High Performance and Stability of Micropatterned Oxide-Passivated Photoanodes with Local Catalysts for Photoelectrochemical Water Splitting

A new passivation strategy for an oxygen evolving Si photoanode for efficient and stable photoelectrochemical (PEC) water splitting is presented. In our Si photoanode structure, to eliminate the Si/water interface, the Si is stabilized with a thick insulating and chemically inert SiO₂ film and locally defined electrocatalysts on the Si surface. The stabilized p⁺n-Si photoanode with SiO₂ film and micropatterned Ni catalysts produced photocurrent densities of 27 mA cm^–2 at water oxidation potential without corrosion for 24 h under water oxidation conditions. In addition, we provide a device modeling of our Si cell, i.e., an integrated photovoltaics–electrolyzer cell, to quantitatively assess the interplay between optical shadowing and catalytic performance, as a function of the coverage and characteristics of electrocatalysts on the water oxidation reaction during PEC water splitting. Design principles for high performance oxygen evolving Si photoanodes are presented based on the device modeling