(Invited) Electrochemical Processing of Metal-Insulator-Semiconductor (MIS) Photoelectrodes

Photoelectrochemical (PEC) water splitting is a promising route to solar-driven H₂ production, but the efficiency and stability of semiconducting photoelectrodes must be improved. One potential approach to achieving high efficiency and good electrochemical stability is the metal-insulator-semiconductor (MIS) photoelectrode design. [1-4] The MIS arrangement generally consists of catalytic metal structures, or collectors, deposited on an oxide-covered semiconductor as illustrated in Fig. 1. A crucial element of this design is the insulating oxide layer, which protects the semiconductor from the potentially corrosive electrolyte while facilitating minority carrier tunneling between the semiconductor and collectors. The oxide layer must be ultra-thin (1-3 nm) and exhibit minimal defects at the SiO₂/Si interface in order to facilitate efficient tunneling and maximize photovoltage.

            In this work, we have systematically investigated electrodeposition of Pt nanoparticle collectors on SiO₂-covered p-Si(100) MIS photoelectrodes, with the goal of obtaining a high degree of control of nanoparticle coverage, catalytic surface area, and nanoparticle size. These three parameters strongly influence photoelectrode optical, catalytic, and photovoltage performance, respectively, and electrodeposition offers an exciting opportunity to optimize these properties. This work has studied the influence of key deposition parameters (potential, current density, surface treatment) on the physical properties of the Pt nanoparticles, as well as the resulting PEC performance for photo-driven hydrogen evolution reaction (HER).  Through systematic investigation of the structure-property relationships in this MIS photoelectrode system, this study deconvolutes the optical, electronic, and catalytic influences of Pt nanoparticle geometries on photoelectrode performance. Such loss analysis is highly useful for guiding the design of more efficient photoelectrodes. Finally, opportunities and challenges of utilizing electrochemical processing for the manufacture of efficient photoelectrodes are discussed.        

References

1. H.J. Lewerenz, et al., Electrochem. Acta, 56, 10726 (2011).

2. A.G. Munoz and H.J. Lewerenz, ChemPhysChem, 11, 1603 (2010).

3. Y. Chen, P. McIntyre, et al., Nature Materials, 10, 539 (2011).

4. D.V. Esposito, I. Levin, T.P. Moffat, A.A. Talin, Nature Materials, 12, 562 (2013).