Photoelectrochemical Synthesis of Ammonia on the Aerophilic-Hydrophilic Heterostructure with 37.8% Efficiency

Photoelectrochemical nitrogen reduction reaction can provide a useful source of ammonia and transportable carrier of hydrogen, but the process is limited by the photocathodes with poor conversion efficiency and low production rate. Here, we have designed a unique aerophilic-hydrophilic heterostructured Si-based photocathode for nitrogen-to-ammonia fixation in an acid electrolyte under mild conditions, achieving a high ammonia yield rate of ∼18.9 μg⋅cm−2⋅hr−1 and an excellent faradic efficiency of 37.8% at −0.2 V versus a reversible hydrogen electrode. The heterostructure based on the Au nanoparticles highly dispersed in poly(tetrafluoroethylene) porous framework enriches nitrogen molecular concentration at the Au active sites while manipulateing the proton activity with suppressed hydrogen evolution reactions. DFT calculation indicates that such heterostructure reduces the energy barrier for the nitrogen reduction reaction. The aerophilic-hydrophilic heterostructure provides a new insight on designing efficient and robust photocathodes for nitrogen fixation.