Interfacial engineering and elemental doping are the two parameters to enhance the catalytic behavior of cobalt nitrides for the alkaline hydrogen evolution reaction (HER). However, simultaneously ...combining these two parameters to improve the HER catalytic properties of cobalt nitrides in alkaline media is rarely reported and also remains challenging in acidic media. Herein, it is demonstrated that high‐valence non‐3d metal and non‐metal integration can simultaneously achieve Co‐based nitride/oxide interstitial compound phase boundaries on stainless steel mesh (denoted Mo‐Co5.47N/N‐CoO) for efficient HER in alkaline and acidic media. Density functional theory (DFT) calculations show that the unique structure does not only realize multi‐active sites, enhanced water dissociation kinetics, and low hydrogen adsorption free energy in alkaline media, but also enhances the positive charge density of hydrogen ions (H+) to effectively allow H+ to receive electrons from the catalysts surface toward promoting the HER in acidic media. As a result, the as‐prepared Mo‐Co5.47N/N‐CoO demands HER overpotential of −28 mV@10 mA cm−2 in an alkaline medium, and superior to the commercial Pt/C at a current density > 44 mA cm−2 in acidic medium. This work paves a useful strategy to design efficient cobalt‐based electrocatalysts for HER and beyond.
Herein, a non‐3d metal (Mo) and non‐metal nitrogen (N) doping strategy could facilitate the formation of 3D porous terrace‐like in situ Mo‐Co5.47N/N‐CoO heterojunctions on stainless steel mesh. The optimized catalyst achieves simultaneous modulation of active site number, water dissociation, and hydrogen adsorption free energy in both alkaline and acidic electrolytes.
The ever‐growing portable electronics and electric vehicle draws the attention of scaling up of energy storage systems with high areal‐capacity. The concept of thick electrode designs has been used ...to improve the active mass loading toward achieving high overall energy density. However, the poor rate capabilities of electrode material owing to increasing electrode thickness significantly affect the rapid transportation of ionic and electron diffusion kinetics. Herein, a new concept named “sub‐thick electrodes” is successfully introduced to mitigate the Li‐ion storage performance of electrodes. This is achieved by using commercial nickel foam (NF) to develop a monolithic 3D with rich in situ heterogeneous interfaces anode (Cu3P‐Ni2P‐NiO, denoted NF‐CNNOP) to reinforce the adhesive force of the active materials on NF as well as contribute additional capacity to the electrode. The as‐prepared NF‐CNNOP electrode displays high reversible and rate areal capacities of 6.81 and 1.50 mAh cm−2 at 0.40 and 6.0 mA cm−2, respectively. The enhanced Li‐ion storage capability is attributed to the in situ interfacial engineering within the NiO, Ni2P, and Cu3P and the 3D consecutive electron conductive network. In addition, cyclic voltammetry, charge–discharge curves, and symmetric cell electrochemical impedance spectroscopy consistently reveal improved pseudocapacitance with enhanced transports kinetics in this sub‐thick electrodes.
A new concept termed “sub‐thick electrode” is introduced to address the poor transport kinetics by reinforcing the adhesive force of active materials on NF current collector as well as contributing extra capacity to the electrode. The optimized electrode displayed high initial and reversible areal capacity of 10.31 and 7.46 mAh cm−2 at 0.4 mA cm−2 due to enhanced transport kinetics.
Photoelectrochemical water splitting based on nanostructured bismuth vanadate (BiVO4) can be a promising strategy to produce low‐cost and green H2 to replace fossil fuels and realize carbon ...neutrality. Herein, a simple chemical way to realize in situ carbon doping into BiVO4 crystalline structure is designed and obtained carbon‐doped BiVO4, namely C‐BiVO4, can improve the electronic conductivity of BiVO4. In addition, the introduction of the synthesized carbon quantum dots (CQDs) as a co‐catalyst, immobilizes CQDs onto the C‐BiVO4 nanosheet and acquires the optimized C‐BiVO4/CQDs heterogeneous structure, which not only boosts light absorption, but also enhances the separation and transfer of the photo‐generated charges. Stemming from the dual carbon actions, the as‐prepared C‐BiVO4/CQDs photoanode exhibits an excellent photocurrent density of 4.83 mA cm−2 at 1.23 V versus the RHE without the use of any hole scavengers. To assure the practical application of the sensitive photocatalyst, a polyaniline layer is electroplated onto the C‐BiVO4/CQDs catalyst as a conducting, electroactive, and protective layer to sustain a remarkable long‐term photocurrent density of 2.75 mA cm−2 for 9 hours. This work suggests that the proposed low‐cost, environmentally friendly dual carbon actions can modify photocatalyst and achieve green production of H2.
The authors demonstrate that nonmetallic carbon materials can significantly improve the photoelectrochemical water oxidation performance of bismuth vanadate (BiVO4). The resulting C‐doped BiVO4/carbon quantum dots photoanode exhibits excellent photocurrent density of 4.83 mA cm−2 at 1.23 V versus the RHE without any hole scavenger.
In this work, we developed ternary metallic cobalt-cobalt nitride-dicobalt phosphide composite embedded in nitrogen and phosphorus co-doped carbon (Co/CoN/Co2P-NPC) as bifunctional catalysts for ...hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The as-prepared Co/CoN/Co2P-NPC is achieved by simultaneous annealing and phosphating of a Co–N rich metal-organic frameworks (MOFs) precursor. Compare with the phosphorus-free Co/CoN embedded nitrogen-doped carbon electrocatalyst (Co/CoN-NC), the as-prepared Co/CoN/Co2P-NPC display superior HER and OER low overpotential of 99 mV and 272 mV at current density of 10 mA cm−2. When Co/CoN/Co2P-NPC electrocatalyst is use as bifunctional catalysts in overall alkaline water splitting, it exhibit excellent behaviour with 10 mA cm−2 current at overall cell potential of 1.60 V. The excellent performance of Co/CoN/Co2P-NPC electrocatalyst is attributed to the phosphating process that could further enhance synergistic effect, create stronger electronic interactions, and form efficient dual heteroatom doping to optimize the interfacial adhesion within the electrocatalyst. This present work will create more opportunities for the development of new, promising and more active sites electrocatalysts for alkaline electrolysis.
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•Co/CoN/Co2P composite is embedded in N and P co-doped carbon by one-step synthesis.•The synthesize involve one-step annealing and phosphorization of Co-based MOF.•The composite is used as bifunctional OER and HER electrocatalysts.•The composite exhibit excellent performance owing to the multiple active sites.•Overall water splitting based on the composite achieve 10 mA cm−2 overall voltage of 1.60 V.
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•Core-double-shell architecture was designed as efficient HER and OER electrocatalysts.•Cobalt phosphide and NiFe-LDH were used as representative HER and OER catalysts.•The ...architecture consist of core–shell porous carbon fiber (CFC@EC) and TMCs.•Lattice distortions were created in the TMCs by CFC@EC, facilitating the exposure of active sites.•Enhanced performance is due to the strong electronic interaction between the hybrids.
Different transition metal compounds (TMCs) nanostructures grown on conductive substrates have been considered as promising self-supportive non-precious electrocatalysts for electrochemical water splitting, but extremely challenging to develop facile and generalized approaches for rational design and enhancing their catalytic properties. Herein, we develop a general strategy to boost the hydrogen and oxygen evolution reactions (HER and OER) performance of TMCs by designing monolith electrocatalyst architectures. The monoliths comprises of TMCs integrated on carbon fiber cloth core–shell (CFC@EC) structure. The CFC@EC allows the creation of numerous lattice distortions and strong electronic interactions between CFC@EC and metal cations of the TMCs. Such lattice distortions exposes more active sites in CFC@EC/TMCs compared to the pristine CFC coated TMCs (CFC/TMC). Cobalt phosphide (CoP) nanowires and NiFe-LDH coated on CFC@EC exhibits the optimized HER and OER activities. Overall water splitting device assembled based on the optimized HER and OER electrodes also achieve low overall potential of 1.53 V at 10 mA cm−2. More importantly, we further experimentally verify that the integration of Ni3N and Ni3S2, CoS2, NiCo-LDH, NiMn-LDH with CFC@EC also reveal similar improved performance, providing a general and valuable strategy into the design of other self-supporting electrocatalysts for water splitting and beyond.
Here, the concept of thick electrode is utilized to design a-17 mm three-dimensional (3D) all-carbon frameworks with remarkable structural stability as high-areal-capacity anode for lithium-ion ...batteries (LIBs). The framework involves the rational design of graphite fibers (GFs) bonded with pyrolytic carbon (PC) and graphite nanoplatelets (GNP), offering a unique architecture and a scalable production approach. The as-fabricated 3D-GF/PC/GNP electrode with a high mass loading of ≈30 mg cm−2 can deliver an unexpected high initial and reversible areal capacity of 23.53 and 11.63 mA h cm−2 at current density of 2.0 mA cm−2, impressive rate performance and cyclic stability. Both theoretical simulations and experimental analyses show that the excellent performance of the electrode can be attributed to the incorporation of GNP that modulates the electronic conductivity of the framework, enabling easier Li-ion intercalation/deintercalation pathway to promote the pseudocapacitive and surface adsorption Li-ion storage.
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•Ultrathick 3D all-carbon frameworks which consist of GFs bonded with PC and GNP was designed.•The 3D carbon frameworks deliver an unexpected high-areal-capacity of 23.53 mAh cm-2 at 2.0 mA cm-2.•The excellent performance is attributed to the GNPs, enhancing the conductivity and Li-ion storage surface adsorption.
Interfacial engineering and electronic modulation are some of the main components for enhancing the catalytic activity of electrocatalysts towards achieving efficient water splitting. Iron nitrides ...exhibit mediocre oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their unsuitable d‐band energy level. In this work, we strongly boost the HER and OER catalytic performance of Fe2N for the first time by doping Co and Al, which could not only induce the formation of Fe2N/Fe3N hybrid interface but also tune the d‐band center position. The CoAl−Fe2N/Fe3N nanoparticles display HER and OER overpotential of 145 and 307 mV at 10 mA/cm2. XPS and DFT calculations confirm that tailoring the d‐band center position and interfacial engineering facilitates strong electronic interactions between Fe2N and Fe3N, synergistically optimize the electronic structure, which enriches H and H2O adsorption energy and oxygen‐containing intermediates. An alkaline electrolyzer based on CoAl−Fe2N/Fe3N requires an overall potential of 1.67 V at 10 mA/cm2, demonstrating the use of iron nitrides as a bifunctional electrocatalyst for water splitting activity.
Electrocatalysis: Fe2N is endows with enhanced HER and OER catalytic activities not only by tuning the d‐band center positions but also formation of Fe2N/Fe3N interface as a result of dual doping with Co and Al. The dual‐doped Fe2N/Fe3N display HER and OER overpotential of 145 and 307 mV at 10 mA/cm2 and significantly better than Fe2N (461 and 451 mV) and individual Co‐ and Al‐doped Fe nitride catalysts.
Cobalt nitride electrocatalysts have been investigated and proven to show excellent oxygen evolution reaction activity owing to their excellent metallic properties, but their hydrogen evolution ...reaction (HER) properties are rarely reported because of their unsatisfactory molecular energy level, especially the d-orbital. Herein, taking Co
N as a case study, we tune the d-orbital of metallic Co
N nanowires via rapid formation of iron oxyhydroxide (FeOOH). Experimental analyses show that FeOOH@Co
N/SSM exhibits excellent HER catalytic activity with considerable low onset overpotential (22 mV), small Tafel slope (34 mV dec
), and excellent stability at current densities ranging from 20 to 100 mA cm
. Additionally, theoretical assessments display that the hybridization of Co
N with FeOOH is beneficiary for optimizing and promoting the free energy of H adsorption due to the tuning of d-orbital. An overall water-splitting device assembled based on bifunctional FeOOH@Co
N/SSM delivers an onset potential of 1.48 V with excellent stability up to 4 days. This shows a new strategy for designing a high-performance water-splitting device based on cobalt-based electrocatalysts.
Cobalt nitride electrocatalysts have been investigated and proven to show excellent oxygen evolution reaction activity owing to their excellent metallic properties, but their hydrogen evolution ...reaction (HER) properties are rarely reported because of their unsatisfactory molecular energy level, especially the d-orbital. Herein, taking Co4N as a case study, we tune the d-orbital of metallic Co4N nanowires via rapid formation of iron oxyhydroxide (FeOOH). Experimental analyses show that FeOOH@Co4N/SSM exhibits excellent HER catalytic activity with considerable low onset overpotential (22 mV), small Tafel slope (34 mV dec–1), and excellent stability at current densities ranging from 20 to 100 mA cm–2. Additionally, theoretical assessments display that the hybridization of Co4N with FeOOH is beneficiary for optimizing and promoting the free energy of H adsorption due to the tuning of d-orbital. An overall water-splitting device assembled based on bifunctional FeOOH@Co4N/SSM delivers an onset potential of 1.48 V with excellent stability up to 4 days. This shows a new strategy for designing a high-performance water-splitting device based on cobalt-based electrocatalysts.
Cobalt oxide (Co3O4) delivers a poor capacity when applied in large-sized alkali metal-ion systems such as potassium-ion batteries (KIBs). Our density functional theory calculation suggests that this ...is due to poor conductivity, high diffusion barrier, and weak potassium interaction. N-doped carbon can effectively attract potassium ions, improve conductivity, and reduce diffusion barriers. Through interface engineering, the properties of Co3O4 can be tuned via composite design. Herein, a Co3O4@N-doped carbon composite was designed as an advanced anode for KIBs. Due to the interfacial design of the composite, K+ were effectively transported through the Co3O4@N–C composite via multiple ionic pathways. The structural design of the composite facilitated increased Co3O4 spacing, a nitrogen-doped carbon layer reduced K-ion diffusion barrier, and improved conductivity and protected the electrode from damage. Based on the entire composite, a superior capacity of 448.7 mAh/g was delivered at 50 mA/g after 40 cycles, and moreover, 213 mAh/g was retained after 740 cycles when cycled at 500 mA/g. This performance exceeds that of most metal-oxide-based KIB anodes reported in literature.
