Efficient Electrocatalysts Research Articles

Enhanced oxygen evolution reaction performance using amorphous hollow cerium-doped cobalt phosphate derived from ZIF-67 structures

A major obstacle in achieving massive operations water splitting is the slow rate of the anodic reaction. To address this issue, metal phosphates have been extensively employed as efficient materials for the oxygen evolution reaction (OER). In this study, ZIF-67 structures were synthesized in both single-metal and bimetallic forms with different molar ratios of cerium. The structure with the best electrochemical activity ((5 present) cerium doped ZIF-67 ((5)CeZIF-67)) was subjected to a phosphatization process, resulting in the formation of the amorphous and hollow cerium doped cobalt phosphate (Ce-CPO) structure as a novel and highly efficient OER electrocatalyst. To the best of authors knowledge, this is the first report on the synthesis and application of Ce-CPO structure for boosting OER process. This resultant structure exhibited suitable electrochemical performance in the oxygen evolution reaction (OER), achieving an overpotential of 286 mV at a current density of 30 mA cm−2 and a Tafel slope of 74.4 mV decade−1. Furthermore, the final structure demonstrated satisfactory stability during a 10 h operation period. The notable improvement in the Ce-CPO structure was due to the use of a bimetallic framework combined with phosphorus and an amorphous porous structure. The distinctive configuration achieved greatly amplifies the effective surface area, hence improving electron transfer. The findings of this research can contribute to the development of electrodes with improved performance in OER.

Accelerated Electrons Transfer and Synergistic Interplay of Co and Ge Atoms (111 Crystal Plane) Activated by Anchoring Nano Spinel Structure Co2GeO4 onto Carbon Cloth Composite Electrocatalyst for Highly Enhanced Hydrogen Evolution Reaction

The electrochemical hydrogen evolution reaction (HER) was considered to be a promising strategy for future clean energy. In this work, a composite electrocatalyst (designated as CGO36@CC) was synthesized through anchoring of nano spinel structure Co2GeO4 onto carbon cloth fibers and exhibited outstanding electrocatalytic performance for HERs in an alkaline medium. The characterization outcome established that, after 36 h of hydrothermal reaction, nano spinel structure Co2GeO4 particles (exposed abundant 111 crystal planes) were stably loaded onto a carbon cloth fiber surface, and this structural configuration facilitated the electrons transferring between each other. In addition, the electrochemical analysis revealed that the incorporation of nano spinel structure Co2GeO4 and carbon cloth significantly augmented the electrochemical activity value of the composite and efficiently enhanced the HER performance. Notably, the overpotential was merely 96 mV at 10 mA·cm−2 current density, and the Tafel slope was only 48.9 mV·dec−1. Moreover, CGO36@CC displayed remarkable catalytic activity and sustained HER catalytic stability. The theoretical catalytic prowess of CGO36@CC stemmed from the collaborative influence of germanium and cobalt atoms within the exposed 111 crystal plane of the Co2GeO4 molecular framework. The amalgamation of Co2GeO4 with carbon cloth fiber conferred upon the composite electrocatalyst both superior theoretical catalytic activity and enhanced electron transfer capability. This work provides a novel strategy for exploring a highly efficient composite electrocatalyst combined transition metal with carbon material to accelerate the HER activity.

Hierarchical Superhydrophilic/Superaerophobic Ni3S2/VS2 Nanorod-Based Bifunctional Electrocatalyst Supported on Nickel Foam for Overall Urea Electrolysis.

The design and preparation of effective nonprecious metal-based catalysts for the urea oxidation reaction (UOR) coupled with the hydrogen evolution reaction (HER) are of great significance to solve both energy shortage and environmental pollution problems. In this study, a novel hierarchical superhydrophilic and superaerophobicity three-dimensional nanorod-like bifunctional catalyst with a heterostructure (Ni3S2/VS2) was prepared on nickel foam via a simple one-step hydrothermal method, serving as an excellent electrocatalyst for both UOR and HER. The formed heterostructure significantly alters the electronic structure, optimizing charge transfer and increasing the number of active sites, which enhances the electrocatalytic performance of Ni3S2/VS2. As a result, this catalyst requires an extremely low potential of 1.396 V at the current density of 100 mA cm-2 for UOR and only 164 mV overpotential at -10 mA cm-2 for HER. Notably, a constructed two-electrode electrolyzer system (Ni3S2/VS2∥Ni3S2/VS2) demonstrates extraordinary activity and long-term stability, achieving a current density of 10 mA cm-2 at a low cell voltage of 1.48 V, which is superior to majority of the reported catalysts. This work demonstrates that the formation of heterostructures can effectively enhance the catalytic activity of nanomaterials toward UOR and HER and provides a feasible strategy for fabricating highly efficient nonprecious metal overall urea electrocatalysts.

Modulated electronic structure of atomic W-doped NiO/Cr2S3 nanotube heterostructure on nickel foam for enhanced overall water splitting

Critical for advancing hydrogen energy industrialization is the need to engineer durable and highly active non-precious electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER). In this study, we developed a novel approach to construct a vertically grown W-doped NiO/Cr2S3 nanotube heterostructure on nickel foam (referred to as tube W-NiO/Cr2S3/NF). This heterostructure serves as an efficient and bifunctional electrocatalyst for overall water splitting through a combination of electrodeposition and etching processes. Our systematic investigations revealed that W-doping effectively induces modifications in the electronic structure of NiO/Cr2S3, thereby boosting its intrinsic activities. Density functional theory reveals that catalytic activity for HER is influenced by the energy states of active valence dz2 orbitals. After W-doping, the resulting antibonding state orbital's unique property, neither completely empty nor fully filled, leads to an ideal hydrogen adsorption energy. Consequently, tube W-NiO/Cr2S3/NF exhibits significantly enhanced performance for overall water splitting. As a bifunctional electrode, tube W-NiO/Cr2S3/NF demonstrates remarkable activity, achieving a cell voltage of 1.58 V at a current density of 10 mA cm−2 for overall water splitting. Furthermore, it exhibits outstanding stability over 100 h in a 1.0 M KOH solution, outperforming commercial Pt-C and IrO2 counterparts.

Laser-Induced Vertical Graphene Nanosheets for Electrocatalytic Hydrogen Evolution.

Efficient and affordable electrocatalysts are fundamental for the sustainable production of hydrogen from water electrolysis. Here, an approach for the rapid production of laser-induced vertical graphene nanosheets (LIVGNs) through the exfoliation of the graphite foil under laser irradiation is presented. The density of the formed LIVGNs is ∼3 per 100 μm2. On leveraging the inherent flexibility and conductivity of the graphite foil substrate, the resulting LIVGNs exhibit a 2.2-fold increase in capacitance, making them promising candidates for electrode applications. The laser-induced surface reconstruction introduces abundant sharp edges to the LIVGNs, enhancing their electrocatalytic potential for hydrogen evolution. In electrocatalytic hydrogen evolution tests in acidic media, the LIVGNs demonstrate superior performance with a remarkable decrease in the required overpotential at 10 mA cm-2, from -555 mV for the pristine graphite foil to -348 mV for LIVGNs. This improvement is attributed to the active sites provided by the sharp edges, facilitating hydrogen species adsorption. Furthermore, the hydrophilic behavior of LIVGNs is enhanced through the anchoring of oxygen-containing groups, promoting the rapid release of the produced hydrogen bubbles. Importantly, the modified LIVGN electrode exhibits long-term stability across a wide range of current densities during chronoamperometry tests. This research introduces a transformative strategy for the efficient preparation of vertical graphene sheets on conductive graphite foils, showcasing their potential applications in electrocatalysis and energy storage.

High-throughput screening of efficient graphdiyne supported transition metal single atom toward water electrolysis and oxygen reduction

Efficient single-atom electrocatalysts show great potential for application in the field of renewable energy. In this work, dispersion-corrected density functional theory (DFT) calculations based on high-throughput screening were used to identify effective graphdiyne (GDY) supported single-atom electrocatalysts (SAECs) for water electrolysis and the oxygen reduction reaction (ORR). The solvation effect on the electrocatalytic performance of the catalysts was carefully discussed. A general design principle was established to evaluate the activities of TM@GDY SAECs for ORR and oxygen evolution reaction (OER). ΔGOH* could serve as the sole descriptor for the onset potential of OER and ORR. Additionally, a universal structural descriptor φ, which is strongly related to ΔGOH*, was identified. This descriptor only includes intrinsic features such as the number of electrons in d orbitals and elemental electronegativity. Consequently, a structure-activity volcano was plotted. Combined with the electronic properties calculations, the mechanism behind the relationship between ΔGOH* and descriptor φ was deeply analyzed. Among the investigated candidates, TM@GDY (TM = Ni, Pt, Pd, Cu, Co, Rh, and Ag) are potential bifunctional electrocatalysts for OER and ORR. Three non-noble metal-based SAECs (Ni@GDY, Co@GDY, and Cu@GDY) and two noble metal-based SAECs (Rh@GDY and Ag@GDY) are potential trifunctional electrocatalysts for OER, ORR, and the hydrogen evolution reaction.

Boosting the Production of Hydrogen from an Overall Urea Splitting Reaction Using a Tri-Functional Scandium-Cobalt Electrocatalyst.

The creation of highly efficient and economical electrocatalysts is essential to the massive electrolysis of water to produce clean energy. The ability to use urea reaction of oxidation (UOR) in place of the oxygen/hydrogen evolution process (OER/HER) during water splitting is a significant step toward the production of high-purity hydrogen with less energy usage. Empirical evidence suggests that the UOR process consists of two stages. First, the metal sites undergo an electrochemical pre-oxidation reaction, and then the urea molecules on the high-valence metal sites are chemically oxidized. Here, the use of scandium-doped CoTe supported on carbon nanotubes called Sc@CoTe/CNT is reported and CoTe/CNT as a composite to efficiently promote hydrogen generation from highly durable and active electrocatalysts for the OER/UOR/HER in urea and alkali solutions. Electrochemical impedance spectroscopy indicates that the UOR facilitates charge transfer across the interface. Furthermore, the Sc@CoTe/CNT nanocatalyst has high performance in KOH and KOH-containing urea solutions as demonstrated by the HER, OER, and UOR (215mV, 1.59, and 1.31V, respectively, at 10mA cm-2 in 1m KOH) and CoTe/CNT shows 195 mV, 1.61 and 1.3V, respectively. Consequently, the total urea splitting system achieves 1.29V, whereas the overall water splitting device obtaines 1.49V of Sc@CoTe/CNT and CoTe/CNT shows 1.54, 1.48 V, respectively. This work presents a viable method of combining HER with UOR for maximally effective hydrogen production.

Construction of a Three-Phase MnS2/Co4S3/Ni3S2 Heterostructure for Boosting Oxygen Evolution.

The rational construction of highly efficient electrocatalysts for the oxygen evolution reaction (OER) plays a critical role in energy conversion systems. Designing heterostructures is a common and effective strategy to improve the performance of electrocatalysts. In this paper, an MnS2/Co4S3/Ni3S2 heterostructure was synthesized on Ni foam using a one-step vulcanization method. It provides a modified electronic structure and plentiful three-phase heterogeneous interfaces that can effectively enrich the active sites and accelerate electron transfer, thereby improving the OER activity. Thanks to the heterostructure, the MnS2/Co4S3/Ni3S2 exhibits a low overpotential of 265 and 304 mV for the OER to reach current densities of 50 and 100 mA/cm2, respectively. Furthermore, the surface reconstruction of MnS2/Co4S3/Ni3S2 has been investigated, which revealed the formation of metal hydr(oxy)oxides evolved during the OER process. This work provides a facile strategy for constructing three-phase heterostructures, shedding light on the development of high-performance, nonprecious metal-based OER electrocatalysts.

In-Situ Construction of Fe-Doped NiOOH on the 3D Ni(OH)2 Hierarchical Nanosheet Array for Efficient Electrocatalytic Oxygen Evolution Reaction.

Accessible and superior electrocatalysts to overcome the sluggish oxygen evolution reaction (OER) are pivotal for sustainable and low-cost hydrogen production through electrocatalytic water splitting. The iron and nickel oxohydroxide complexes are regarded as the most promising OER electrocatalyst attributed to their inexpensive costs, easy preparation, and robust stability. In particular, the Fe-doped NiOOH is widely deemed to be superior constituents for OER in an alkaline environment. However, the facile construction of robust Fe-doped NiOOH electrocatalysts is still a great challenge. Herein, we report the facile construction of Fe-doped NiOOH on Ni(OH)2 hierarchical nanosheet arrays grown on nickel foam (FeNi@NiA) as efficient OER electrocatalysts through a facile in-situ electrochemical activation of FeNi-based Prussian blue analogues (PBA) derived from Ni(OH)2. The resultant FeNi@NiA heterostructure shows high intrinsic activity for OER due to the modulation of the overall electronic energy state and the electrical conductivity. Importantly, the electrochemical measurement revealed that FeNi@NiA exhibits a low overpotential of 240 mV at 10 mA/cm2 with a small Tafel slope of 62 mV dec-1 in 1.0 M KOH, outperforming the commercial RuO2 electrocatalysts for OER.

Unraveling the Potential Dependence of Active Structures and Reaction Mechanism of Ni‐based MOFs Electrocatalysts for Alkaline OER

AbstractNickel‐based metal‐organic frameworks (MOFs) with flexible structure units provide a broad platform for designing highly efficient electrocatalysts, especially for alkaline oxygen evolution reaction (OER). However, the stability of MOFs under harsh and dynamic reaction conditions poses significant challenges, resulting in ambiguous structure‐activity relationships in MOFs‐based OER research. Herein, Ni‐benzenedicarboxylic acid‐based MOF (NiBDC) is selected as prototypical catalyst to elucidate its real active sites for OER and reaction pathway under different reaction states. Electrochemical measurements combined with X‐ray absorption spectroscopy (XAS) and Raman spectroscopy reveal that the complete reconstruction of NiBDC to β‐NiOOH in the chronoamperometry activation process is responsible for significantly increased OER performance. In situ XAS and Raman results further demonstrate the electro‐oxidation of β‐NiOOH into γ‐NiOOH at high‐potential state (above 1.6 V vs RHE). Furthermore, the collective evidences from key reaction intermediates and isotope‐labeled products definitely unravel the potential dependence of OER mechanism: OER process at low‐potential state proceeds mainly through the lattice oxygen‐mediated mechanism, while adsorbate evolution mechanism emerges as the predominant pathway at high‐potential state. Interestingly, the dynamically changing OER mechanism can not only reduce the required overpotential at the low‐potential state but also improve the electrochemical stability of catalysts at high‐potential state.

Doped‐Sn Enhanced the Performance of BiOCl Nanosheet on Electrocatalytic Synthesis of Hydrogen Peroxide

AbstractThe hydrogen peroxide (H2O2) produced through electrochemical two‐electron oxygen reduction reaction (2e− ORR) is a promising green synthesis method and served as potential strategy to replace the energy‐intensive anthraquinone process. Nevertheless, the design of low‐cost and efficient electrocatalysts for 2e− ORR remains a formidable challenge. In this study, Sn‐BiOCl nanosheets electrocatalysts are prepared for expediting the 2e− ORR, achieving a high H2O2 selectivity of 92.9%, and the H2O2 yield of 10628 mg L−1 h−1 (0.1 mg cm−2) in a flow‐cell device. The in situ ATR‐SEIRAS results reveal that Sn‐BiOCl enhances the adsorption and activation of *OOH compared to BiOCl, resulting in higher activity and selectivity for 2e− ORR. Furthermore, this study investigates the potential for on‐site production and application of H2O2 using Sn‐BiOCl, which displays a 95% degradation removal of dyes (RhB, MB, and MO) within 20 min. This work not only have an insight into the critical roles of Bi and Sn atoms in enhancing the catalytic performance but also provides a thought to design efficient catalysts for production H2O2 via electrochemical 2e− ORR.

Zinc Vaporization Induced Formation of Desired Ni Nanoparticles Coated with Ultrathin Carbon Shells for Efficient Electrocatalytic H2 Production Coupling with Methanol Upgrading.

The integration of the hydrogen evolution reaction (HER) with the methanol oxidation reaction (MOR) has been demonstrated to be a viable strategy for the energy-saving generation of H2 and value-added formate, which relies primarily on highly active and cost-effective bifunctional electrocatalysts. Herein, an efficient electrocatalyst consisting of controllable Ni nanoparticles (NPs) coated with ultrathin graphitic carbon shells was obtained by the pyrolysis of a Ni-Zn metal-organic framework. Intriguingly, we found that zinc vaporization not only resulted in the relatively small Ni NPs but also ultrathin carbon shells (≤3 layers). The density functional theory simulations confirmed that these ultrathin carbon shells significantly influenced electrocatalytic activity by facilitating electron transfer from the Ni core to the carbon shell. The optimized Ni1(Zn)@C demonstrated high catalytic activity for both HER and MOR, and only a low potential of 97 mV at 10 mA cm-2 was required for HER and 1.48 V at 30 mA cm-2 for MOR. In a two-electrode electrocatalytic cell measurement, a cell voltage of 1.63 V was observed at 10 mA cm-2 in the presence of methanol, 240 mV lower than that without methanol.

RhCo alloyed nanodendrites as an efficient electrocatalyst for boosting electro oxidation of ethylene glycol in alkaline media

Since Pt- and Pd-based catalysts, as the most common anode catalysts, usually suffer from CO poisoning issue during the electro oxidation of ethylene glycol, it is essential to explore more high-efficiency Pt- and Pd-free ethylene glycol oxidation reaction (EGOR) catalysts for better service in direct ethylene glycol fuel cells (DEGFCs). In this work, RhCo alloyed nanodendritic catalysts applied on EGOR in alkaline solution are designed and synthesized by a solvothermal method. The RhCo nanodendrites consist of radially distributed pine tree shaped flakes and rod-like crystals. The mass activity for the as-prepared Rh3Co1 nanodendrites during the EGOR reaches up to 3018.7 mA mg−1, which is 2.2-folds higher than that of commercial Pt/C. Moreover, the Rh3Co1 nanodendrites exhibit better stability and CO tolerance toward the EGOR than pure Rh nanodendrites and commercial Pt/C. Experimental observations in combination with density functional theory (DFT) calculations reveal that the notably promoted catalytic performances of Rh3Co1 nanodendrites are mainly attributed to the distinct nanodendritic morphology and the synergistic effect of Rh and Co. This work provides a valuable insight for developing efficient electrocatalysts for DEGFCs.

Activation of stannic oxide by the incorporation of ruthenium oxide nanoparticles for efficient hydrogen evolution reaction

The demand for clean energy has been increasing rapidly in recent years, and hydrogen is one of the most promising fuels due to its high energy density and clean combustion. The hydrogen evolution reaction (HER) is a key process for hydrogen production, and developing efficient electrocatalysts is essential for HER. While this research is of great interest, it is still challenging to select an ideal material for electrochemical HER in an acidic condition. In this article, SnO2 is activated through the incorporation of a small amount of ruthenium oxide nanoparticles, serving as an auspicious catalyst characterized by exceptional catalytic stability in an acidic medium, outstanding charge transport ability, and abundance of active sites. Herein, the RuO2-SnO2 nanocomposite is synthesized through the precipitation method and characterized using XRD, XPS, TEM, EDX, and BET techniques. The electrochemical results show that the nanocomposite of 0.5 wt% RuO2/SnO2 has excellent electrocatalytic activity for HER, as evidenced by lower charge transfer resistance (0.08 kΩ), low onset potential (−0.02 V), and high Faradaic efficiency (97 %). It demonstrates a substantially reduced overpotential of 237 mV to reach a current density of 10 mA cm−2, alongside a minimal Tafel slope of 117 mV dec−1. The findings of the research will provide a promising strategy to design and synthesize high-performing catalysts for HER.

A high-throughput screening of catalyst for efficient nitrogen fixation: Transition metal single-atom anchored on an emerging synthesized biphenyl network

Synthesizing efficient and selective green ideal catalysts has been an increasingly critical, yet unsolved, issue for the ammonia synthesis industry, hindering the growing global demand for environmental protection and energy efficiency. Electrocatalytic nitrogen reduction reaction (eNRR) is a promising technology for low-energy ammonia synthesis. However, designing efficient electrocatalysts for NRR remains challenging. The emergence of graphene-like substrates offers exciting prospects for addressing this challenge and facilitating single-atom catalysts in eNRR. Here, we report the innovative selection of a recently synthesized two-dimensional biphenyl network (2D BPN) compound as a substrate. Its excellent conductivity and porosity enable stable transition metal atoms (TMs) support for constructing eNRR electrocatalysts. we evaluated the feasibility of 23 TMs anchored on BPN for eNRR by high-throughput first-principles calculations. Through a systematic five-step strategy, we identified several single-atom catalysts (SACs) with potential for eNRR, including Mo@BPN, V@BPN, W@BPN, and Re@BPN. Among them, Mo@BPN exhibited the best balance in the adsorption of key reaction intermediates (e.g., N2H and NH3) and demonstrated a low limiting potential (-0.37 V). In addition, the underlying mechanism of NRR activity was elucidated by analyzing the extrinsic patterns revealed through the screened catalysts. A triangular volcano diagram, incorporating the initial protonation step, adsorption free energy, and final protonation step, revealed the NRR activity trend. Overall, this study provides a solid theoretical foundation and valuable guidance for future experimental exploration of efficient electrocatalysts for ammonia synthesis on BPN. Crucial insights into the theoretical design of efficient electrocatalysts are also offered.

Stabilization of Cu2O catalyst via strong electronic interaction for selective electrocatalytic CO2 reduction to ethanol

While cuprous oxide (Cu2O) remains the most efficient and viable electrocatalyst for the electrochemical conversion of CO2 to ethanol, its reduction to Cu during the catalytic CO2RR process poses a barrier to its industrial application. To address this challenge, we have reported a highly stable Cu2O-based catalyst by introducing pseudo-capacitive NiCo2O4 intermediate layers. The current densities observed on the surface of the prepared NF@NiCo2O4@Cu2O remained consistent over a 15-hour stability test, demonstrating excellent durability that exceeds that of the NF@Cu2O electrode by more than 200 %. Experimental characterization and DFT analysis indicate that the exceptional stability is primarily attributed to the pseudo-capacitive NiCo2O4 interlayer with cyclic charge–discharge properties, where NiCo2O4 can capture and eliminate accumulated reduced electrons around Cu2O under strong electronic interactions and release electrons through catalytic reduction to produce hydrogen. Furthermore, the NiCo2O4@Cu2O (111) heterostructure significantly reduces the Gibbs free energy (ΔG) required for C-C coupling of *CO intermediates compared to Cu2O (111). This mechanism establishes a cyclic charge–discharge process in order to prevent reduction of Cu2O into copper monomers. As a result, NF@NiCo2O4@Cu2O demonstrates a C2H5OH faradaic efficiency of 56.9 % at −0.5 V vs. RHE, surpassing many other Cu-based catalytic electrodes. This work provides new insights into studying strong electronic interaction structures to eliminate electron enrichment at the catalytic site for stabilizing catalysts and also offers an effective strategy for designing catalysts that maintain long-term stability in industrial applications.

Integrating NiSe2-MoSe2 heterojunctions with N-doped porous carbon substrate architecture for an enhanced electrocatalytic water splitting device

The development of sustainable energy technologies relies on the exploitation of efficient and durable electrocatalysts for water splitting at high current densities. Our work presents a novel bifunctional catalyst, denoted as NM@NC/CC, which combines the benefits of NiSe2-MoSe2 heterojunctions with nitrogen-enriched porous carbon derived from metal-organic frameworks (MOFs). The integration of these components is designed to harness their combined advantages, which include enhanced electron transfer, improved mass and gas evolution dynamics, and an increased number of catalytically active sites. These features collectively optimize the energetics for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, the catalyst facilitates rapid kinetics for the overall water-splitting process. The NM@NC/CC demonstrates low overpotentials, requiring only 91 mV for the HER and 280 mV for the OER to reach a current density of 10 mA cm−2. Even at higher current densities of 100 mA cm−2 for HER and 50 mA cm−2 for OER, the overpotentials are only 159 mV and 350 mV, respectively. Additionally, a two-electrode setup using this catalyst achieves a current density of 10 mA cm−2 with a minimal cell voltage of 1.56 V. The insights gained from this study will contribute to the advancement of electrocatalysts for energy conversion technologies.

Tuning the local electronic structure of Co15V-ZIF through bimetallic synergies as a bifunctional electrocatalyst for overall water splitting

Co-based bimetallic zeolite imidazolate frameworks (ZIFs) have been shown as promising electrocatalysts for the oxygen evolution reaction, but their electronic structure’s influence on the catalytic performance for overall water splitting still needs further investigation. In this study, Co15V-ZIF, structured as two-dimensional (2D) nanosheet arrays, are grown on nickel foam using one-step co-precipitation strategy. Owing to the synergistic effects of vanadium (V) and cobalt (Co) reasonably regulating the electronic structure, the synthesized bimetallic ZIFs demonstrate superior catalytic performance, which required the overpotentials of only 227 and 68 mV to achieve a current density of 10 mA cm−2 in 1 M KOH for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Furthermore, the water electrolyzer assembled with bimetallic ZIF as cathode and anode exhibits the capability to achieve 10 mA cm−2 at a low cell voltage of 1.57 V. In situ Raman spectroscopy reveals that the introduction of V facilitates the formation of V-CoOOH, the real active site for OER, at lower applied potentials. Besides, it induces a local acidic environment on V-Co(OH)2, the real active sites, thereby enhancing the HER performance of the sample. Density Functional Theory (DFT) calculations further show that the synergistic effects of V and Co induce electron redistribution, thereby improving electrical conductivity, reducing the energy barrier for water dissociation and hydrogen adsorption, which promotes the formation of H3O+ and triggering H3O+-induced water reduction in alkaline media. This work provides new insight into tailoring electronic structures to rationally design highly efficient ZIF electrocatalysts.

Boosting the activity of nitrogen-doped carbon catalyst by the guided formation of active sites and enhanced scavenging on reactive oxygen species under the regulation of cerium

The design of nitrogen-doped carbon materials with high density of active sites is of paramount importance for catalysis of the oxygen reduction reaction (ORR). Herein, an efficient oxygen reduction electrocatalyst (CL-Fe/(Fe,Ce)xOy-NC) is developed by planting carbon nanotubes with encapsulated Fe/(Fe,Ce)xOy particles on porous carbon polyhedron particles derived from calcinated ZIF-8 framework. The introduction of Ce evidently promotes the formation of pyridinic nitrogen, graphitic nitrogen and metal nitrogen species in carbon matrix, enhancing the catalytic activity towards the ORR. The Ce oxide in the catalyst effectively scavenges the active oxygen species in ORR process. Under the synergistic effect of high specific surface area with Ce species, the CL-Fe/(Fe,Ce)xOy-NC has a better half-wave potential (0.861 V vs. RHE), faster kinetics (44.13 mV dec−1) and is more stable than the commercial Pt/C catalyst. The zinc-air battery assembled with CL-Fe/(Fe,Ce)xOy-NC has the highest power density of 195 mW cm−2, energy density of 858 Wh kg−1, and better durability. This work presents a novel approach to enhance the efficacy of nitrogen-doped carbon-based catalysts, paving a possible way to substitute the precious platinum catalysts for a variety of electrochemical energy devices.

Manganese doped tailored cobalt sulfide as an accelerated catalyst for oxygen evolution reaction

Developing an efficient, robust, and noble metal-free electrocatalyst that can catalyse oxygen evolution reactions (OER) remains a significant challenge. CoS2, a representative of pyrite form transition metal dichalcogenides, has recently been identified as an economical catalyst. Here, an incredibly quick and scalable technique for novel catalysts synthesized with the use of the microwave method was introduced. Manganese-doped cobalt sulphide (Mn-CoS2) showed outstanding OER with a very low overpotential of 227 mV at 10 mA cm−2. Exposure of surface atoms resulted in high electrochemical activity, where the defects facilitated charge and mass transfer along the nanostructure, allowing surface dependent electrochemical reactions to be performed more efficiently. The electronic properties of pristine and transition-metal-doped CoS2 structures were also investigated using density functional theory (DFT). To better understand transition metal’s dependent impact on crystal structure, orbital electronic participation, charge density, and charge transformation in both pristine and Mn-dopedCoS2 frameworks were calculated and analysized. Our synthesis approach is primarily commercial and extensible, overcoming synthesis challenge of transition metal sulphide nanostructures with prime quality and implying a potential for commercial uses.