Artificial Photosynthesis of Ammonia by Semiconducting Plasmonic NIR Energy

Abstract

Artificial photosynthesis of ammonia is one of the most promising paths toward carbon neutrality and sustainability. However, nitrogen photo-fixation to produce ammonia in ultrapure water is still challenging due to the thermodynamic and kinetic requirements of the nitrogen reduction reaction. An ideal photocatalyst is expected to have energetic electrons to drive the nitrogen reduction reaction, as well as enough affinity for chemisorption and activation of nitrogen molecules at the surface. Compared with plasmonic metal catalysts, plasmonic semiconducting nanomaterials are excellent candidates due to the tunable plasmon absorption over a wide range of spectra allowing efficient utilization of solar energy, abundant hot carriers that may overcome the interfacial energy barriers, and low-cost. The localized surface plasmonic resonance (LSPR) effects can also promote charge separation and interfacial transfer. Here, we report metal oxides with tunable oxygen concentration and copper chalcogenides with tunable copper deficiency for photocatalytic nitrogen reduction in ultrapure water. Efficient ammonia production has been achieved under near-infrared (NIR) light illumination. We have demonstrated that for plasmonic semiconducting photocatalysts, the performance is not only dictated by the defects, their negative effects in trapping carriers are also important. Figure 1