Boosting nitrogen adsorption for photocatalytic ammonia production via tuning electron distribution using zero valent iron as medium

Abstract

Photocatalytic nitrogen reduction to ammonia plays an important role in agricultural production and now-generation hydrogen storage technology. However, the practicality is limited by low efficiency owing to the poor charge-transfer rate and slow ammonification reactions. Herein, a ternary Fe2O3-Fe-HCNS composite is reported with all-solid-state Z-scheme heterojunction, which zero valent iron (ZVI) with abundant electrons is employed as conductor between hollow g-C3N4 sphere (HCNS) and Fe2O3. ZVI facilitates photogenerated electrons transfer and changes charge distribution on the Fe2O3-Fe-HCNS surface, thus an electron-rich region is formed around HCNS, which improves N2 adsorption and ammonification reaction on the HCNS surface. Moreover, the dual interfacial electric fields are established in the heterojunction, which can promote efficient separation and migration of photo-induced electrons and holes in space, leading to the good photocatalytic performances with the higher ammonia yield (296.30 μmol g−1h−1) and apparent quantum yield (1.38%, 400 nm) in neutral electrolytes. In addition, compared with the catalyst powder, vertical carbon paper supporting Fe2O3-Fe-HCNS catalyst can reduce secondary pollution and facilitate recycling.