Physical Modeling of Photoelectrochemical Hydrogen Production Devices

Abstract

Solar-powered water splitting with photoelectrochemical (PEC) devices is a promising method to simultaneously harvest and store solar energy at a large scale. Highly efficient small prototype PEC devices reported recently demonstrate a move from basic material research towards design and engineering of complete devices and systems. The increased interest in engineering calls for better understanding about the operational details of PEC devices at different length scales. The relevant physical phenomena and the properties of typical materials are well known for separate device components, but their interaction in a complete PEC cell has received less attention. Coupled physical models are useful for studying these interactions and understanding the device operation as a whole, and for optimizing the devices. We review the central physical processes in solar-powered water splitting cells and the physical models used in their theoretical simulations. Our focus is in particular on how different physical processes have been coupled together to construct device models, and how different electrode and device geometries have been taken into account in them. Reflecting on the literature we discuss future opportunities and challenges in the modeling of PEC cells.3

Membrane-less photoelectrochemical cells: product separation by hydrodynamic control

“…A recent review 28 discusses the uses and limitations of the transfer matrix method in more detail, but in brief it is used in this work as it can take into account multiple reflections and determine the parasitic absorption losses by the glass, electrolyte and other PEC components. For light incident normal to the layers, the type of polarisation of the light does not affect the transmittance, reflectance and absorptance.…”

“…In order to achieve a more accurate optical model, the electromagnetic wave propagation through the nano-structure would have to be calculated by solution of Maxwell's equations 28 .…”

“…Kemppainen et al 28 have produced an extensive review on modelling PEC reactors and there are examples that range from fundamental models of charge transport in the semiconductor 29,30 and both semiconductor and electrolyte 31 , to large scale models of devices 13,26,32,33 . Crucially, all the large scale device models (with the exception of Jin et al 17 ) included a membrane for product separation and hence the theoretical benefits of applying membrane-less electrolyser research to PEC systems have not been assessed.…”

Impedance Spectra and Surface Coverages Simulated Directly from the Electrochemical Reaction Mechanism: A Nonlinear State-Space Approach

“…These studies allow to predict the overall performance of the cells under given operating conditions and consider the semiconductor properties, such as carrier generation, charge transport, recombination, charge transfer, band bending, and the Helmholtz layer 4,[34][35][36][37] .…”

Mass transport aspects of electrochemical solar-hydrogen generation

“…As multiple comprehensive reviews on semiconductor materials for solar water-splitting have been recently published in the literature, 6,14-19 we will limit this section to a summary of the processes taking place within this component. 16,20 The propagation of the irradiated light toward and within the semiconductor is described by Maxwell's equations. The absorbed energy and the optical quantum yield define the rate of the charge carrier pair density generation.…”