Interfacial engineering of CoP/CoS2 heterostructure for efficiently electrocatalytic pH-universal hydrogen production

Redox-mediated oxygen evolution reaction: Engineering oxygen vacancies and heterojunctions in CeFeCo-UiO-66/layered double hydroxide via a two-step corrosion strategy

Modifying metal-organic frameworks (MOFs)-based electrocatalysts remains crucial for enhancing oxygen evolution reaction (OER) performance. Although oxygen vacancies (VO) are recognized as important for OER, their concentration control and relationship with catalytic activity remain unclear. In this study, we employ the redox potential difference between Co2+/3+ (0.55 eV) and Ce3+/4+ (1.44 eV) to induce corrosion on iron foam (IF), driving the redox reaction Ce4+ + Co2+ → Ce3+ + Co3+ to generate VO. The VO content can be qualitatively controlled by adjusting corrosion time, as verified by electron paramagnetic resonance (EPR). The CeFeCo-UiO-66/LDH catalyst delivers exceptional catalytic activity (overpotential η = 273 ± 3 mV @ 100 mA cm-2). Combined X-ray photoelectron spectroscopy (XPS), EPR, in-situ Raman, and Density functional theory (DFT) analyses reveal that the redox interaction between Ce and Co generates VO. These VO species facilitate the formation of active CoOOH during the OER. This work offers insights for designing VO engineering strategies in electrocatalytic systems.

Ce-doped NiCoP/ Co3O4 composite Nanostructures on Ni foam and their enhanced performance for water and urea electrolysis

Producing hydrogen through freshwater or urea-containing wastewater electrolysis using renewable electricity requires multifunctional catalysts made from nonprecious metals. In the current study, we disclose the rational fabrication of oxide/phosphide heterostructure nanorods with rare earth metal doping on nickel foam (NF), denoted Ce-NiCoP/Co3O4/NF, via partial phosphorization. Benefiting from intrinsic interface formation and doping effects, the interaction between the coupling components facilitates electron transfer, optimizing the electronic configuration of the Ce-NiCoP/Co3O4/NF catalyst. Ce-NiCoP/Co3O4/NF exhibited a competitive potential of - 0.151 V for hydrogen evolution reaction, 1.50 V for oxygen evolution reaction (OER), and 1.33 V (versus reversible hydrogen electrode) toward urea oxidation reactions (UOR) at 100 mA cm-2. In situ Fourier-transform infrared combined with electrochemical analysis detects *OOH and *O2- intermediates in OER, as well as CO32- and CNO- ions, alongside the N-H vibration in UOR, providing deeper insight into the OER and UOR mechanisms on the Ce-NiCoP/Co3O4/NF. More importantly, the catalyst exhibited an activity of 20 mA cm-2 requiring voltages as low as 1.52 V for unassisted water splitting and 1.27 V for urea-assisted electrolysis.

Rapid charge transfer and enhanced internal electric field in core-shell Schottky junction for photocatalyzed Fenton reaction: Performance and mechanism

The challenge of achieving fast and efficient separation of photogenerated carriers lies in the kinetics of photocatalytic reactions. In the present study, we employed solvothermal and surfactant-induced methods to uniformly grow BiOCl on the surface of CoS Nano-flower balls, thereby forming core-shell Schottky heterojunctions. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations demonstrated the directional transfer of electrons and the establishment of an enhanced built-in electric field during the formation of these heterojunctions. This rapid separation of photogenerated carriers effectively activates the photo-Fenton system and enhances its synergistic effect. After 60 min of light exposure and the addition of Peroxymonosulfate (PMS), 100C-PBOC effectively degraded 95.6 % of ciprofloxacin, exhibiting a degradation rate k-value that is 1.97 times higher than that of photocatalytic degradation alone. Considering the insufficiency of mineralization, we conducted liquid chromatography-mass spectrometry (LC-MS) tests in conjunction with DFT calculations to elucidate the complete degradation mechanism and assess the toxicity of the degraded intermediates, most of which exhibited significantly reduced toxicity. This study addresses the gap in the application of CoS co-catalysts in photocatalytic wastewater treatment and offers a novel approach to the design of core-shell heterojunctions.

Phase regulation of Ni(OH)2 nanosheets induced by W doping as self-supporting electrodes for boosted water electrolysis

Developing high-performance and low-cost electrodes for hydrogen and oxygen evolution reactions (HER and OER, respectively) represents a pivotal challenge in the field of water electrolysis. Herein, W doped NiFe LDH nanosheets (NiFe-Wx/NF) were immobilized on nickel foam (NF) through one-step corrosion engineering, which induced the coexistence of α-Ni(OH)2 and β-Ni(OH)2. The doping of large atomic radius W influenced the growth of crystal planes of Ni(OH)2, promoting the formation of α-Ni(OH)2, which results in large layer spaces and neatly arranged nanosheets structure. The optimized NiFe-W0.5/NF catalyst require potentials of only 69 to attain 10 mA/cm2 for HER, and require overpotentials of 269 mV to reach 100 mA/cm2 current density for OER, respectively. The W6+ with high oxidation state can withdraw neighboring electrons from Ni, altering the adsorption energy of hydrogen intermediates, which improves the Volmer step and electrical conductivity in HER. And the large layer space of α-Ni(OH)2 in NiFe-W0.5/NF can be contributed to accelerating the formation of high valence γ-NiOOH, which can accelerate OER kinetics. In addition, the NiFe-W0.5/NF catalyst also provides an overall water splitting activity of 780 mA/cm2 current density at a cell voltage of only 1.90 V, and remains highly stable for over 70 h at 100 mA/cm2, which makes it a bifunctional efficient catalyst for water electrolysis.

Synergistic high-entropy phosphides with phosphorus vacancies as robust bifunctional catalysts for efficient water splitting

High-entropy phosphides (HEPs) have garnered increasing interest as innovative electrocatalysts for water splitting, highlighted by their distinctive catalytic activity, elemental synergy, and tunable electronic configuration. Herein, a novel electrode comprising CoNiCuZnFeP nanocubes with rich phosphorus vacancies was fabricated through coprecipitation and phosphorization two-step method. The synergistic interaction among metal elements and the modulation of the electronic configuration by phosphorus vacancies augmentation enhance the catalytic performance for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The CoNiCuZnFeP catalyst demonstrates overpotentials of 318 mV for HER and 204 mV for OER at 100 mA cm-2, while maintaining a remarkable durability exceeding 700 h. The catalyst, as the dual-electrode for water electrolysis, requires a voltage of 1.74 V to attain 100 mA cm-2. Theoretical calculations reveal that the combination of high entropy and phosphorus vacancies can effectively regulate the local charge distribution and electronic characteristics of phosphides, leading to the optimization of adsorption energies and the reduction of the potential energy barrier for water decomposition. This study provides an attractive OER electrocatalyst for renewable hydrogen via efficient water splitting, and paves the way for the design of efficient and stable electrocatalysts with high-entropy materials.

Catalytic synergism in heterostructural Ta-doped Mo-Ni-S nanospheres: an efficient bifunctional catalyst for water splitting

Designing suitable and efficient electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for sustainable hydrogen production. To date, extensive studies have focused on transition metal chalcogenides (TMSs) due to their unique electronic structure and strong ability to be modified. Herein, we reported a Ta-doped MoS2/NiS catalyst supported on NF with a stable hierarchical nanosphere structure (Ta-MNS). The synergy between the MoS2 and NiS phases in the same plane enhanced the mechanical strength and exposed more active sites, while Ta5+ was applied to adjust the electronic structure, resulting in a well-dispersed and flexible morphology. Moreover, the formation of the -S-Ta5+-S- bridge was proposed as a significant factor in enhancing the link between components at the active phase and further promoting electron transfer. As a result, for HER, the synthesized Ta-MNS required overpotentials of only 35 and 127 mV at current densities of 10 and 100 mA cm-2, respectively. Furthermore, it demonstrated outstanding performance for OER and excellent stability, maintaining stable operation for more than 80 h. This paves a new avenue for the design of novel catalysts for water splitting.

Transition Metal Anchored Novel Holey Boron Nitride Analogues as Single-Atom Catalysts for the Hydrogen Evolution Reaction

The increasing global energy demand and environmental pollution necessitate the development of alternative, sustainable energy sources. Hydrogen production through electrochemical methods offers a carbon-free energy solution. In this study, we have designed novel boron nitride analogues (BNyne) and investigated their stability and electronic properties. Furthermore, the incorporation of transition metals (TM) at holey sites in these analogues was explored, revealing their potential as promising electrocatalysts for the hydrogen evolution reaction (HER). The inclusion of transition metals significantly enhances their structural stability and electronic properties. The TM-anchored BNynes exhibit optimal Gibbs free energy changes (ΔGH) for effective HER performance. Additionally, the favorable alignment of d-band centers near the Fermi level supports efficient hydrogen adsorption. Machine learning models, particularly the Random Forest model, have also been employed to predict ΔGH values with high accuracy, capturing the complex relationships between material properties and HER efficiency. This dual approach underscores the importance of integrating advanced computational techniques with material design to accelerate the discovery of effective HER catalysts. Our findings highlight the potential of these tailored boron nitride analogues to enhance electrocatalytic applications and improve HER efficiency.

Highly dispersed Ir nanoparticles on Ti3C2Tx MXene nanosheets for efficient oxygen evolution in acidic media

The industrialization of hydrogen production technology through polymer electrolyte membrane water splitting faces challenges due to high iridium (Ir) loading on the anode catalyst layer. While rational design of oxygen evolution reaction (OER) electrocatalysts aimed at effective iridium utilization is promising, it remains a challenging task. Herein, we present exfoliated Ti3C2Tx MXene as a highly conductive and corrosion-resistant support for acidic OER. We develop an alcohol reduction method to achieve uniform and dense loading of ultrafine Ir nanoparticles on the MXene surface. The IrO2/TiOx heterointerface is formed in situ on the Ir@Ti3C2Tx MXene surface, acting as a catalytically active phase for OER during electrocatalysis. The electron interactions at the IrO2/TiOx heterointerface create electron-rich Ir sites, which reduce the adsorption properties of oxygen intermediates and enhance intrinsic OER activity. Consequently, the prepared Ir@Ti3C2Tx exhibits a mass activity that is 7 times greater than that of the benchmark IrO2 catalyst for OER in acidic media. In addition, the /Ti3C2Tx MXene support can stabilize the Ir nanoparticles, so that the stability number of Ir@Ti3C2Tx MXene is about 2.4 times higher than that of the IrO2 catalyst.

Vacancy-rich heterogeneous MnCo2O4.5@NiS electrocatalyst for highly efficient overall water splitting

Alkaline water electrolysis is regarded as a promising technology for sustainable energy conversion. Spinel oxides have attracted considerable attention as potential catalysts because of their diverse metal valence states. However, achieving the required current densities at low voltages is a challenge due to its limited active sites and suboptimal electron transport. In this study, we present a novel bifunctional catalyst composed of MnCo2O4.5 nanoneedles grown on NiS nanosheets for water electrolysis. Remarkably, MnCo2O4.5@NiS demonstrates exceptional catalytic activity, requiring 187 and 288 mV to achieve a current density of 100 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The impressive performance of MnCo2O4.5@NiS is demonstrated by the lower value of voltage 1.44 V needed to deliver the current density of 10 mA cm-2, which outperformed the 1.66 V required for a commercial Pt/C||RuO2 system. Detailed structure analysis and density functional theory (DFT) calculations reveal that the MnCo2O4.5@NiS heterostructure enhances electron transfer at the interface, promotes the formation of oxygen vacancies and tunes the electronic structures of Mn and Co. These findings underscore the potential of MnCo2O4.5@NiS as an efficient and cost-effective electrocatalyst for hydrogen production.

Nanocrystalline transition metal tetraborides as efficient electrocatalysts for hydrogen evolution reaction at the large current density

While great efforts have been made to improve the electrocatalytic activity of existing materials toward hydrogen evolution reaction (HER), it is also importance for searching new type of nonprecious HER catalysts to realize the practical hydrogen evolution. Herein, we firstly report nanocrystalline transition metal tetraborides (TMB4, TM=W and Mo) as an efficient HER electrocatalyst has been synthesized by a single-step solid-state reaction. The optimized nanocrystalline WB4 exhibits an overpotential as low as 172 mV at 10 mA/cm2 and small Tafel slope of 63 mV/dec in 0.5 M H2SO4. Moreover, the nanocrystalline WB4 outperforms the commercial Pt/C at high current density region, confirming potential applications in industrially electrochemical water splitting. Theoretical study reveals that high intrinsic HER activity of WB4 is originated from its large work function that contributes to the weak hydrogen-adsorption energy. Therefore, this work provides new insights for development of robust nanocrystalline electrocatalysts for efficient HER.

Pt Single Atom-Doped Triphasic VP-Ni3P-MoP Heterostructure: Unveiling a Breakthrough Electrocatalyst for Efficient Water Splitting

Enhancement of an alkaline water splitting reaction in Pt-based single-atom catalysts (SACs) relies on effective metal-support interactions. A Pt single atom (PtSA)-immobilized three-phased PtSA@VP-Ni3P-MoP heterostructure on nickel foam is presented, demonstrating high catalytic performance. The existence of PtSA on triphasic metal phosphides gives an outstanding performance toward overall water splitting. The PtSA@VP-Ni3P-MoP performs a low overpotential of 28 and 261 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a current density of 10 and 25 mA cm-2, respectively. The PtSA@VP-Ni3P-MoP (+,-) alkaline electrolyzer achieves a minimum cell voltage of 1.48 V at a current density of 10 mA cm-2 for overall water splitting. Additionally, the electrocatalyst exhibits a substantial Faradaic yield of ≈98.12% for H2 and 98.47% for O2 at a current density of 50 mA cm-2. Consequently, this study establishes a connection for understanding the active role of single metal atoms in substrate configuration for catalytic performance. It also facilitates the successful synthesis of SACs, with a substantial loading on transition metal phosphides and maximal atomic utilization, providing more active sites and, thereby enhancing electrocatalytic activity.

High-efficiency electrocatalytic hydrogen evolution in NiCo-Mo2C tandem nanoreactors with bimetallic modulation and crystal plane synergy

Mo2C, with an electronic structure closely resembling that of Pt, holds significant promise as a catalyst for nonprecious metal-based electrocatalytic hydrogen evolution reactions (HER). This study presents the design and synthesis of Ni and Co bimetallic-doped Mo2C (NiCo-Mo2C) tandem nanoreactors, engineered by leveraging the concept of a high-gain transistor cascade amplifier. In NiCo-Mo2C material, each monomer layer on Mo2C rod functions as an individual electrocatalytic nanoreactor, with the rod supporting a tandem configuration of these units. The combined modulation of Ni and Co at NiCo-Mo2C interface increases the electron cloud density around Mo and shifts the d-band center negatively, effectively reducing Mo-H* binding energy. The synergy between NiCo-Mo2C (101) and (002) crystal planes facilitates both water dissociation and H* desorption from Mo sites. This tandem configuration of multicatalytic units achieves enhanced hydrogen evolution, demonstrated by the low overpotential at 10 mA·cm-2 (η10) values of 129 mV and 180 mV and Tafel slopes of 84 mV·dec-1 and 85 mV·dec-1 in 1 M KOH and 0.5 M H2SO4, respectively. Through bimetallic modulation, crystal plane synergy, and tandem structuring, this work advances a novel approach to optimizing HER kinetics, presenting a valuable strategy for developing highly efficient, nonprecious metal-based electrocatalysts.

Constructing core-shell phosphorus doped MnCo2O4.5@ZIS for efficient photocatalytic hydrogen production from water splitting

Rational construction of core@shell heterostructured photocatalysts is the key to realize efficient hydrogen production from water splitting attributing to the accelerated photoinduced charges separation/transfer and enhanced light absorption ability. In this work, two-dimensional (2D) ZnIn2S4 (ZIS) nanosheets were in-situ grown on phosphorus doped MnCo2O4.5 (P-MnCo2O4.5) nanospheres to construct P-MnCo2O4.5@ZIS heterostructured photocatalysts for efficient photocatalytic hydrogen production. The optimized 6 wt% P-MnCo2O4.5@ZIS composite presents remarkable photocatalytic hydrogen evolution rate of 4197 µmol g-1 h-1 (8 times of single ZIS) along with excellent cycling stability, which is comparable to most previous reported ZnIn2S4-based or even noble-metal involved catalysts. The improved photocatalytic performance is resulted from the distinguished heterostructure and components of P-MnCo2O4.5@ZIS, in which the close contact interface facilitates the separation/transfer and inhibits the recombination of charges, and the uniform distribution of ZIS nanosheets on P-MnCo2O4.5 increases the active sites and fortifies the light absorption. The present work comes up with a prospective method for establishing core@shell ZIS-based heterostructured photocatalysts for efficient hydrogen generation.

Coordinated d-p hybridized hcp@fcc NiRu alloy doped by interstitial atoms for boosting urea-assisted simulated seawater electrolysis at industrial current densities

The production of hydrogen through seawater electrolysis has recently garnered increasing concern. However, hydrogen evolution reaction (HER) by alkaline seawater electrocatalysis is severely impeded by the slow H2O adsorption and H* binding kinetics at industrial current densities. Herein, a face-centered cubic/hexagonal close packed (fcc/hcp) NiRu alloy heterojunction was fabricated on Ni foam (N doped NiRu-inf/NF) by a low-temperature nitrogen plasma activation. Simultaneously, nitrogen atoms are introduced into the alloy to facilitate d-p hybridization. When N doped NiRu-inf/NF is integrated into a dual-electrode cell for urea-assisted seawater electrolysis, it achieves 100 mA cm-2 with an ultra-low voltage of 1.36 V and excellent stability. Density functional theory (DFT) verifies that the robust d-p hybridization among Ni, Ru and N exhibits more energy level matching for H2O molecule adsorption at the Ru sites, while simultaneously reducing the interaction between H* and Ni sites in N-doped NiRu-inf.

Self-supported Ru-Fe-Ox nanospheres as efficient electrocatalyst to boost overall water-splitting in acid and alkaline media

Developing electrocatalysts with high activity and durability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both acidic and alkaline electrolytes remains challenging. In this study, we synthesize a self-supported ruthenium-iron oxide on carbon cloth (Ru-Fe-Ox/CC) using solvothermal methods followed by air calcination. The morphology of the nanoparticle exposes numerous active sites vital for electrocatalysis. Additionally, the strong electronic interaction between Ru and Fe enhances electrocatalytic kinetics optimization. The porous structure of the carbon cloth matrix facilitates mass transport, improving electrolyte penetration and bubble release. Consequently, Ru-Fe-Ox/CC demonstrates excellent catalytic performance, achieving low overpotentials of 32 mV and 28 mV for HER and 216 mV and 228 mV for OER in acidic and alkaline electrolytes, respectively. Notably, only 1.48 V and 1.46 V are required to reach 10 mA cm-2 for efficient water-splitting in both mediums, exhibiting remarkable stability. This research offers insights into designing versatile, highly efficient catalysts suitable for varied pH conditions.

Platinum Cluster Decoration on Hollow Carbon Spheres for High-Efficiency Hydrogen Evolution Reaction

Currently, platinum (Pt)/carbon support composite materials have tremendous application prospects in the hydrogen evolution reaction (HER). However, one of the primary challenges for boosting their performance is designing a substrate with the desired microstructure. Herein, the intact hollow carbon spheres (HCSs) were prepared via template method. Based on the morphology variation of the as-prepared HCSs-x, we conjectured that the polydopamine (PDA) core was generated first and then slowly grew into a complete overburden (SiO2@PDA). Afterward, Pt atomic clusters were anchored on the outer shells of HCSs-4 to construct composite electrocatalysts (Pty/HCSs-4) by a chemical reduction method. Due to the low charge-transfer resistance, the HCSs have a large electrochemical surface area and provide a continuous electron transport pathway, boosting the atom utilization efficiency during hydrogen production and release. The synthesized Pt2.5/HCSs-4 electrocatalysts exhibit excellent HER activity in acidic media, which can be ascribed to the compositional modulation and delicate structural design. Specifically, when the overpotential is 10 A g-1, the overpotential can achieve 92 mV. This work opens a new route to fabricate Pt-based electrocatalysts and brings a new understanding of the formation mechanism of HCSs.

Cation vacancy modulated Cu3P-CoP heterostructure electrocatalyst for boosting hydrogen evolution at high current densities and coupling Zn-H2O battery

Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported Cu3P-CoP heterostructure electrocatalyst with cation vacancy defects (defined as Cu3P-CoP-VAl/CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained Cu3P-CoP-VAl/CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm-2, a high turnover frequency value of 1.05 s-1 at an overpotential of 200 mV and a small apparent activation energy (Ea) of 9 kJ·mol-1, while shows superior long-term stability at large current densities of 100 and 240 mA·cm-2. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the Ea, leading to the decrease of the kinetic barriers of Cu3P-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of Cu3P-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of Cu3P-CoP-VAl/CF. More significantly, the alkali-cell assembled by Cu3P-CoP-VAl/CF (cathode) and RuO2/CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm-2 at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-H2O battery with Cu3P-CoP-VAl/CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm-2. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting.

Efficient Hydrogen Production over Molybdenum Tungsten Bimetallic Oxide NF/PMonW12-n Catalyst on Nickel Foam

Developing inexpensive, efficient, and stable catalysts is crucial for reducing the cost of electrolytic hydrogen production. Recently, polyoxometalates (POMs) have gained attention and widespread use due to their excellent electrocatalytic properties. This study designed and synthesized three composite materials, NF/PMonW12-n, by using phosphomolybdic-tungstic heteropolyacids as precursors to grow in situ on nickel foam via the hydrothermal process and subsequent calcination. Then, their catalytic performances are systematically investigated. This work demonstrates that the NF/PMonW12-n catalysts generate more low valent oxides under the synergistic effect of Mo and W, further enhancing activity for hydrogen evolution reaction (HER). Among these electrocatalysts, NF/PMo6W6 exhibits the perfect HER performance, η10 is only 74 mV. It also shows great stability during long-term electrolysis. The current study introduces a fresh approach for producing electrocatalysts that are both cost-effective and highly efficient.

Synthesis and Electrocatalytic Applications of Layer-Structured Metal Chalcogenides Composites

Featured with the attractive properties such as large surface area, unique atomic layer thickness, excellent electronic conductivity, and superior catalytic activity, layered metal chalcogenides (LMCs) have received considerable research attention in electrocatalytic applications. In this review, the approaches developed to synthesize LMCs-based electrocatalysts are summarized. Recent progress in LMCs-based composites for electrochemical energy conversion applications including oxygen reduction reaction, carbon dioxide reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, overall water splitting, and nitrogen reduction reaction is reviewed, and the potential opportunities and practical obstacles for the development of LMCs-based composites as high-performing active substances for electrocatalytic applications are also discussed. This review may provide an inspiring guidance for developing high-performance LMCs for electrochemical energy conversion applications.

Agglomeration inhibition engineering of nickel-cobalt alloys by a sacrificial template for efficient urea electrolysis

Designing efficient non-precious metal-based catalysts for urea oxidation reaction (UOR) is essential for achieving energy-saving hydrogen production and the treatment of wastewater containing ammonia. In this study, sodium dodecyl sulfate (SDS) is employed as a sacrificial template to synthesize NiCo alloy nanowires (NiCo(SDS)/CC), and the instinct formation mechanism is investigated. It is found that SDS can inhibit the Ostwald ripening during hydrothermal and calcination processes, which could release abundant active cobalt, thereby modulating the electronic structure to promote the catalytic reaction. Moreover, SDS as a sacrificial template can induce the deposition of metal atoms and increase the specific surface area of the catalyst, providing abundant active sites to accelerate the reaction kinetics. As expected, the NiCo(SDS)/CC exhibits good activity for both UOR and hydrogen evolution reactions (HER) and it requires only 1.31 V and -86 mV to obtain a current density of ±10 mA cm-2, respectively. This work provides a new strategy for reducing the agglomeration of transition metals to design high-performance composite catalysts for urea oxidation.

Renovated FeCoP-NC nanospheres wrapped by CoP-NC nanopetals: As a tremendously effectual and robust MOF-assisted electrocatalyst for hydrogen energy production

The future of energy technology is significantly influenced by hydrogen (H2) energy. However, hydrogen energy production through water-splitting entirely depends on the catalyst's performance. Modifying the morphological structure and increasing the number of active sites by changing the metal composition are pivotal factors in enhancing the catalytic activity for the hydrogen evolution reaction (HER). In this context, we introduce the impact of metal-organic framework (MOF) strategies for decorating CoP petals onto α-Fe2O3 and FeCoP-NC (NC-nitrogen-doped carbon) nanoflowers. This method results in an excellent electrocatalyst for HER. The study demonstrated the influence of different MOF precursors, the impact of calcination temperatures, and the importance of composition percentages in Fe1-xCoxP-NC. As a result, FeCoP-NC shows excellent electrochemical performance potential (η) of 57 mV, a rapid kinetic Tafel value of 61 mV/dec, and remarkable electrochemical stability of around 2000 cycles and 20 h in stand potential. Additionally, the composite has numerous active surfaces at 4.7 mF/cm2 during the electrochemical reactions. This work concludes that MOF-assisted FeCoP-NC nanoflowers are an ideal electrocatalyst for HER in an alkaline medium.

Remodeling the Electronic Structure of Metallic Nickel and Ruthenium via Alloying in a Molecular Template for Sustainable Hydrogen Evolution

The reasonably constructed high-performance electrocatalyst is crucial to achieve sustainable electrocatalytic water splitting. Alloying is a prospective approach to effectively boost the activity of metal electrocatalysts. However, it is a difficult subject for the controllable synthesis of small alloying nanostructures with high dispersion and robustness, preventing further application of alloy catalysts. Herein, we propose a well-defined molecular template to fabricate a highly dispersed NiRu alloy with ultrasmall size. The catalyst presents superior alkaline hydrogen evolution reaction (HER) performance featuring an overpotential as low as 20.6 ± 0.9 mV at 10 mA·cm-2. Particularly, it can work steadily for long periods of time at industrial-grade current densities of 0.5 and 1.0 A·cm-2 merely demanding low overpotentials of 65.7 ± 2.1 and 127.3 ± 4.3 mV, respectively. Spectral experiments and theoretical calculations revealed that alloying can change the d-band center of both Ni and Ru by remodeling the electron distribution and then optimizing the adsorption of intermediates to decrease the water dissociation energy barrier. Our research not only demonstrates the tremendous potential of molecular templates in architecting highly active ultrafine nanoalloy but also deepens the understanding of water electrolysis mechanism on alloy catalysts.

Synergistic Effects of Pyrrolic N/Pyridinic N on Ultrafast Microwave Synthesized Porous CoP/Ni2P to Boost Electrocatalytic Hydrogen Generation

Transition metal phosphides are ideal inexpensive electrocatalysts for water-splitting, but the catalytic activity still falls behind that of noble metal catalysts. Therefore, developing valid strategies to boost the electrocatalytic activity is urgent to promote large-scale applications. Herein, a microwave combustion strategy (20 s) is applied to synthesize N-doped CoP/Ni2P heterojunctions (N-CoP/Ni2P) with porous structure. The porous structure expands the specific surface area and accelerates the mass transport efficiency. Importantly, the pyrrolic N/pyridinic N content is adjusted by changing the amount of urea during the synthesis process and then optimizing the adsorption/desorption capacity for H*/OH* to enhance the catalyst activity. Then, the synthesized N-CoP/Ni2P exhibits small overpotentials of 111 and 133 mV for HER in acidic and alkaline electrolytes and 290 mV for OER in alkaline electrolytes. This work provides an original and efficient approach to the synthesis of porous metal phosphides.