This paper reports the development of a high-performance photoanode device using atomically dispersed iridium (Ir) single atoms as catalysts for photoelectrochemical (PEC) water oxidation. The Ir single atoms are anchored on a NiO/Ni thin film deposited on n-type silicon, with a ZrO2 insulating layer enhancing photovoltage. The device exhibits a record-high PEC performance with a photocurrent density of 27.7 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE) and maintains stability for 130 h. Intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) reveal that the Ir single atoms effectively suppress charge recombination and boost charge transport. Density functional theory (DFT) calculations confirm that the Ir single atoms act as active catalytic centers, lowering the energy barrier for the potential-determining step in oxygen evolution reaction (OER).

Seung Eun Jun, Young Hun Kim, Jun Hyuk Kim, Woo Seok Choi, Sunghyun Choi, Ji Yeon, Hyeokjun Park, Soo Hyun Park, Kwang Chul Kim, Hae Lim, Soo Hyun Kim, Jooho Moon, Ho Won Jang