Photoelectrochemical and photocatalytic studies by applying an organic p-n bilayer for the selective oxidation of ammonia to dinitrogen

Abstract

• Platinum-loaded MWCNT was newly fabricated as a co-catalyst for NH 3 oxidation. • The selective oxidation of NH 3 to N 2 occurred at the cocatalyst-loaded organo-photoanode. • The overall decomposition of NH 3 was photoelectrochemically and photocatalytically accomplished. • Even when Pt was subjected to a high potential, its stable catalysis for the NH 3 oxidation was verified. • By embedding the co-catalyst in a Nafion membrane, the disorder of Pt was avoided at the high applied potential. Ammonia (NH 3 ) is a pollutant that needs to be treated properly. Its oxidative degradation to dinitrogen (N 2 ) involves the transfer of six electrons, and thus, an active catalyst must be applied to accomplish the selective formation of N 2 from NH 3 . In this work, polycrystalline Pt was newly prepared on a multi-walled carbon nanotube (MWCNT) supporter, which was used as a co-catalyst by embedding it in a Nafion® membrane (i.e., Nf[Pt/MWCNT]). The 10 nm-sized Pt particles were well characterized by means of transmission electron microscopy and electrochemistry. We have found that an organic p-n bilayer, comprising fullerene ( n -type) and phthalocyanine (p-type), works as a photoanode capable of oxidation at the phthalocyanine surface. When applying Nf[Pt/MWCNT] as the co-catalyst at the organo-bilayer, the selective NH 3 oxidation was confirmed to occur stably in terms of photoelectrochemistry and photocatalysis, particularly under visible light irradiation.