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 in 0.5 M HSO 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. 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 at the low voltage of 1.6 V, demonstrating its potential for practical overall water splitting without the use of noble metals.
The layered molybdenum chalcogenide MoS 2 has attracted wide attention due to its potential electrochemical applications. Based on its unique physical and chemical properties, numerous advances have shown that nanostructured MoS 2 , 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, MoS 2 could be used as an effective substitute for noble metals. Meanwhile, MoS 2 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, MoS 2 -based electrochemical devices have been applied as sensors for a variety of chemicals.In this review, we summarize recent advances in the development of MoS 2 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 MoS 2 , 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 MoS 2 in the future.
Broader contextThe development of inexhaustible and clean energy technologies has far-reaching benefits for our society. Owing to its high anisotropy and unique crystal structure, the attractive properties of 2D molybdenum disulfide (MoS 2 ) can be utilized in a variety of energy conversion and storage (ECS) applications. Therefore, understanding how these properties can be tuned and the tunable properties can be utilized becomes increasingly important. In this review, we first summarize recent synthetic strategies toward preparation of MoS 2 with different structures, and its role in several important renewable energy technologies. We then discuss the relationship between the tuned properties and the performance of MoS 2 in different applications, emerging trends during their development, and challenges facing them, offering our perspectives on how to effectively advance the development of MoS 2 -based devices.
In this study, the synthesis of zeolitic imidazole framework (ZIF-8) in water was systematically studied using 6 zinc sources (Zn(OAc) 2 , ZnSO 4 , Zn(NO 3 ) 2 , ZnCl 2 , ZnBr 2 , ZnI 2 ), respectively, under different conditions at room temperature without using any additives. It was found that Zn(OAc) 2 is the best precursor and the resultant ZIF-8 particles have the best quality with rhombic dodecahedron morphology. The concentration of 2-methylimidazole (Hmim), molar ratio Hmim/Zn and water content all have significant impacts on the morphology, particle size, and crystallinity of ZIF-8. Further result analysis reveals that 3 key reactions are involved in the ZIF-8 formation which needs five steps in ZIF-8 structural evolution.This study provides a deep understanding of the crystallization process of ZIF-8 particles in a waterbased system.
In this paper, the comparison of activated carbon fiber (ACF) felt and graphite cathode suggested H 2 O 2 might effectively be electrogenerated from O 2 reduction on the large surface area ACF felt cathode, this was more adaptive for electro-Fenton process. The removal of color and total organic carbon (TOC) from simulated dye wastewater containing Acid Red 14 (AR14) was experimentally investigated using electro-Fenton reaction with ACF cathode. After 360 min of electrolysis and under the operation conditions of 0.36 A current, 1 mM Fe 2C at pH 3, 70% TOC was removed as well as complete decolorization occurred. The effect of Fe 2C ion concentration and applied current were also studied in detail in the experimental runs.
This study intends to reinvent classical Fenton chemistry by enabling the Fe(II)/Fe(III) redox cycle to occur on a newly developed FeOCl nanosheet catalyst for facile hydroxyl radical ( • OH) generation from H 2 O 2 activation. This approach overcomes challenges such as low operating pH and large sludge production that have prevented a wider use of otherwise attractive Fenton chemistry for practical water treatment, in particular, for the destruction of recalcitrant pollutants through nonselective oxidation by • OH. We demonstrate that FeOCl catalysts exhibit the highest performance reported in the literature for • OH production and organic pollutant destruction over a wide pH range. We further elucidate the mechanism of rapid conversion between Fe(III) and Fe(II) in FeOCl crystals based on extensive characterizations. Given the low-cost raw material and simple synthesis and regeneration, FeOCl catalysts represent a critical advance toward application of iron-based advanced oxidation in real practice.
CuFe 2 O 4 /activated carbon magnetic adsorbents, which combined the adsorption features of activated carbon with the magnetic and the excellent catalytic properties of powdered CuFe 2 O 4 , were developed using a simple chemical coprecipitation procedure. The prepared magnetic composites can be used to adsorb acid orange II (AO7) in water and subsequently, easily be separated from the medium by a magnetic technique. CuFe 2 O 4 /activated carbon magnetic adsorbents with mass ratio of 1:1, 1:1.5 and 1:2 were prepared. Magnetization measurements, BET surface area measurements, powder XRD and SEM were used to characterize the prepared adsorbents. The results indicate that the magnetic phase present is spinel copper ferrite and the presence of CuFe 2 O 4 did not significantly affect the surface area and pore structure of the activated carbon. The adsorption kinetics and adsorption isotherm of acid orange II (AO7) onto the composites at pH 5.2 also showed that the presence of CuFe 2 O 4 did not affect the adsorption capacity of the activated carbon. The thermal decomposition of AO7 adsorbed on the activated carbon and the composite was investigated by in situ FTIR, respectively. The results suggest that the composite has much higher catalytic activity than that of activated carbon, attributed to the presence of CuFe 2 O 4 . The variation of the adsorption capacity of the composites after several adsorption-regeneration cycles has also been studied.
Efficient and sustainable Fe–N–C catalyst prepared by EDTA–Fe(ii) pyrolysis promotes the ORR performances within a nearly four-electron transfer pathway.
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