Graphene and Carbon Dots for Photoanodes with Enhanced Performance

Abstract

The way graphene (GDs) and carbon dots (CDs) are synthesized and combined with TiO2 determine their photoelectrochemical efficiency upon UV and visible LED lights. GDs and CDs are obtained by relatively unexplored top-down methods and conventional bottom-up methods, respectively. Top-down methods consist in the seedless growth of ZnO nanoparticles on the surface of graphene and the electrochemical cleavage of graphene grown on Ni foam. These carbon nanoparticles are later combined with TiO2 by different approaches such as solution mixing, adsorption via APTES linkers, and drop-casting on an already formed TiO2 film. Once the films are formed, they are placed into a photoelectrochemical Zahner cell and irradiated with LED lights at 450 and 360 nm. It is determined that CDs and GDs perform as efficient photosensitizers as demonstrated by an increase of ∼19- and 20-fold net photocurrent density when irradiated with UV and visible LED lights, respectively. We encountered that CDs are more sensitive upon visible light, whereas GDs promptly respond to UV light due to their difference in size-dependent band gap. Importantly, GDs obtained from seedless growth of ZnO are sensitive to both: UV and Vis LED irradiation. The combination of both nanocarbons would expand the absorption range and may be potentially used as cosensitizers toward the construction of more effective and advanced photoanodes.

Think Outside the Lab: Modeling Graphene Quantum Dots in Pandemic Times

“…CVD graphene can grow into monolayers or multilayers depending mainly on the catalytic substrate and other synthesis parameters such as the precursor used, annealing time, cooling ramps, temperature, etc . They are taught about the carbon absorption and diffusion processes that occur on different metal substrates, including Ni and Cu films which, in some cases, may lead graphene to grow into different stacking configurations known as AB (Bernal stacking) and rotated. − Once graphene has grown on the catalytic surface, the sample is then immersed in a basic solution and subjected to an electrochemical cleavage that leads to the exfoliation of small pieces of graphene . Accordingly, the final product of the synthesis can be composed of small graphene fragments of different size, geometry, stacking configuration (AB or rotated), and chemical functionalization.…”

“…18−20 Once graphene has grown on the catalytic surface, the sample is then immersed in a basic solution and subjected to an electrochemical cleavage that leads to the exfoliation of small pieces of graphene. 21 Accordingly, the final product of the synthesis can be composed of small graphene fragments of different size, geometry, stacking configuration (AB or rotated), and chemical functionalization.…”

Milk-Derived Carbon Quantum Dots: Study of Biological and Chemical Properties Provides Evidence of Toxicity

“…At the end, the surface of single carbon quantum dots was determined, the diameter was calculated, and the histograms were plotted. Raw dataset fails as well as after post-processing are available at the date depository [40].…”

Natural Carbon Nanodots: Toxicity Assessment and Theranostic Biological Application

“…CDs synthesis methods can be mainly divided into two categories: One uses physical or chemical means to crack larger carbon structures (e.g., carbon nanotubes, graphite rods, graphene, carbon powder) into tiny CDs; these top-down methods include arc discharge methods, laser ablation methods, chemical oxidation methods, and so on. Small organic molecule precursors, such as sugar, citric acid, and amino acids, are used as carbon sources for these methods through functional group coupling to achieve polymerization to prepare the CDs [15][16][17]. The second category comprises bottom-up methods, such as electrochemical, hydrothermal, pyrolysis, microwave-assisted, and ultrasonic methods [18].…”