Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster ...anchored on a trace P‐doped defective TiO2 substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1 at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity.
A ruthenium cluster anchored on a lightly P‐doped defective TiO2 catalyst was designed for the electrochemical hydrogen evolution reaction in alkaline electrolyte. The surface oxygen vacancies enhanced water dissociation and P‐doping facilitated the H2 generation by enabling hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity.
Developing robust electrocatalysts and advanced devices is important for electrochemical carbon dioxide (CO2) reduction toward the generation of valuable chemicals. We present herein a ...carbon‐confined indium oxide electrocatalyst for stable and efficient CO2 reduction. The reductive corrosion of oxidative indium to the metallic state during electrolysis could be prevented by carbon protection, and the applied carbon layer also optimizes the reaction intermediate adsorption, which enables both high selectivity and activity for CO2 reduction. In a liquid‐phase flow cell, the formate selectivity exceeds 90 % in a wide potential window from −0.8 V to −1.3 V vs. RHE. The continuous production of ca. 0.12 M pure formic acid solution is further demonstrated at a current density of 30 mA cm−2 in a solid‐state electrolyte mediated reactor. This work provides significant concepts in the parallel development of electrocatalysts and devices for carbon‐neutral technologies.
A robust carbon‐covered indium oxide electrocatalyst demonstrates an enhanced and stable activity for the direct production of formic acid in a solid‐state carbon dioxide electrolyzer.
Electrochemical N2 reduction in aqueous solutions at ambient conditions is extremely challenging and requires rational design of electrocatalytic centers. We demonstrate a boron-doped graphene as an ...efficient metal-free N2 reduction electrocatalyst. Boron doping in the graphene framework leads to redistribution of electron density, where the electron-deficient boron sites provide enhanced binding capability to N2 molecules. Density functional theory calculations reveal the catalytic activities of different boron-doped carbon structures, in which the BC3 structure enables the lowest energy barrier for N2 electroreduction to NH3. At a doping level of 6.2%, the boron-doped graphene achieves a NH3 production rate of 9.8 μg·hr−1·cm−2 and one of the highest reported faradic efficiencies of 10.8% at −0.5 V versus reversible hydrogen electrode in aqueous solutions at ambient conditions. This work suggests the strong potential of atomic-scale design for efficient electrocatalysts for N2 reduction.
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•DFT data showed that B doping led to electron redistribution and better N2 adsorption•Experiments and DFT data revealed that BC3 enabled the lowest energy barrier for NRR•Excellent NH3 production rate and faradic efficiency were achieved at −0.5 V versus RHE
Ammonia (NH3) is an essential chemical that is widely used in agriculture and industry applications. The industry-scale Haber-Bosch process accounts for ∼1.5% of global energy consumption and a significant CO2 emission annually, due to the extreme inertness of N2 and carbon emission for producing H2 precursor. The electrochemical reduction of N2 (NRR) in aqueous solutions at ambient conditions is extremely challenging and requires rational design of electrocatalytic centers. Previous reports predominantly used metal-based electrocatalysts, and the efficiency has generally been extremely low. In this work, we demonstrate for the first time boron-doped graphene as an efficient metal-free NRR electrocatalyst in aqueous solutions at ambient conditions.
Boron-doped graphene with different boron structures was rationally synthesized to enhance the adsorption of N2, thus enabling an efficient metal-free electrocatalyst for electrochemical N2 reduction in aqueous solution at ambient conditions. At a doping level of 6.2%, boron-doped graphene achieved a NH3 production rate of 9.8 μg·hr−1·cm−2 and an excellent faradic efficiency (10.8% at −0.5 V versus reversible hydrogen electrode).
Nanomaterials are being widely considered as electrocatalyst for the production of hydrogen nowadays. Due to their outstanding catalytic performance, research activities are ongoing to explore the ...efficient electrocatalyst. This review article will be focused on recent challenges and progression in developing the metal and metal-free electrocatalyst for HER/OER activity.
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•Mechanisms of HER and OER reaction in both acidic and alkaline medium were discussed.•Multi-metallic alloy, oxides and hydroxides are promising electrocatalyst for HER/OER.•Nanomaterials having amorphous structure possess better catalytic efficiency.•Transitional metal doped MOFs are found to be more promising for HER activity.
Electrocatalytic water splitting is considered being an optimistic process and can be a sustainable source of renewable energy for the future. Although, the primary overpotential requirement and stability problem of the electrocatalysts make the process difficult for industrial applications, a cost-effective electrocatalyst with high surface area, stability, and bifunctional activity can eliminate such barriers in the upcoming eons. To date, metal alloys, metal hydroxides, metal oxides, metal derivatives (phosphides, sulfides, selenides, and carbides) metal–organic frameworks, hybrid and metal-free materials based electrocatalysts have been already developed for the overall water splitting. Herein, the challenges to enhance the activity, stability and durability in the metal (both noble metal and transitional metal) and metal-free based electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are summarized. A general overview of the water splitting mechanism followed by various electrocatalyst are discussed mainly. Moreover, it is expected to provide a comprehensive summary and outlook at the end.
Chemical doping of reduced graphene oxide (rGO) oxide has been a major trend as photocatalyst and electrocatalyst owing to large number of active sites they bring in. In the present work ternary ...copper iron sulphide (Cu5FeS4) has been successfully synthesized using hydrothermal method and incorporated with rGO, N/rGO and B/rGO. The structural, morphological and compositional changes were analyzed using XRD, XPS, SEM, TEM and EDAX results respectively. The bandgap of the materials was confirmed using UV-DRS results. The photoluminescence (PL) spectra of the samples revealed the reduction of recombination with the presence of rGO and doped rGO. The photocatalytic studies of the composites were carried out using methylene blue(MB) as a model pollutant where CFS-N/rGO shows the highest degradation rate of 70%.The electrocatalytic tests were conducted in order to study the performance of the composites as catalyst for HER where CFS-N/rGO showed an enhanced activity with higher current density and lower Tafel slope.The higher Cdl value of CFS-N/rGO indicates the increased number of exposed active sites when doped with N/rGO. The results indicate a considerable amount of change in the photocatalytic and electrocatalytic properties of CFS when doped with rGO, B/rGO and N/rGO.
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•Cu5FeS4 (CFS) catalyst was prepared via hydrothermal method.•The as-synthesized particles were added with rGO, N/rGO and B/rGO (CFS-rGO, CFS N/rGO, CFS-B/rGO).•CFS-N/rGO exhibits superior electrocatalytic activity towards HER and photocatalytic activity for dye degradation.
In the 21st century, the rapid development of human society has made people's demand for green energy more and more urgent. The high-energy-density hydrogen energy obtained by fully splitting water ...is not only environmentally friendly, but also is expected to solve the problems caused by the intermittent nature of new energy. However, the slow kinetics and large overpotential of the oxygen evolution reaction (OER) limit its application. The introduction of Te element is expected to bring new breakthroughs. With the least electronegativity among the chalcogens, the Te element has many special properties, such as multivalent states, strong covalentity, and high electrical conductivity, which make it a promising candidate in electrocatalytic OER. In this review, we introduce the peculiarities of Te element, summarize Te doping and the extraordinary performance of its compounds in OER, with emphasis on the scientific mechanism behind Te element promoting the OER kinetic process. Finally, challenges and development prospects of the applications of Te element in OER are presented.
Developing earth-abundant-electrocatalysts for oxygen evolution reaction is one of the promising ways to achieve efficient water-splitting for hydrogen production (a clean chemical fuel). This paper ...reviews the activity, stability and durability for oxygen evolution reaction in alkaline medium of different types of recently reported electrocatalysts such as Ni, Co, NiCo, Fe, Se, Mo, Cu, Mn, Zn, V, Ti/Ta, and metal free based earth-abundant-electrocatalysts. Further, this paper reviews the strategies used to achieve the remarkably low overpotential (including η10: ≤100 mV), high long term stability (including ≥100 h) and high durability (including ≥5000 cycles) of earth-abundant-electrocatalysts for oxygen evolution reaction in alkaline medium and those are better or well comparable with the state-of-the-art IrO2 electrocatalyst2. Finally, this paper summarizes the efficient strategies such as preparing porous or nanostructured materials, preparing quantum sized materials, doping metals or heteroatoms, tuning the optimal crystal structure, preparing bimetallic/multi-metallic materials, preparing materials with oxygen vacancies/defects, preparing amorphous materials, preparing metal chalcogenides, preparing metal oxy hydroxides, and integrating electrocatalysts with carbon to enhance the activity, stability, and durability for OER.
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•Earth-abundant-electrocatalysts for OER in alkaline medium are reviewed.•The electrocatalysts exhibit remarkably higher activity for OER than IrO2.•The electrocatalysts exhibit remarkably higher stability for OER than IrO2.•The electrocatalysts exhibit remarkably high durability for OER.•Strategies used to achieve high performance of electrocatalysts for OER are reviewed.
Developing earth-abundant-electrocatalysts for hydrogen evolution reaction is one of the promising ways to achieve efficient water-splitting for hydrogen production (a clean chemical fuel). This ...paper reviews the activity, stability and durability for hydrogen evolution reaction in alkaline medium of different types of recently reported potential electrocatalysts such as Ni, Co, NiCo, Fe, Cu, W, Mo, Se, Mn, Zn, V, and metal free based earth-abundant-electrocatalysts. Further, this paper reviews the strategies used to achieve the remarkably low overpotential (including η10: ≤ 35 mV), high long term stability (including ≥ 100 h) and high durability (including ≥ 5000 cycles) of potential earth-abundant-electrocatalysts for hydrogen evolution reaction in alkaline medium and those are better or well comparable with the state-of-the-art, noble, Pt/C electrocatalyst. Finally, this paper summarizes the efficient strategies such as preparing porous structured materials, preparing nanostructured materials with superaerophobic surface, preparing nanostructured materials, preparing carbon composites/integrating electrocatalysts with carbon, preparing amorphous materials, preparing materials with oxygen vacancies/defects, preparing metal chalcogenides, preparing bimetallic/multi-metallic materials, doping metals or heteroatoms, preparing electrocatalysts with core-shell structure, decorating electrocatalysts with amines, preparing homo-junction/heterojunction structured materials, preparing hollow structured materials, and preparing boron-rich surface to enhance the activity, stability, and durability for HER.
Display omitted The strategies used to achieve the significantly low overpotential, high long term stability and high durability of potential earth-abundant-electrocatalysts for hydrogen evolution reaction in alkaline medium have been reviewed.
Developing high‐performance and cost‐effective bifunctional electrocatalysts for large‐scale water electrolysis is desirable but remains a significant challenge. Most existing nano‐ and ...micro‐structured electrocatalysts require complex synthetic procedures, making scale‐up highly challenging. Here, a heterogeneous Ni2P‐Fe2P microsheet is synthesized by directly soaking Ni foam in hydrochloric acid and an iron nitrate solution, followed by phosphidation. Benefiting from high intrinsic activity, abundant active sites, and a superior transfer coefficient, this self‐supported Ni2P‐Fe2P electrocatalyst shows superb catalytic activity toward overall water splitting, requiring low voltages of 1.682 and 1.865 V to attain current densities of 100 and 500 mA cm−2 in 1 m KOH, respectively. Such catalytic performance is superior to the benchmark IrO2 || Pt/C pair and also places this electrocatalyst among the best bifunctional catalysts reported thus far. Furthermore, its enhanced corrosion resistance and hydrophilic surface make it suitable for seawater splitting. It is able to achieve current densities of 100 and 500 mA cm−2 in 1 m KOH seawater at voltages of 1.811 and 2.004 V, respectively, which, together with its robust durability, demonstrates its great potential for realistic seawater electrolysis. This work presents a general and economic approach toward the fabrication of heterogeneous metallic phosphide catalysts for water/seawater electrocatalysis.
A novel and economic strategy is developed to synthesize heterogeneous bimetallic phosphide Ni2P‐Fe2P as an efficient bifunctional catalyst for water/seawater splitting. Benefiting from high intrinsic activity, abundant active sites, and a superior transfer coefficient, this self‐supported Ni2P‐Fe2P electrocatalyst shows superb catalytic activity toward overall water splitting, together with its robust durability.
Tuning the crystal phase of metal alloy nanomaterials has been proved a significant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully ...developed a simple strategy to controllably synthesize a rare crystal structure of hexagonal close‐packed (hcp) NiFe nanoparticle (NP) encapsulated in a N‐doped carbon (NC) shell (hcp‐NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions, in which the hcp‐NiFe@NC exhibits superior OER activity compared to the conventional face‐centered cubic (fcc) NiFe encapsulated in a N‐doped carbon shell (fcc‐NiFe@NC). At the current densities of 10 and 100 mA cm−2, the hcp‐NiFe@NC with Fe/Ni ratio of ≈5.4 % only needs ultralow overpotentials of 226 mV and 263 mV versus reversible hydrogen electrode in 1.0 m KOH electrolyte, respectively, which were extremely lower than those of fcc‐NiFe@NC and most of other reported NiFe‐based electrocatalysts. We proposed that hcp‐NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER. This research provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
Hcp‐NiFe alloy nanoparticles encapsulated in N‐doped carbon shells (hcp‐NiFe@NC) were successfully synthesized through a facile MOF‐annealing strategy. Benefiting from the crystal structure and electronic property, the hcp‐NiFe@NC exhibits outstanding OER performance over the conventional fcc‐NiFe@NC catalyst.
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