EES catalysis最新文献

Minimizing the power-specific iridium loading in polymer electrolyte water electrolysis (PEWE) is essential for the commercialization and upscaling of this technology. However, decreasing the iridium loading can severely affect performance and stability. Microporous layers (MPL) can overcome some of these issues by maximizing catalyst utilization and increasing cell efficiency. In this study, we combined advanced synchrotron and lab-based X-ray imaging techniques and electrochemical characterization to improve the PEWE cell performance at low Ir loadings using novel MPLs. For the first time, the 3D nanostructure of the catalyst layer was characterized under dry and wet conditions using ptychographic X-ray laminography. We prepared catalyst layers (CL) at three iridium loadings between 2.5 and 0.1 mg_Ircm⁻² in two different configurations: depositing either on the membrane or on the Ti-substrate (MPL). The MPL structure and catalyst distribution at its surface were analyzed using X-ray tomographic microscopy. Moreover, we investigated the effect of introducing a thin protective Pt coating on the MPL. The electrochemical performance was characterized for all cell combinations, and an in-depth kinetic analysis revealed information on CL utilization. The MPLs exhibit significant benefits for reducing iridium loadings, allowing performance to be sustained with only modest voltage losses. The challenges in fabricating anodic CLs with reduced catalyst loadings and the advantages of using an MPL in both configurations are discussed. The findings of this study contribute to accomplishing the required targets in terms of power-specific iridium loadings for future PEWE systems.

One-dimensional (1D) nanostructured inorganic semiconductors have been extensively investigated for efficiently promoting their photocatalytic performances, but it still remains unclear for metal–organic framework (MOF)-based photocatalysis. Herein we present the synthesis 1D Mn-TBAPy MOF nanotubes (denoted as Mn-TBAPy-NT) and give the first demonstration of the marked ability of the 1D nanotube structure to promote charge separation of MOFs relative to that in the Mn-TBAPy single crystal (denoted as Mn-TBAPy-SC), a feature proposed to result from the effect of strain on the nanotubes. As specifically determined using transient absorption (TA) spectroscopy, Mn-TBAPy-NT exhibits a long-lived internal charge-separated (ICS) state (255.6 ns), longer than that for Mn-TBAPy-SC (4.6 ns) and a feature apparently responsible for its over 30-fold promoted hydrogen evolution with a rate of 203.5 μmol h⁻¹ (ca. 10.2 mmol h⁻¹ g_cat⁻¹) under visible light and a benchmark apparent quantum efficiency (AQE), of 11.7% at 420 ± 10 nm, among MOF-type photocatalysts. Our results open a new avenue for developing highly efficient MOF-based photocatalysts.

Bioinspired nickel phosphide electrocatalysts can produce more complex multi-carbon products than natural photosynthetic enzymes but controlling C-product selectivity and suppressing H₂ evolution remain open challenges. Here, we report a significant shift in the CO₂RR product distribution on Ni₂P in the presence of boric acid/borate, a soluble Lewis acid/base co-catalyst. Using Ni₂P without a co-catalyst, CO₂ reduction produces a mixture of methyl glyoxal (C₃) > 2,3-furnadiol (C₄) and formic acid (C₁) with 100% Faradaic efficiency for carbon products. Addition of boric acid/borate shifts product selectivity to ethylene glycol (EG) with an 85% CO₂-Faradaic efficiency (at 10 mM, 0 V vs. RHE), with the balance being the aforementioned C₁, C₃ and C₄ products. The mechanism of EG formation is proposed to occur by the co-catalyst activating a reaction between surface *hydride and *glycolaldehyde on Ni₂P, while suppressing the aldol C–C coupling reaction that forms the C₃ and C₄ products. The formation of an intermediate borate-EG-diester, [(OCH₂CHO)₂B]⁻, is detected by ¹¹B-NMR, which hydrolyzes to release the EG product. Extended electrolysis of boric acid modifies the surface of Ni₂P by forming *BO₃–Ni₂P, as shown by XPS. CO₂ electro-reduction on *BO₃–Ni₂P in the absence of free boric acid produces exclusively ethylene oxide (EO), which slowly hydrolyzes to EG in the bicarbonate electrolyte. The combined Faradaic efficiencies for CO₂RR products EO + EG with free boric acid as the co-catalyst and *BO₃–Ni₂P as the cathode reaches 88% (at 0 V vs. RHE), a record carbon selectivity. This work illustrates the feasibility of using Lewis acid/base co-catalysts to change the established chemical reaction mechanism of an electrocatalyst to form a new, chemically predictable, more valuable product in high yield.

The Pt–Mn₂O₃/CN catalyst formed through synthesis via a solvent-thermal method involves a synergistic combination of polymer CN and Pt nanoparticles loaded on Mn₂O₃ to catalyze the degradation of toluene. The composition incorporates Mn₂O₃ as the central element for photothermal conversion, CN as a uniformly dispersed matrix for Pt nanoparticles, and Pt as the catalytically active center, demonstrating significant efficacy. Particularly noteworthy is the discernible enhancement in the photothermal catalytic degradation capability of the Pt–Mn₂O₃/CN composite catalyst, specifically in the context of toluene. When subjected to light intensity of 300 mW cm⁻² and a toluene concentration of 400 ppm, Pt–Mn₂O₃/CN achieves toluene conversion and CO₂ mineralization rates of 99% and 80.9%, respectively. This improvement primarily stems from the Pt nanoparticles inducing a substantial presence of oxygen vacancies within the catalyst structure, thereby increasing the oxygen adsorption capacity and surface mobility. This, in turn, activates adsorbed oxygen species at the catalyst's interface. The adept utilization and conversion of solar irradiance for volatile organic compound (VOC) abatement underscore its potential as an environmentally friendly and renewable energy source.

Direct electrochemical CO₂ conversion in carbonate/bicarbonate based CO₂ capture media has emerged as a promising technology for integrating carbon capture and CO₂ electroreduction processes in recent years, garnering significant attention from researchers owing to its high energy efficiency and carbon efficiency. For a holistic understanding of the development status of this field, this minireview summarizes a series of studies on the mechanism of carbonate/bicarbonate electrolyzers. Detailed mechanisms of the electrochemical conversion of carbonate/bicarbonate, the evolution of electrolyzers, and factors influencing the performance of electrolyzers are introduced. A summary of carbonate/bicarbonate electrolyzers' performance is also provided. Representative systems and materials for regulating the selectivity towards various products (e.g., CO, formate, methane, ethylene, and ethanol) and the cell voltage are highlighted. Furthermore, the challenges and future opportunities in this research area are also discussed.

Photoelectrodes with FTO/Au/Sb₂Se₃/TiO₂/Au architecture were studied in photoelectrochemical CO₂ reduction reaction (PEC CO₂RR). The preparation is based on a simple spin coating technique, where nanorod-like structures were obtained for Sb₂Se₃, as confirmed by SEM images. A thin conformal layer of TiO₂ was coated on the Sb₂Se₃ nanorods via ALD, which acted as both an electron transfer layer and a protective coating. Au nanoparticles were deposited as co-catalysts via photo-assisted electrodeposition at different applied potentials to control their growth and morphology. The use of such architectures has not been explored in CO₂RR yet. The photoelectrochemical performance for CO₂RR was investigated with different Au catalyst loadings. A photocurrent density of ∼7.5 mA cm⁻² at −0.57 V vs. RHE for syngas generation was achieved, with an average Faradaic efficiency of 25 ± 6% for CO and 63 ± 12% for H₂. The presented results point toward the use of Sb₂Se₃-based photoelectrodes in solar CO₂ conversion applications.

Converting carbohydrate-rich biomass waste directly to γ-valerolactone (GVL) is highly attractive but challenging owing to the inert nature and high complexity of biomass, necessitating a versatile and selective catalytic system. Herein, we describe the first direct conversion of monosaccharides (glucose, fructose, and xylose) and polysaccharides (cellulose and hemicellulose) in high yields under mild conditions. We also present the first direct conversion of raw lignocellulose, starch, and chitin biomass to GVL. Using the homogeneous catalyst Ru-MACHO-BH in H₃PO₄(aq) under 30 bar H₂ at 125–140 °C for 24–120 hours provides GVL in excellent yields (26–48 mol%).

The archetype surface frustrated Lewis pair (SFLP) that facilitates CO₂ photocatalytic hydrogenation to methanol and carbon monoxide, is an InOH⋯In site positioned in the surface of a nanoscale indium oxide hydroxide, denoted In₂O_3−x(OH)_y. Proximal Lewis acid In(III) and Lewis base InOH of this genre serve as surface active sites that enable the photochemical heterolytic H₂ dissociation and reduction of CO₂ to the mentioned products. The conversion rate enabled by light has been found to far exceed that enabled by heat. Efforts to enhance the CO₂ photocatalytic performance of the SFLP have involved modifications of the Lewis acidity and basicity through isomorphic substitution of In(III) with Bi(III) and changes in the population of oxygen vacancies through control of oxide non-stoichiometry. Replacement of the Lewis base hydroxide InOH by the stronger Lewis base amine InNH₂ heretofore remains unexplored. The strategy described herein to explore this opportunity begins with the synthesis of In₂O_3−x(EDA)_y. This new material is proven to contain an InNH₂⋯In SFLP and its CO₂ photocatalytic performance is demonstrated to outperform that of its In₂O_3−x(OH)_y progenitor. Tailored Lewis acidity and basicity surfaces bring CO₂ photocatalysis another step closer to the vision of solar CO₂ refineries.

CO₂ emission has inarguably become one of the greatest challenges ever faced by mankind since industrial revolution. Techniques aiming at capture, storage and utilization of CO₂ have attracted tremendous interest from both industry and academia. Thermal, electrical and photo-catalytic conversion of CO₂ to value-added chemicals and fuels is the most well-known approach for CO₂ utilization. In particular, photocatalytic reduction of CO₂ (CO₂PR) directly employs solar energy as the driving force to activate CO₂, yielding various products including CO, CH₄ and C₂₊ hydrocarbons. CO₂PR, which mimics photosynthesis occurring in nature, is also regarded as “artificial photosynthesis” and is believed to be a promising approach toward carbon neutral economy. Recently, metal halide perovskites (MHPs) have emerged as potential photocatalysts for CO₂PR, owing to their flexible structures and excellent photoelectronic properties. This review presents a comprehensive overview of state-of-the-art developments in MHP-based catalysts for CO₂PR. Firstly, the crystal structures and photoelectric properties of MHPs are reviewed in detail, as they are the key factors determining CO₂PR catalytic performance. Secondly, design strategies to promote the catalytic efficiency of CO₂PR to CO conversion for both lead-based and lead-free MHPs are discussed, including morphological modifications, co-catalyst modifications, ion doping and crystal plane modifications. Thirdly, this review addresses MHP-based CO₂PR to CH₄ and C₂₊ products, with special emphasis on approaches adopted to promote specific product selectivity. Lastly, our perspectives and opinions are given on current research challenges and future directions for CO₂PR, which we consider are critical for its industrialization.

Photocatalysis is considered as an effective approach to address energy and environmental issues. Carbon nitride (CN) is a promising metal-free semiconductor photocatalyst because of its unique properties such as tunable electronic band structure, facile/cheap synthesis and high chemical stability. However, the pristine CN prepared by the traditional thermal polymerization method is usually an amorphous or semi-crystalline conjugated bulk with a high density of structural defects, resulting in its moderate photocatalytic activity. Increasing the crystallinity of CN is an effective strategy to enhance its photocatalytic activity, and a few methods have been proposed, including high-temperature and high-pressure treatment, ionothermal method, solvothermal synthesis and microwave-assisted thermal polymerization. This review summarizes recent advances in the preparation of crystalline carbon nitrides (CCNs) and the design of CCNs-based photocatalysts in terms of nanostructure design, molecular structure engineering and construction of CCNs-based heterojunctions. In addition, their applications in a range of photocatalysis fields such as water splitting, carbon dioxide reduction, degradation of pollutants, organic synthesis and H₂O₂ production are reviewed. Finally, the concluding remarks are presented as well as challenges and prospects for future development of CCNs-based photocatalysts.