400/m2) make a working device extremely challenging. To achieve such high efficiencies, semiconductors with superior electronic properties are required as well as high efficiency catalysts. Clearly then one must decide whether to use an existing PV-based semiconductor or search for a new semiconductor with the necessary electronic properties. The III-V-based solar cells show the highest solar PV efficiency and thus are excellent candidates for a PEC system. In fact, the highest solar-to-hydrogen efficiency to-date for PEC water splitting using visible light is the III-V tandem cell system with a published efficiency of 16%, but cell costs are high and lifetime is low. On the other hand, multi-component transition metal oxides are complex materials, making intuitive guesses difficult and a focused search very challenging. A computational approach that will narrow the composition space could greatly decrease the time it takes leading towards a successful material. This presentation will discuss some of the challenges and opportunities facing PEC community in our search for a workable PEC solar water-splitting system that could lead to a commercial device. The discussion will include metal oxides, surface treatments and tandem cells for PEC water splitting.

Challenges in photoelectrochemical water splitting

256th National Meeting (2018)

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