Publications by authors named "Juan Carlos Colmenares"

Article Synopsis
  • Clean hydrogen production through electrocatalysis and photocatalysis is seen as a key solution to the energy crisis, but finding effective catalysts remains a challenge.
  • The review highlights advanced nanoscale electrocatalysts and photocatalysts designed for various reaction settings, like acidic and alkaline electrolytes and seawater, and discusses modification techniques to enhance performance.
  • It also explores the properties and mechanisms of these catalysts in improving hydrogen production, concluding with insights into future advancements in this field.
View Article and Find Full Text PDF

The loading of graphitic carbon nitride (gCN) with transition metals has received significant attention for efficient light-driven catalysis. However, the contribution of the loaded metals to enhanced performance remains unclear. In this study, Cu is loaded onto gCN to understand how photocatalytic activity is regulated by the loaded metals.

View Article and Find Full Text PDF

Catalytic conversion of lignin to value-added aromatic compounds is still an open challenge, since the selective cleavage of the linkages interconnecting the aromatic molecules, especially the β-O-4 ones, is not efficiently achieved yet. Herein, novel titania-based nanostructured materials were synthesized using low-power-low-frequency ultrasound that demonstrated high efficiency for the selective cleavage of C-C bond of β-O-4 linkages of lignin-inspired model compounds. Going a step ahead, experiments of sonophotocatalytic valorization of 2-phenoxy-1-phenylethanol were contacted for the first time, where the exposure to ultrasound leading to better conversion and selectivity towards the desired products in the case of the novel ultrasound-synthesized nano-photocatalyst.

View Article and Find Full Text PDF

Over the past few decades, organic-inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air-water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial.

View Article and Find Full Text PDF

The research for "green" and economically feasible approaches such as (photo)catalysis especially for biomass valorization such as selective oxidation of biomass derived compounds like aromatic alcohols to corresponding aldehyde by avoiding the harsh reaction conditions and the addition of reagents concentrate the focus of attention the last years. Hence, design and development of novel photocatalyst for the partial selective oxidation is highly desirable. In this research work, ultrasonication of different frequencies (22, 40, 80 kHz) and different amplitudes was utilized as synthesis tool in order to obtain novel materials by precipitation method.

View Article and Find Full Text PDF

The challenge of improving the activity of TiO by modifying it with metals and using it for targeted applications in microreactor environments is an active area of research. Recently, microreactors have emerged as successful candidates for many photocatalytic reactions, especially for the selective oxidation process. The current work introduces ultrasound-assisted catalyst deposition on the inner walls of a perfluoro-alkoxy alkane (PFA) microtube under mild conditions.

View Article and Find Full Text PDF

An environmentally friendly mixed-halide perovskite MA Bi Cl I with a bandgap funnel structure has been developed. However, the dynamic interfacial interactions of bandgap funneling in MA Bi Cl I perovskites in the photoelectrochemical (PEC) system remain ambiguous. In light of this, single- and mixed-halide lead-free bismuth-based hybrid perovskites-MA Bi Cl I and MA Bi I (named MBCl-I and MBI)-in the presence and absence of the bandgap funnel structure, respectively, are prepared.

View Article and Find Full Text PDF

The photocatalytic system using hydrohalic acid (HX) for hydrogen production is a promising strategy to generate clean and renewable fuels as well as value-added chemicals (such as X /X ). However, it is still challenging to develop a visible-light active and strong-acid resistive photocatalyst. Hybrid perovskites have been recognized as a potential photocatalyst for photovoltaic HX splitting.

View Article and Find Full Text PDF

The continuous increase of the demand in merchandise and fuels augments the need of modern approaches for the mass-production of renewable chemicals derived from abundant feedstocks, like biomass, as well as for the water and soil remediation pollution resulting from the anthropogenic discharge of organic compounds. Towards these directions and within the concept of circular (bio)economy, the development of efficient and sustainable catalytic processes is of paramount importance. Within this context, the design of novel catalysts play a key role, with carbon-based nanocatalysts (CnCs) representing one of the most promising class of materials.

View Article and Find Full Text PDF

Developing functional materials from biomass is a significant research subject due to its unique structure, abundant availability, biodegradability and low cost. A series of chitosan-lignin (CL) composites were prepared through a hydrothermal method by varying the weight ratio of chitosan and lignin. Subsequently, these CL composites were combined with titania (T) to form a nanocomposite (T/CL) using sol-gel and hydrothermal based methods.

View Article and Find Full Text PDF

Highly oriented, layered, and mechanically resilient films of polydopamine (PDA) have been synthesized from the air/water interface. The films show a unique layered structure, as shown by scanning and transmission electron studies (SEM/TEM) and X-ray diffraction analysis (XRD), which resemble that of 2D layered materials. The films exhibit a composition typical of PDA-based materials, as evidenced by X-ray photoelectron spectroscopy (XPS); moreover, the samples present the distinctive resonance modes of PDA-based nanomaterials in Raman and infrared spectroscopy (FTIR) experiments.

View Article and Find Full Text PDF

The removal of uranium species from aqueous phases using non-hazardous chemicals is still an open challenge, and remediation by adsorption is a prosperous strategy. Among the most crucial concerns regarding the design of an efficient material as adsorbent are, except the cost and the green character, the feasibility to be stable and effective under acidic pH, and to selectively adsorb the desired metal ion (e.g.

View Article and Find Full Text PDF

Solar energy-driven processes for biomass valorization are priority for the growing industrialized society. To address this challenge, efficient visible light-active photocatalyst for the selective oxidation of biomass-derived platform chemical is highly desirable. Herein, selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) was achieved by visible light-driven photocatalysis over titania.

View Article and Find Full Text PDF
Article Synopsis
  • Ultradeep desulfurization of fuels is essential for reducing environmental pollution caused by sulfur compounds released during fuel combustion.
  • Adsorptive desulfurization (ADS) is a promising method due to its low energy requirements and ability to operate at ambient conditions without chemicals.
  • Metal organic frameworks (MOFs) have shown high effectiveness as adsorbents for thiophenic compound removal, and the review discusses their applications, mechanisms, and potential improvements in desulfurization efficiency.
View Article and Find Full Text PDF

A new field where the utilization of mechanochemistry can create new opportunities is materials chemistry, and, more interestingly, the synthesis of novel nanomaterials. Ball-milling procedures and ultrasonic techniques can be regarded as the most important mechanochemical synthetic tools, since they can act as attractive alternatives to the conventional methods. It is also feasible for the utilization of mechanochemical forces to act synergistically with the conventional synthesis (as a pre-treatment step, or simultaneously during the synthesis) in order to improve the synthetic process and/or the material's desired features.

View Article and Find Full Text PDF

Catalysis is an integral part of a majority of chemical operations focused on the generation of value-added chemicals or fuels. Similarly, the extensive use of fossil-derived fuels and chemicals has led to deterioration of the environment. Catalysis currently plays a key role in mitigating such effects.

View Article and Find Full Text PDF

Depleting conventional fuel reserves has prompted the demand for the exploration of renewable resources. Biomass is a widely available renewable resource that can be valorized to produce fuels, chemicals, and materials. Among all the fractions of biomass, lignin has been underutilized.

View Article and Find Full Text PDF

Formation of thin layers of photocatalyst in photo-microreactor is a challenging work considering the properties of both catalyst and the microchannel material. The deposition of semiconductor materials on fluoropolymer based microcapillary requires the use of economical methods which are also less energy dependent. The current work introduces a new method for depositing nanoparticles of TiO on the inner walls of a hexafluoropropylene tetrafluoroethylene microtube under mild conditions using ultrasound technique.

View Article and Find Full Text PDF

Correction for 'Selective photocatalysis of lignin-inspired chemicals by integrating hybrid nanocatalysis in microfluidic reactors' by Juan Carlos Colmenares et al., Chem. Soc.

View Article and Find Full Text PDF

Promising semiconductor-based photocatalysis toward achieving efficient solar-to-chemical energy conversion is an ideal strategy in response to the growing worldwide energy crisis, which however is often practically limited by the insufficient photoinduced charge-carrier separation. Here, a rational cascade engineering of Au nanoparticles (NPs) decorated 2D/2D Bi WO -TiO (B-T) binanosheets to foster the photocatalytic efficiency through the manipulated flow of multichannel-enhanced charge-carrier separation and transfer is reported. Mechanistic characterizations and control experiments, in combination with comparative studies over plasmonic Au/Ag NPs and nonplasmonic Pt NPs decorated 2D/2D B-T composites, together demonstrate the cooperative synergy effect of multiple charge-carrier transfer channels in such binanosheets-based ternary composites, including Z-scheme charge transfer, "electron sink," and surface plasmon resonance effect, which integratively leads to the boosted photocatalytic performance.

View Article and Find Full Text PDF

This tutorial review assesses the available and possible strategies for attaining higher selectivity and yield of value-added chemicals from lignin using nanocatalysts embedded in a photomicroreactor. The design of the photomicroreactor, the choice of photocatalysts and the techniques for assembling the catalysts in such confined spaces are crucial elements. Lignin, a predominant industrial byproduct and pollutant, has been recognized today as a rich reservoir for aromatic chemicals and a prominent resource.

View Article and Find Full Text PDF

In the present review, we would like to draw the reader's attention to the polymer-based hybrid materials used in photocatalytic processes for efficient degradation of organic pollutants in water. These inorganic-organic materials exhibit unique physicochemical properties due to the synergistic effect originating from the combination of individual elements, i.e.

View Article and Find Full Text PDF

Lignocellulosic biomass represents a natural renewable chemical feedstock that can be used to produce high value-added chemicals and platform molecules. Nowadays, there are extensive studies on a variety of aspects concerning the valorization of lignocellulosic biomass into desirable products. Among the current technologies for biomass conversion some require extreme conditions along with high temperatures and pressures.

View Article and Find Full Text PDF