Photoelectrocatalytic $N_2$ fixation and C-H oxyfunctionalization driven by $H_2O$ oxidation

Abstract

Solar-driven $N_2$ fixation offers a green alternative to the highly energy intensive Haber-Bosch process that releases more than 300 million metric tons of $CO_2$ annually to form $NH_3$. However, current $N_2$-reducing photoelectrochemical (PEC) studies have not elucidated how the oxidation reaction affects the $N_2$ reduction reaction (NRR) and how to the corresponding anodic half reactions. Herein, this thesis reports a bias-free PEC platform for simultaneous $N_2$ reduction to $NH_3$ and $H_2O$ oxidation to $O_2$ and/or $H_2O_2$. Mo-doped bismuth vanadate-based photoanodes extract electrons from $H_2O$ and transfer them to the photoelectrocatalytic NRR site. A silicon photovoltaic-wired hematite photocathode receives the electrons to drive the NRR, which is influenced by conditions of the $H_2O$ oxidation reaction site. Furthermore, the integration of PEC $N_2$ reduction with $H_2O_2$-dependent biocatalytic oxyfunctionalization achieves simultaneous synthesis of valuable fuels and compounds on both electrodes. This thesis presents the first example of a PEC NRR platform coupled with $H_2O$ oxidation and $H_2O_2$-dependent oxygenation for unbiased chemical synthesis using $N_2$, $H_2O$, and sunlight.