Lateral silicon oxide/gold interfaces enhance the rate of electrochemical hydrogen evolution reaction in alkaline media

Abstract

The production of solar hydrogen with a silicon based water splitting device is a promising future technology, and silicon-based metal–insulator–semiconductor (MIS) electrodes have been proposed as suitable architectures for efficient photocathodes based on the electronic properties of the MIS structures and the catalytic properties of the metals. In this paper, we demonstrate that the interfaces between the metal and oxide of laterally patterned MIS electrodes may strongly enhance the catalytic activity of the electrode compared to bulk metal surfaces. The employed electrodes consist of well-defined, large-area arrays of gold structures of various mesoscopic sizes embedded in a silicon oxide support on silicon. We demonstrate that the activity of these electrodes for hydrogen evolution reaction (HER) increases with an increase in gold/silicon oxide boundary length in both acidic and alkaline media, although the enhancement of the HER rate in alkaline electrolytes is considerably larger than in acidic electrolytes. Electrodes with the largest interfacial length of gold/silicon oxide exhibited a 10-times larger HER rate in alkaline electrolytes than those with the smallest interfacial length. The data suggest that at the metal/silicon oxide boundaries, alkaline HER is enhanced through a bifunctional mechanism, which we tentatively relate to the laterally structured electrode geometry and to positive charges present in silicon oxide: Both properties change locally the interfacial electric field at the gold/silicon oxide boundary, which, in turn, facilitates a faster transport of hydroxide ions away from the electrode/electrolyte interface in alkaline solution. This mechanism boosts the alkaline HER activity of p-type silicon based photoelectrodes close to their HER activity in acidic electrolytes.

Gold–Rhodium Nanoflowers for the Plasmon-Enhanced Hydrogen Evolution Reaction under Visible Light

“…Since water should now be considered, it is also important to highlight that the water adsorption conformation affects the way the O–H bond will be more or less easily broken during the Volmer step . The electrochemical activity dependence on the water adsorption conformation is not new; actually, it was already proposed by Trasatti for the HER, and it has been shown in the literature that it can affect the electrochemical activity for different reactions. − Therefore, it is proposed that the water structure orientation at the double-layer region will give insights into investigations on the HER mechanisms …”

Silica Support Affects the Catalytic Hydrogen Evolution by Silver

“…These effects were often associated with the reducibility of the central metal in the metal‐oxide supports [22,28] . However, recently, such effects were also reported for irreducible oxides like silica supports [29,30] …”

Electrochemical Activation of Silicon: Enhancing Hydrogen Production from FeNi Electrocatalysts

“…3 Si is an attractive material to develop PEC water splitting devices using a metal−insulator−semiconductor (MIS) photoelectrode architecture. 4 However, Sibased photo-electrodes are unstable in alkaline solution. 2,4,5 Therefore, a challenge that silicon-based PEC electrodes must overcome is the corrosion of the oxide layer under electrochemical conditions (pH and potentials).…”

“…4 However, Sibased photo-electrodes are unstable in alkaline solution. 2,4,5 Therefore, a challenge that silicon-based PEC electrodes must overcome is the corrosion of the oxide layer under electrochemical conditions (pH and potentials). 4,6 This corrosion behavior, however, can be used advantageously in an alternative approach to hydrogen production through the self-oxidation of the electrode material.…”

“…2,4,5 Therefore, a challenge that silicon-based PEC electrodes must overcome is the corrosion of the oxide layer under electrochemical conditions (pH and potentials). 4,6 This corrosion behavior, however, can be used advantageously in an alternative approach to hydrogen production through the self-oxidation of the electrode material. The on-demand production of hydrogen without light, heat, or electricity has been demonstrated through the spontaneous reaction of silicon with water.…”