Search

Described herein is a facile one-pot strategy to synthesize N-doped graphitic carbon-incorporated g-C 3 N 4 by adding slight amount of citric acid into urea as the precursor during thermal polymerization. The obtained materials retained the original framework of g-C 3 N 4 and show remarkably enhanced visible light harvesting and promoted photo-excited charge carrier separation and transfer. The high-resolution N 1s spectrum of XPS showed a graphitic N peak, which could be attributed to N-doped graphitic carbon. In addition to the common-recognized light harvesting enhancement and charge carrier recombination inhibition, the incorporation of N-doped graphitic carbon into the planar framework of g-C 3 N 4 is suggested to result in extended and delocalized π-conjugated system of this copolymer, thus greatly elevating the photocatalytic performance for H 2 evolution by water splitting under visible light. The H 2 evolution rate on N-doped graphitic carbon-incorporated g-C 3 N 4 reached 64 μmol h −1 , which is almost 4.3 times the rate on pure g-C 3 N 4 . This approach may provide a promising route for rational design of high performance, cost-effective and metal-free photocatalysts. [ABSTRACT FROM AUTHOR]

• Fe-leaching induces surface reconstruction of Ni-Fe alloy/NC during OER. • Fe-leaching during OER benefits the exposure of more active sites. • The high valent Ni, pyridinic N and metal-N species are the exact active centers. • The fully activated catalyst exhibits excellent OER activity. Understanding the dynamic transformation process of the oxygen evolution reaction (OER) catalysts is of importance for their rational design. Here we first report that Fe-leaching could induce the electrochemical activation of strongly coupled Ni-Fe alloy on N-doped carbon composites to boost the OER performance. It is demonstrated that the leaching of unstable FeOOH mixed layer from the surface of FeNi 3 alloy is responsible for the surface reconstruction and exposure of more active sites. Furthermore, the N-doped carbon, FeNi 3 alloy, together with the accompanying generation of Fe-doped Ni(OH) 2 , synergistically promote the OER activity after fully activation. It is also verified that the high valent Ni species, pyridinic N and the metal-N species are the exact active centers and the fully activated catalyst Fe 0.2 Ni 0.8 /NC-600-a is among the best non-noble OER catalysts to date, which exhibits superior OER performance with a low overpotential (η 20 = 290 mV) and small Tafel slope (76 mV dec−1). This study is helpful to understand the fundamentals of the Ni-Fe alloy catalysts and provides guidance to design advanced catalysts for water oxidation through in-situ electrochemical activation. [ABSTRACT FROM AUTHOR]

The photocatalytic activity enhancement of graphitic carbon nitride (g-C 3 N 4 ) in water splitting were commonly achieved by introducing various functional groups onto/into its planar structure. Herein, oxidized g-C 3 N 4 (CNO) was prepared via an extremely facile K 2 CO 3 activation approach. The high-resolution XPS spectra and solid-state 13 C NMR spectra confirmed the successful introduction of O-containing groups and O atoms were inherited the original molecular framework of g-C 3 N 4 , but exhibited effectively enlarged bonded with C atoms rather than N atoms in the tri-s-triazine structure of g-C 3 N 4 . CNO inherited the original molecular framework of g-C 3 N 4 , but exhibited effectively enlarged surface area and enhanced visible light absorption, and more attrractively, the band structure of g-C 3 N 4 could be well-tuned with the introduction of oxygen species. Importantly, the surface O-containing moieties could strongly interact with cocatalyst Pt and thus remarkably promote interfacial electron transfer and consequent photo-generated charge carrier separation. Consequently, the as-obtained CNO exhibited the remarkably enhanced photocatalytic performance with a H 2 evolution rate of 199.7 μmol h −1 , which is 9 times that of g-C 3 N 4 (22.2 μmol h −1 ). [ABSTRACT FROM AUTHOR]

The modification of graphitic carbon nitride (g-C 3 N 4 ) for visible-light photocatalytic water splitting is a very hot topic due to the more and more serious energy and environment problems. Here we report a novel, general and cost-effective approach via Schiff base chemistry to construct aromatics-grafted g-C 3 N 4 -based copolymers. Based on this general strategy, almost all kinds of aromatics can be grafted into carbon nitride networks. As-synthesized copolymers all show remarkably enhanced and stable visible-light photocatalytic hydrogen evolution performance. In addition, the low cost and small optimized adding amounts of these co-monomers adopted here make the present strategy probably the one of most cost-effective copolymerization approach to construct g-C 3 N 4 -based copolymer photocatalysts. [ABSTRACT FROM AUTHOR]