Modulation of surface bonding topology: oxygen bridges on OH-Terminated InP (001)

An understanding and control of complex physiochemical processes at the photoelectrode/electrolyte interface in photoelectrochemical cells (PECs) are essential for developing advanced solar-driven water-splitting technology. Here, we integrate ambient pressure X-ray photoelectron spectroscopy (APXPS) and high-level first-principles calculations to elucidate the evolution of the H2O/InP (001) interfacial chemistry under in situ and ambient conditions. In addition to molecular H2O, OH and H are the only two species found on InP (001) at room temperature. Under elevated temperatures, although the formation of In–O–P is thermodynamically more favorable over In–O–In, the latter can be preferentially generated in a kinetically driven and nonequilibrated environment such as ultrahigh vacuum (UHV); however, when InP is exposed to H2O at both elevated pressures and temperatures, its surface chemistry becomes thermodynamically driven and only In–O–P (or POx) oxygen bridges form. Our simulations suggest that In–O–In, rather than In–O–P, constitutes a charge carrier (hole) trap that causes photocorrosion in PEC devices. Therefore, understanding and modulating the chemical nature of oxygen bridges at the H2O/InP (001) interface will shed light on the fabrication of InP-based photoelectrodes with simultaneously enhanced stability and efficiency.