Direct Conversion of CO2 to Multi-Layer Graphene using Cu-Pd Alloys

Fast synthesis of large-area bilayer graphene film on Cu

Bilayer graphene (BLG) is intriguing for its unique properties and potential applications in electronics, photonics, and mechanics. However, the chemical vapor deposition synthesis of large-area high-quality bilayer graphene on Cu is suffering from a low growth rate and limited bilayer coverage. Herein, we demonstrate the fast synthesis of meter-sized bilayer graphene film on commercial polycrystalline Cu foils by introducing trace CO₂ during high-temperature growth. Continuous bilayer graphene with a high ratio of AB-stacking structure can be obtained within 20 min, which exhibits enhanced mechanical strength, uniform transmittance, and low sheet resistance in large area. Moreover, 96 and 100% AB-stacking structures were achieved in bilayer graphene grown on single-crystal Cu(111) foil and ultraflat single-crystal Cu(111)/sapphire substrates, respectively. The AB-stacking bilayer graphene exhibits tunable bandgap and performs well in photodetection. This work provides important insights into the growth mechanism and the mass production of large-area high-quality BLG on Cu.

Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment

In this work, we report the conversion of carbon dioxide (CO₂) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H₂) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H₂ plasma pre-treatment powers (100-400 W). The number of layers is reduced with increasing H₂ plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H₂ plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H₂ plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted.

Temperature-dependent CO2 sorption and thermal-reduction without reactant gases on BaTiO3 nanocatalysts at low temperatures in the range of 300-1000 K

Carbon utilization techniques to mitigate the impact on global warming are an important field in environmental science. CO₂ reduction is a significant step for carbon utilization. However, CO₂ reduction with less energy consumption has major challenges. In this study, CO₂ thermal reduction was demonstrated using nanocatalysts at temperatures lower than 1000 K, and the CO₂ sorption and reduction mechanisms within the temperature range of 300-1000 K were evaluated. The physical adsorption on nanocatalysts with a crystal size of 7.4 ± 0.4 nm (10 nm-nanocatalysts) majorly occurred at 300 K and was considerably decreased beyond that temperature. CO₂ chemisorption occurred above 450 K and subsequent CO₂ reduction occurred above 500 K, which was expected based on the temperature-programmed reaction. CO₂ reduction decreased above 900 K by the deactivation of the 10-nm nanocatalyst as a result of its crystal growth. The transmission electron microscopy images also indicated the complete reduction of CO₂ into carbon products at 600 and 800 K. Therefore, an optimal condition of CO₂ reduction in the temperature range of 500-800 K. The highly active thermocatalyst achieved CO₂ reduction into CO and carbon products without any reducing agents even at an extremely low temperature (500 K). In summary, temperature-dependent CO₂ sorption and reduction were observed on the 10-nm nanocatalyst; CO₂ physical adsorption at 300-500 K, CO₂ chemisorption above 450 K, CO₂ reduction at 500-850 K, and CO₂ and CO releases above 800 K.

Bio-inspired graphene-based nano-systems for biomedical applications

The increasing demands of environmentally sustainable, affordable, and scalable materials have inspired researchers to explore greener nanosystems of unique properties which can enhance the performance of existing systems. Such nanosystems, extracted from nature, are state-of-art high-performance nanostructures due to intrinsic hierarchical micro/nanoscale architecture and generous interfacial interactions in natural resources. Among several, bio-inspired nanosystems graphene nanosystems have emerged as an essential nano-platform wherein a highly electroactive, scalable, functional, flexible, and adaptable to a living being is a key factor. Preliminary investigation project bio-inspired graphene nanosystems as a multi-functional nano-platform suitable for electronic devices, energy storage, sensors, and medical sciences application. However, a broad understanding of bio-inspired graphene nanosystems and their projection towards applied application is not well-explored yet. Considering this as a motivation, this mini-review highlights the following; the emergence of bio-inspired graphene nanosystems, over time development to make them more efficient, state-of-art technology, and potential applications, mainly biomedical including biosensors, drug delivery, imaging, and biomedical systems. The outcomes of this review will certainly serve as a guideline to motivate scholars to design and develop novel bio-inspired graphene nanosystems to develop greener, affordable, and scalable next-generation biomedical systems.

Direct electrosynthesis of 52% concentrated CO on silver's twin boundary

The gaseous product concentration in direct electrochemical CO₂ reduction is usually hurdled by the electrode's Faradaic efficiency, current density, and inevitable mixing with the unreacted CO₂. A concentrated gaseous product with high purity will greatly lower the barrier for large-scale CO₂ fixation and follow-up industrial usage. Here, we developed a pneumatic trough setup to collect the CO₂ reduction product from a precisely engineered nanotwinned electrocatalyst, without using ion-exchange membrane. The silver catalyst's twin boundary density can be tuned from 0.3 to 1.5 × 10⁴ cm^-1. With the lengthy and winding twin boundaries, this catalyst exhibits a Faradaic efficiency up to 92% at -1.0 V and a turnover frequency of 127 s^-1 in converting CO₂ to CO. Through a tandem electrochemical-CVD system, we successfully produced CO with a volume percentage of up to 52%, and further transformed it into single layer graphene film.