Heterogenous Fenton‐like reactions are frequently proposed for treating persistent pollutants through the generation of reactive radicals. Despite great efforts to optimize catalyst activity, their ...broad application in practical settings has been restricted by the low efficiency of hydrogen peroxide or persulfate decomposition as well as ultrafast self‐quenching of the activated radicals. Theoretical calculations predicted that two‐dimensional (2D) metallic 1T phase MoS2 materials with exposed (001) surfaces and (100) edges should have remarkable affinity towards crucial intermediates in the peroxymonosulfate (PMS) activation process. X‐ray photoelectron spectroscopy and in situ Raman spectroscopy were used to show that the exposed metallic Mo sites accelerate the rate‐limiting step of electron transfer. A lamellar membrane made from a stack of 2D MoS2 with tunable interspacing was then designed as the catalyst. The non‐linear transport between the MoS2 nanolayers leads to high water diffusivity so that the short‐lived reactive radicals efficiently oxidize contaminants.
Organic compounds were efficiently degraded by Fenton‐like reactions. Bisphenol A was removed by generating catalytic peroxymonosulfate (PMS) in a MoS2 membrane with a tunable interspacing. The rapid degradation is enabled by the enhanced generation of radicals and their close proximity to the organic compounds in the nanostructure.
The ever‐increasing anthropogenic consumption of fossil fuels and the resulting large emission of CO2 have led to a severe energy crisis and climate change. Photocatalytic reduction of CO2 into fuels ...using solar energy is considered as a promising way to address these two problems. In particular, photoelectrochemical (PEC) reduction of CO2 can integrate and optimize the advantages of both photocatalysis and electrocatalysis for improved conversion efficiency and selectivity. In addition to the charge generation and separation, the efficient reduction of CO2 on the surface of a semiconductor‐based photoelectrode remains a scientifically critical challenge, which can be greatly enhanced by the surface modification of cocatalysts. Herein, the recent developments of cocatalysts in PEC CO2 reduction over semiconductor‐based photoelectrodes are described, and the basic principles of PEC CO2 reduction and the function of the cocatalyst in photoelectrocatalysis are discussed. The structure optimization between the photoelectrodes and the cocatalysts is also summarized since the loading of cocatalyst may shield the incident light and hinder charge transfer between them. Furthermore, the challenges and perspectives for PEC reduction of CO2 are also presented.
The recent developments of cocatalysts in photoelectrochemical reduction of CO2 over semiconductor‐based photoelectrodes are described. The basic principles of PEC CO2 reduction and the function of the cocatalyst in photoelectrocatalysis are discussed. The structure optimization between photoelectrodes and cocatalysts is also summarized since the loading of cocatalyst may shield the incident light and hinder the charge transfer between them.
The layered molybdenum chalcogenide MoS2 has attracted wide attention due to its potential electrochemical applications. Based on its unique physical and chemical properties, numerous advances have ...shown that nanostructured MoS2, with the advantages of low cost and outstanding properties, is a promising candidate for environmentally benign energy conversion and storage (ECS) devices. Nowadays, in order to lessen the reliance on fossil fuels, the production of hydrogen from water splitting has become an important issue. Hence, developing catalysts composed of earth-abundant elements that possess activities comparable to those of noble metals is of great urgency. According to DFT calculations in terms of HER free-energy diagrams, MoS2 could be used as an effective substitute for noble metals. Meanwhile, MoS2 with various structures has also been applied in the field of energy storage, including batteries and supercapacitors. Additionally, due to their layer-dependent electrical properties, MoS2-based electrochemical devices have been applied as sensors for a variety of chemicals. In this review, we summarize recent advances in the development of MoS2 with high-performance in various electrochemical domains, and recent progress in discovering the mechanisms underlying the enhanced activity. Moreover, we summarize the critical obstacles facing MoS2, and discuss strategies for further improving its activity. Lastly, we offer some suggestions on the pathways toward achieving high performance competitive with noble metal counterparts, and perspectives on practical applications of MoS2 in the future.
Application of transition metal phosphide (TMP) catalysts for full water splitting has great potential to help relieve the energy crisis. Various methods have been investigated to obtain high ...catalytic activity, but the use of electronic structure regulation by incorporation of different elements is of particular simplicity and significance for development of a universal TMP synthesis method. We herein describe a novel approach for fabricating a series of TMPs by pyrolyzing phytic acid (PA) cross-linked metal complexes. The introduction of oxygen atoms into TMPs not only enhanced their intrinsic electrical conductivity, facilitating electron transfer, but activated active sites via elongating the M–P bond, favoring the hydrogen evolution reaction (HER) or oxygen evolution reaction (OER). MoP exhibited relative low HER overpotentials of 118 mV and 93 mV while supporting a current density of 20 mA·cm–2 in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively. When CoP was applied as a catalyst for OER, only 280 mV overpotential was required to reach current density of 10 mA·cm–2. Additionally, PA-containing precursors enabled intimate embedding of TMPs onto a flexible substrate surface (carbon cloth), so that electron injection from substrate and transport to the active sites was facilitated. Remarkably, an alkaline electrolyzer was able to achieve a current density of 40 mA·cm–2 at the low voltage of 1.6 V, demonstrating its potential for practical overall water splitting without the use of noble metals.
Copper can efficiently electro‐catalyze carbon dioxide reduction to C2+ products (C2H4, C2H5OH, n‐propanol). However, the correlation between the activity and active sites remains ambiguous, impeding ...further improvements in their performance. The facet effect of copper crystals to promote CO adsorption and C−C coupling and consequently yield a superior selectivity for C2+ products is described. We achieve a high Faradaic efficiency (FE) of 87 % and a large partial current density of 217 mA cm−2 toward C2+ products on Cu(OH)2‐D at only −0.54 V versus the reversible hydrogen electrode in a flow‐cell electrolyzer. With further coupled to a Si solar cell, record‐high solar conversion efficiencies of 4.47 % and 6.4 % are achieved for C2H4 and C2+ products, respectively. This study provides an in‐depth understanding of the selective formation of C2+ products on Cu and paves the way for the practical application of electrocatalytic or solar‐driven CO2 reduction.
The facet effect of copper crystals to promote CO adsorption and C−C coupling and consequently yield a superior selectivity (87 % Faradaic efficiency) for C2+ products is described. Record‐high solar conversion efficiencies of 4.47 % and 6.4 % are achieved for C2H4 and C2+ products, respectively.
A N2 fixation by the electrocatalytic nitrogen reduction reaction from humidified air is regarded to be a critical tool for producing NH3 and reducing the globally accelerating CO2 emissions. ...Notwithstanding great efforts to improve catalyst activity and selectivity, promoting catalyst accessibility to high N2 concentrations to ensure that active sites fulfill their function should be a promising design direction. Here, Au nanoparticles are firmly anchored through atomic O on the surface of two-dimensional Ti3C2 using an ultrasound reduction process. Akin to the conspicuous role of the web in the predatory process of spiders, N2 adsorption experiments primarily suggest that a Ti3C2 “web” is beneficial for extraction of N2 from air, and embedding high valence-state Au clusters in the Ti3C2 “web” strengthens the chemical bonding effect toward N2 molecules. The high energy of N2 adsorption on the interface between gold clusters and Ti3C2 is the driving force for weakening triple NN bonds, and thereby the activation energy barrier is lowered via effective stabilization of N2H* species and destabilizing NH2NH2* under an alternative pathway. With Au loading content of ∼0.94%, Au/Ti3C2 exhibits an outstanding average yield of 30.06 μg h–1 mg–1 for NH3 production, with a high Faraday efficiency of 18.34% at −0.2 V.
The axially chiral indole-aryl motifs are present in natural products and biologically active compounds as well as in chiral ligands. Atroposelective indole formation is an efficient method to ...construct indole-based biaryls. We report herein the result of a chiral phosphoric acid catalyzed asymmetric cycloaddition of 3-alkynylindoles with azonaphthalenes. A class of indole-based biaryls were prepared efficiently with excellent yields and enantioselectivities (up to 98% yield, 99% ee). Control experiment and DFT calculations illustrate a possible mechanism in which the reaction proceeds via a dearomatization of indole to generate an allene-iminium intermediate, followed by an intramolecular aza-Michael addition. This approach provides a convergent synthetic strategy for enantioselective construction of axially chiral heterobiaryl backbones.
The grain boundary in copper-based electrocatalysts has been demonstrated to improve the selectivity of solar-driven electrochemical CO2 reduction toward multicarbon products. However, the approach ...to form grain boundaries in copper is still limited. This paper describes a controllable grain growth of copper electrodeposition via poly(vinylpyrrolidone) used as an additive. A grain-boundary-rich metallic copper could be obtained to convert CO2 into ethylene and ethanol with a high selectivity of 70% over a wide potential range. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy unveils that the existence of grain boundaries enhances the adsorption of the key intermediate (*CO) on the copper surface to boost the further CO2 reduction. When coupling with a commercially available Si solar cell, the device achieves a remarkable solar-to-C2-products conversion efficiency of 3.88% at a large current density of 52 mA·cm–2. This low-cost and efficient device is promising for large-scale application of solar-driven CO2 reduction.
Artificial photosynthesis can be used to store solar energy and reduce CO2 into fuels to potentially alleviate global warming and the energy crisis. Compared to the generation of gaseous products, it ...remains a great challenge to tune the product distribution of artificial photosynthesis to liquid fuels, such as CH3OH, which are suitable for storage and transport. Herein, we describe the introduction of metallic Cu nanoparticles (NPs) on Cu2O films to change the product distribution from gaseous products on bare Cu2O to predominantly CH3OH by CO2 reduction in aqueous solutions. The specifically designed Cu/Cu2O interfaces balance the binding strengths of H* and CO* intermediates, which play critical roles in CH3OH production. With a TiO2 model photoanode to construct a photoelectrochemical cell, a Cu/Cu2O dark cathode exhibited a Faradaic efficiency of up to 53.6 % for CH3OH production. This work demonstrates the feasibility and mechanism of interface engineering to enhance the CH3OH production from CO2 reduction in aqueous electrolytes.
Metallic copper nanoparticles were deposited on Cu2O films to change the product distribution of CO2 reduction in aqueous solution from the gaseous products generated on bare Cu2O to predominantly methanol. The carefully designed Cu/Cu2O interfaces balance the binding strengths of the H* and CO* intermediates, which enables efficient methanol production.
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