Chemisorption‐Induced and Plasmon‐Promoted Photofixation of Nitrogen on Gold‐Loaded Carbon Nitride Nanosheets

Abstract

Photocatalytic fixation of nitrogen is a promising method for green conversion of solar light, but has been substantially limited by inefficient activation of the nonpolar N≡N bond and the poor utilization of visible light. In this study, carbon nitride nanosheet composites with abundant nitrogen vacancies and strong plasmonic resonance absorption of visible light have been fabricated through the combination of hydrogen treatment and loading of Au nanoparticles. Ammonia yields of 184 μmol g−1 and 93 μmol g−1 are obtained without any sacrificial agent under full‐light and visible‐light irradiation, respectively. In particular, the visible‐light activity is enhanced tenfold with the help of Au. Combining the experimental results and theoretical calculations, both the hydrogen treatment and Au loading help form nitrogen vacancies on the carbon nitride nanosheets, which promote N2 activation by enhancing the chemisorption. Furthermore, the Au loading further improves the nitrogen reduction efficiency through charging the excited hot electrons formed from the surface plasmonic resonance to the adsorbed N2 molecules.

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

“…H2 atmosphere is able to reduce Bi5O7I, Bi2MoO6, and TiO2, creating large amounts of exposed OVs [147][148][149]. NVs were also reported through H2 treatment [52,150,151]. NH3 is also employed as a reducing gas to treat g-C3N4 and generate CVs [152,153].…”

Photocatalytic Nitrogen Reduction: Challenging Materials with Reaction Engineering

“…Wu et al. combined activation by nitrogen vacancies and plasmonic resonance absorption of Au nanoparticles on carbon nitride nanosheets for nitrogen conversion in pure water [83] …”

Photocatalytic Plasmon‐Enhanced Nitrogen Reduction to Ammonia

“…Wu et al fabricated Au‐loaded graphitic carbon nitride (g‐C 3 N 4 ) nanosheets with abundant NVs. [ 58 ] The high concentration of NVs was obtained by calcining nanosheets under H 2 atmosphere. DFT calculations showed that incorporation of Au reduces the NV generation energy from 3.03 to 0.14 eV which further increases the chances of NV formation.…”

“…Most of the studies utilized a semiconductor (TiO 2 , CeO 2 , Si, Nb-SrTiO 3 , Ag 2 O, (BiO) 2 CO 3 ) in contact with a plasmonic nanomaterial (Au, Ag, Al) to drive photocatalytic NRR. [47,48,[50][51][52][58][59][60][61][62] Incorporation of plasmonic nanostructures allowed to harvest visible light when a wide-gap semiconductor was used. The dominant plasmonenhancement mechanism in metal-semiconductor hybrid system was hot electron injection from the plasmonic metal into the conduction band of the semiconductor.…”

“…[63][64][65] In these types of systems, the plasmonic material acts as the light absorber and enhances NRR activity via hot electron transfer to the cocatalyst and/or field-enhancement. Along with plasmon-enhancement, other strategies such as carrier trapping in surface OV or NV defect states, [47,50,57,58] incorporation of alkali metal cations to increase N 2 adsorption, [51] spatial separation of the oxidation and reduction half reactions [59,60] were used to further improve NRR. The field of N 2 conversion to NH 3 using plasmonic nanostructures is at its infancy and there are many opportunities and challenges to be explored in the future.…”