Nickel Hydroxide Catalyzed Bias‐free Photoelectrochemical NH<sub>3</sub> Production via Nitrate Reduction
Wonjoo Jin, Hyunju Go, Juyeon Jeong, Jeonghwan Park, Ahmad Tayyebi, Je Min Yu, Seungchul Kim, Keunsu Choi, Ji‐Wook Jang, Kwanyong Seo
Abstract
Abstract The photoelectrochemical nitrate reduction reaction (PEC NO 3 RR) potentially converts nitrate, a major water pollutant, into NH 3 , which is an eco‐friendly, next‐generation energy source. However, achieving high efficiency in the PEC NO 3 RR has been challenging because of the need for high applied voltage and competition with the hydrogen evolution reaction (HER). In this study, a PEC NO 3 RR is successfully implemented that demonstrated a high NH 3 production rate of 2468 µg cm −2 h −1 (at −0.1 V vs RHE) using a c‐ Si photocathode with Ni foil as the catalyst. Conducting the PEC NO 3 RR under alkaline conditions can lead to the self‐activation of the Ni surface with Ni(OH) 2 . Ni(OH) 2 can suppress the competitive HER and facilitate NO 3 RR, enhancing NH 3 production efficiency. Furthermore, a PEC NO 3 RR system is developed that operates without external voltage and achieved bias‐free record‐high solar to NH 3 conversion efficiency of 3.8% and an NH 3 production rate of 554 µg cm −2 h −1 .