The development of cost-effective and highly active electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) for overall water splitting is still a big ...challenge. Herein, we design and construct a composite architecture that is composed of nitrogen-doped carbon encapsulating cobalt and molybdenum carbide nanoparticles (Co x Mo y @NC). Benefiting from synergistic cooperation between each component, the Co x Mo y @NC presents excellent performance towards both HER and OER catalysis in alkaline medium. The optimized electrocatalyst is found to be Co 4 Mo 2 @NC, which only requires relatively low overpotentials of ∼0.218 V and ∼0.33 V to produce a current density of 10 mA cm −2 for the electrocatalytic HER and OER, respectively. Such performance compares favorably to those of most previously reported Co, Mo-based electrocatalysts for water splitting. The present finding would enrich our knowledge to design and develop catalytically active molybdenum carbide-based electrocatalysts for overall water splitting.
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► Fabrication of biopolymer hydrogel stabilized silver nanoparticles is described. ► The Ag@AHs showed remarkable performance for catalytic reduction of 4-nitrophenol. ► The Ag@AHs ...can be easily separated and readily reused for catalytic application.
The direct use of macroscopic biopolymer alginate hydrogels (AHs) as a green and effective carrier to stabilize silver nanoparticles (Ag NPs) is presented. The Ag@AHs were characterized by UV–vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electronic microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The Ag@AHs showed excellent catalytic performance for the reduction of 4-nitrophenol by NaBH4 in aqueous solution, which can be easily separated after catalytic reaction and readily reused for three successive reaction cycles, attributing to the high stability of the Ag NPs supported by AHs. Our findings shed light on the design and fabrication of new heterogeneous catalyst with high performance based on the environmentally benign biopolymer hydrogel.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
• The graphene/Fe
3O
4 composite was synthesized by
in situ conversion of FeCl
3 to Fe
3O
4 and simultaneous reduction of GO into graphene in ethylene glycol solution. • The adsorption process was ...characterized by kinetics, isotherm and thermodynamic analysis. • The graphene/Fe
3O
4 composite could be utilized as a magnetically separable and efficient adsorbent for the environmental cleanup.
In this study, we have demonstrated a facile one-step solvothermal method for the synthesis of the graphene nanosheet (GNS)/magnetite (Fe
3O
4) composite. During the solvothermal treatment,
in situ conversion of FeCl
3 to Fe
3O
4 and simultaneous reduction of graphene oxide (GO) into graphene in ethylene glycol solution were achieved. Electron microscopy study suggests the Fe
3O
4 spheres with a size of about 200
nm are uniformly distributed and firmly anchored on the wrinkled graphene layers with a high density. The resulting GNS/Fe
3O
4 composite shows extraordinary adsorption capacity and fast adsorption rates for removal of organic dye, methylene blue (MB), in water. The adsorption kinetics, isotherms and thermodynamics were investigated in detail to reveal that the kinetics and equilibrium adsorptions are well-described by pseudo-second-order kinetic and Langmuir isotherm model, respectively. The thermodynamic parameters reveal that the adsorption process is spontaneous and endothermic in nature. This study shows that the as-prepared GNS/Fe
3O
4 composite could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Exploring efficient non-precious electrocatalysts with dual functionality for working in the same electrolyte towards both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is ...crucial for developing various devices for conversion, storage and usage of renewable energy. In this communication, we report a novel bifunctional electrocatalyst based on cobalt nanoparticles (NPs) embedded in porous N-rich carbon (PNC/Co) derived from a cobalt-containing metal-organic framework, which can serve as both active cathode and anode materials to drive the overall water splitting in alkaline media for the simultaneous electrogeneration of hydrogen and oxygen gases. In 1.0 M KOH electrolyte, the PNC/Co achieves small overpotentials at a current density of 10 mA cm super(-2) and yields high faradaic efficiency towards both the HER and OER. When fabricated as an alkaline water electrolyzer, the bifunctional PNC/Co affords 10 mA cm super(-2) at a cell voltage of 1.64 V.
Metal–organic frameworks (MOFs), a new class of porous crystalline materials, have attracted great interest as fascinating materials for sustainable energy and environmental remediation. However, the ...functionalization and diversification of MOFs are still challenging and imperative for the development of highly active MOF-based materials. Here, we present our recent finding on the design of a multifunctional MOF-based heterostructure composed of one-dimensional MIL–53(Fe) microrods with the magnetic nanospheres decoration (MHMCs), which can be easily fabricated by a one-pot solvothermal process. The MHMCs as a photoanode reveal a remarkable, steady and reproducible photocurrent response and exhibit effective photoelectrochemical performance toward water oxidation under visible light. Moreover, the MHMCs show high efficiency in a H 2 O 2 -mediated visible light photocatalysis process. The MHMCs/H 2 O 2 system exhibits enhanced apparent rate constants for the degradation of Rhodamine B (RhB) and p -nitrophenol (PNP), which are significantly higher than those of Fe 2 O 3 and Fe 3 O 4 photocatalysts, respectively, under visible light irradiation. This study provides new physical insights into the rational design of advanced MOF-based materials for energy and environmental applications.
The gradually dwindling resources of fossil fuels and the urgency to reduce greenhouse gas emissions portray a globally concerning image of our contemporary energy infrastructure with over reliance ...on coal, gas and oil. The transformation of the current fossil-fuel-based energy system to a more sustainable, renewable and cleaner alternative is desperately required to mitigate climate change. As a carbon-free and clean energy carrier, hydrogen has long been considered as a promising energy option. However, hydrogen does not exist naturally due to its inherently reactive features and has to be cost-effectively produced from hydrogen-containing compounds. Solar or electrochemically driven water splitting is an appealing vision for future sustainable hydrogen production. The state of the art water splitting technology
via
electro-catalysis is highly dependent on the efficiency of electrocatalysts to promote the oxygen evolution reaction (OER) or hydrogen evolution reaction (HER), a possible limiting step for the overall reaction. Electro-catalysts are currently dominated by these noble metals. To minimize the production cost, it is vital to develop noble-metal free catalysts for water splitting. In this context, metal nitrides have captured the imagination of academic researchers. This review summarizes the recent research progress made in these nanostructured metal nitrides as efficient and cheap catalysts for electrochemical and photo(electro)chemical water splitting. The various synthetic strategies for the fabrication and functionalization of these nanostructured metal nitrides are first presented followed by the introduction of their unique physical, chemical, and electronic properties and their respective applications in facilitating the HER, OER and the overall water splitting reaction. Some engineering perspectives to further enhance the performances of these nanostructured catalysts for water splitting are also discussed. Finally, opportunities for future development are briefly proposed.
This review summarizes the recent research progress made in nanostructured metal nitrides for electrochemical and photo(electro)chemical water splitting.
In this study, conductive Ti3C2 MXenes were used as a promoter to accelerate charger transfer of MoS2, realizing highly efficient HER electrocatalysis. A facile hydrothermal strategy is demonstrated ...to be effective for in situ growth of MoS2 nanosheets vertically standing on planar Ti3C2 nanosheets to form hierarchical heterostructures. Beneficial from the opened layer structures and strong interfacial coupling effect, the resulting MoS2/Ti3C2 heterostructures achieve a giant enhancement in HER activity compared with pristine MoS2 nanosheets. More specifically, the catalytic current density induced by MoS2/Ti3C2 heterostructures at an overpotential of ∼400 mV is nearly 6.2 times as high as that of the pristine MoS2 nanosheets. This work uncovers that the Ti3C2 nanosheets are ideal candidates for construction of highly active electrocatalysts for water splitting.
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•In situ growth of MoS2 nanosheets on Ti3C2 nanosheets was achieved.•Ti3C2 was used as a promoter to accelerate charger transfer of MoS2.•MoS2/Ti3C2 heterostructures achieved a greatly enhanced HER activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The development of efficient non-noble metal electrocatalysts for sustainable water splitting is crucial for clean energy conversion and has drawn extensive attention. Currently, nonprecious metal ...phosphides have emerged as efficient electrocatalysts to replace noble metals for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, it is still a great challenge for fabrication of universal, efficient and durable bifunctional electrocatalysts for these reactions via structural and component engineering. Herein, we report the design and construction of the hierarchical CoP–FeP branched heterostructures as high-performance and durable bifunctional electrocatalysts for both hydrogen and oxygen evolution electrocatalysis in various electrolytes. In such unique heterojunction, the intimate interfacial contact could induce built-in electric field at the interface, which effectively optimizes the surface electronic states of the FeP by the CoP, thus promoting the charge transfer and enhancing the electrocatalytic activity. As a consequence, the CoP–FeP heterostructures exhibit excellent performance for HER electrocatalysis, needing overpotentials as low as 30 and 71 mV to drive the 10 mA cm–2 current densities in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively, which are very close to that of Pt/C and rank it among the most HER-active electrocatalysts reported so far. Moreover, they can also behave as an efficient OER electrocatalyst with a very low overpotential of 250 mV at 10 mA cm–2 in 1.0 M KOH, outperforming most of the nonprecious-metal phosphides previously reported.
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The development of cheap and efficient electrocatalysts for promoting full water splitting is still challenging. Here, we report a composite architecture that consists of onion-like ultrathin ...graphene shells encapsulating uniform metallic nickel nanoparticles (Ni@graphene) derived by a straightforward thermal treatment of a Ni-based metal–organic framework in an inert atmosphere. The resulting Ni@graphene is highly catalytically active for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1.0 M KOH solutions. It only requires relatively low overpotentials (OER ∼ 370 mV; HER ∼ 240 mV) to yield a catalytic current of 10 mA/cm2, which compares favorably to most previously reported Ni-based elecrocatalysts for water splitting. The excellent performance would be attributed to the catalytic sites of metallic Ni and the intact metal protection effect of the outer graphene layers.
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Developing robust earth-abundant electrocatalysts for oxygen evolution reaction (OER) is an ongoing scientific challenge, which is coupled with a number of important electrochemical processes and ...many key renewable energy systems, such as water splitting, rechargeable metal–air batteries, and regenerative fuel cells. Here, we proposed a rational design and fabrication of the synergetic coaxial nanocable structures by intimate growth of the layered nickel–cobalt silicate hydroxide nanosheets on the outer surfaces of multiwalled carbon nanotubes (MWCNTs@NCS) and demonstrated their high efficiency in electrocatalytic OER from water splitting. The electrocatalytic activities of the MWCNTs@NCS were found to be significantly higher than that of bare NCS and pristine MWCNTs, synergetically determining by such the constituted individual components. Among them, the MWCNTs@NCS-2 exhibited best electrocatalytic OER performance, showing a small OER onset potential, large anodic current and long-term durability, which was favorably comparable to the previously reported NiCo-based OER electrocatalysts in alkaline electrolytes. To the best of our knowledge, this was a first example on the earth-abundant metal silicate hydroxides utilized in electrochemical water splitting.
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