Photoelectrochemical Nitrogen Reduction to Ammonia on Cupric and Cuprous Oxide Photocathodes
Youn Jeong Jang, A. Lindberg, Margaret A. Lumley, Kyoung‐Shin Choi
Abstract
Photoelectrochemical N<sub>2</sub> reduction enables the production of NH<sub>3</sub> under ambient conditions using water as the hydrogen source. Furthermore, by utilizing solar energy, photoelectrochemical N<sub>2</sub> reduction can significantly reduce the energy input required for N<sub>2</sub> reduction. In this study, photoelectrochemical N<sub>2</sub> production was investigated using CuO and Cu<sub>2</sub>O photocathodes that are known to be poorly catalytic for water reduction, the major reaction competing with N<sub>2</sub> reduction. When tested under simulated solar illumination with isotopically labeled <sup>15</sup>N<sub>2</sub> in 0.1 M KOH solution, the CuO and Cu<sub>2</sub>O photocathodes produced <sup>15</sup>NH<sub>3</sub> with a Faradaic efficiency of 17% and 20% at 0.6 V and 0.4 V vs. RHE, respectively. These potentials are significantly more positive than the thermodynamic reduction potential of N<sub>2</sub>, which demonstrates how the use of photoexcited electrons in the CuO and Cu<sub>2</sub>O photocathodes can reduce the energy input required for NH<sub>3</sub> production. Here, the use of photoexcited electrons in these photocathodes for N<sub>2</sub> reduction, water reduction, and photocorrosion was carefully examined.