Improving hydrogen production for carbon-nitride-based materials: crystallinity, cyanimide groups and alkali metals in solution working synergistically

Abstract

The recent findings on the fundamental understanding of the activity of carbon nitride-based materials in the hydrogen evolution reaction (HER) allow to design rationally the photocatalytic systems with improved activities....

Synergistically interactive MnFeM (M = Cu, Ti, and Co) sites doped porous g-C3N4 fiber-like nanostructures for an enhanced green hydrogen production

“…27,[33][34][35][36][37][38][39] Unlike other approaches, metal doping possesses many advantages because it allows the uniform distribution of metal atoms inside the skeleton structure of a porous g-C 3 N 4 nanostructure, which makes metal atoms more accessible and stable, as well as maximizes their usage during the HER. [40][41][42][43] For example, the photocatalytic HER rate of Ag (26 wt%)/ g-C 3 N 4 porous nanofibers (625 μmol g −1 h −1 ) was superior to that of pristine g-C 3 N 4 by 6.6 times, due to their optical properties, large surface areas, and better visible light-absorption. 44 The photocatalytic HER rate of g-C 3 N 4 nanosheets doped with Cu (3.5 wt%, 3774.35 μmol g −1 h −1 ) was 3 times higher than that of bare g-C 3 N 4 nanosheets.…”

Carbon Nitride-Based Nanomaterials as a Sustainable Catalyst for Biodiesel Production

“…Synthesis of Na-PHI. The Na-PHI material was synthesized according to the previously method reported by Teixeira et al 25 A mixture of melamine (10 g) and sodium chloride (NaCl�100 g) was ground in a ball mill equipment for 5 min with frequency of 25 rpm•s −1 . The solid mixture was placed in a porcelain crucible and heated up in an oven to 600 °C with a heating rate of 2.3 °C min −1 under constant nitrogen flow (5 L min −1 ), held at 600 °C for 4 h. After cooling, the product was washed with deionized water (1 L) at 90 °C during 2 h, to make easier the solubilization of remaining NaCl.…”

“…Synthesis of LiK-PHI. The LiK-PHI material was synthesized according to the method previously reported by Teixeira et al 25 A mixture of 5-aminotetrazole (0.99 g) and lithium chloride/potassium chloride (LiCl/KCl) eutectics [4.97 g 9:11 wt ratio (2.24 g LiCl/2.73 g KCl)] was placed in a ball mill cup. The solid mixture was ground in a ball mill equipment for 5 min with frequency of 25 rpm s −1 .…”

“…32 All Fourier-transform infrared (FTIR) spectra (Figure 2b) of CNs show the typical pattern characteristic of carbon nitrides, observed in the literature. 25,39 The bands corresponding to the heptazine ring stretching (C−N and C�N) are located in the region between 1650 and 1200 cm −1 . 32 A sharp and strong band corresponding to the characteristic breathing mode of the triazine ring units was observed at 804 cm −1 .…”

“…In this sense, carbon nitride-based nanomaterials (CNs) present an interesting efficient alternative as heterogeneous catalysts for biodiesel production via transesterification reactions. CNs have been widely explored as a catalyst and support for a myriad of applications due to them being composed of earth abundant elements, facile synthesis, nontoxicity, optical properties, and high stability, such as hydrogen production, , CO 2 reduction reaction, , cycloaddition reactions, antibiotics degradation, − transesterification/esterification reactions, ,, among others. CNs can be constituted by three different structures or a mixture of them: (i) polymeric carbon nitride (PCN) formed by a linear polymer consisting of heptazines interconnected via secondary nitrogen; (ii) “poly­(heptazine imide)” (PHI) which are rings of six heptazine units that are linked by NH bridges to form an extended two-dimensional (2D) network; and (iii) poly­(triazine imides) with intercalated LiCl (PTI/Li + Cl – ) interconnected via tertiary amines, without active basicity, due to the lack of localized electrons in the π state. , Among the CN characteristics, the most important is that these materials present a cost-effective synthesis and high stability.…”