Efficiency Definition for Benchmarking

For direct solar-to-hydrogen processes, STH efficiency is defined as chemical energy of the hydrogen produced divided by solar energy input from sunlight incident on the process. The chemical energy of the hydrogen produced can be 

Equation (2.1) calculates the power output (numerator) based on the direct measurement of the true H2 production rate by an analytical method such as gas chromatography or mass spectrometry Alternatively, Equation (2.2) uses the relation that power is the product of voltage, current, and the Faradaic efficiency 

It is critical to note thatEqs. (2.1) and (2.2) are valid if and only if oat confirms stoichiometric gas evolution (H2 and O2) in the absence of any sacrificial electron donors or acceptors. Equation (2.2) similarly restricts the measured photocurrent 

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