Architecting Nitrogen Functionalities on Graphene Oxide Photocatalysts for Boosting Hydrogen Production in Water Decomposition Process. Issue 22 (22nd August 2016)

• Record Type: Journal Article
• Authors: Chen, Liang‐Che; Teng, Chiao‐Yi; Lin, Chun‐Yu; Chang, Hsin‐Yu; Chen, Shean‐Jen; Teng, Hsisheng
• Is Part Of: Advanced energy materials. Volume 6:Issue 22(2016)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-08-22
• Subjects: graphene oxide -- hydrogen production -- nitrogen functionality -- photocatalysis -- water splitting; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201600719
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract : This study elucidates how nitrogen functionalities influence the transition and transfer of photogenerated electrons in graphene‐based materials. Graphene oxide dots (GODs) and Nitrogen‐doped GODs (NGODs) are synthesized by thermally treating graphene oxide (GO) sheets in argon and ammonia, respectively, and then ultrasonically exfoliating the sheets in nitric acid. The nitrogen functionalities of NGODs are mainly quaternary/pyridinic/pyrrolic, and the nitrogen atoms in these functionalities are planar to the GO sheets and repair the vacancy defects on the sheets. Hydrothermal treatment of NGODs in ammonia yields ammonia‐treated NGODs (A‐NGODs), with some pyridinic/pyrrolic groups being converted to amino/amide groups. The nitrogen atoms in the amino/amide groups are not planar to the GO sheets and are prone to donate their lone pair electrons to resonantly conjugate with the aromatic π electrons. The promoted conjugation facilitates the relaxation of photogenerated electrons to the triplet states and prolongs the electron lifetime. When deposited with Pt as the co‐catalyst, the samples catalyze H2 production from an aqueous triethanolamine solution under 420 nm monochromatic irradiation at quantum yields of 7.3% (GODs), 9.7% (NGODs), and 21% (A‐NGODs). The high activity of A‐NGODs demonstrates that architecting nitrogen functionalities effectively mediate charge motion in carbon‐based materials for application to photoenergy conversion. Abstract : The nonplanar configuration of the nitrogen atoms in the amino/amide groups of ammonia‐treated nitrogen‐doped graphene oxide dots (A‐NGODs) promotes the conjugation of the nitrogen lone‐pair electrons with the aromatic π system, facilitating the singlet−triplet intersystem crossing transition of electrons. The photocatalytic H2 production from an aqueous solution suspending A‐NGODs reaches a quantum yield of 21% under 420 nm illumination.