Low Tafel Slope Research Articles

In-situ synthesis of bifunctional N-doped CoFe₂O₄/rGO composites for enhanced electrocatalysis in hydrogen and oxygen evolution reactions

The development of cost-effective and efficient materials for electrochemical water splitting using non-noble metal oxide is a promising strategy to promote clean energy and mitigate environmental issues. In this study, we synthesized N-doped CoFe2O4 (NCF) and various wt% rGO-loaded N-doped CoFe2O4 (x = 1 %, 3 %, and 5 %; denoted as NCFRx) using a hydrothermal method. Subsequently, the NCF and NCFR3 samples were annealed at four different temperatures (y = 550, 600, 650, and 700 °C; denoted as NCFR3-y). FE-SEM, TEM, and XPS studies revealed a strong interface between rGO nanosheets and N-doped CF, acting as electron transport carriers that enhance performance in hydrogen and oxygen evolution reactions (HER and OER). The electrochemical evaluation of the prepared materials was carried out in a 1.0 M KOH electrolyte. The nickel foam (NF) electrode supported by the NCFR3–650 composite demonstrated excellent and stable electrocatalytic performance with a minimum overpotential of 73 mV and 170 mV at a current density of 10 mA/cm2 for HER and OER, respectively, and achieved excellent faradaic efficiencies of 91.01 % for OER and 90.48 % for HER. These results confirmed that the NCFR3–650@NF composite catalyst was comparable to standard Pt/C and IrO2, exhibiting lower overpotential and Tafel slope at a current density of 10 mA/cm2. The double layer capacitance (Cdl) of NCFR3–650@NF (7.70 mF/cm2) was higher than that of other electrocatalysts, indicating a large electrochemically active surface area. The structural properties of NCFR3–650@NF contributed to improved stability during long-term HER and OER analysis. Therefore, the developed NCFR3–650@NF electrocatalyst is a promising alternative to noble metal-centered systems for water splitting, offering overall high efficiency.

Enhanced electrocatalytic CO2 reduction into formate: Unleashing the effect of engineered bimetallic oxides supported on activated carbon

The excessive concentration of anthropogenic CO2 continuously harms the atmosphere. Consequently, deploying CO2 via the electrochemical reduction approach has become a highly sought-after research thrust area. In this study, a facile, one-pot solution combustion synthesis method (SCSM) was employed for the synthesis of various mixed-metal oxides supported on porous activated carbon (SnO2-CuO@AC). The prepared materials are characterized by analytical and spectroscopic techniques. Electrochemical studies were performed for the SnO2-CuO@AC catalyst to reduce CO2 into formic acid via an electrochemical approach. The in-depth properties of the designed catalysts were analysed by theoretical calculations using FT-IR and XRD data. The SnO2-CuO@AC exhibited improved electrochemical performance with a high current density of −10.77 mAcm−2, a low overpotential of −1.29 V, a lower Tafel slope value of 100 mV/dec. The faradaic efficiency for formic acid was 78.8 % at 1.3 V vs. RHE, with high stability for 9 h. The presence of coordinated active sites and oxygen vacancies, and a lower Tafel slope, also endorses CO2 adsorption and activation, faster electron transfer and boosts CO2 reduction. The significant reactivity toward CO2 reduction is attributed to the intensity of interaction between CO2∗- and the electrocatalyst, followed by kinetic activation toward protonation to obtain the desired product.

The Construction of Face-to-Face Combination between NiFe-layered Double Hydroxide Nanosheets and Monolayer rGO for Efficient Water Splitting and Oxygen Reduction.

Developing cost-effective and efficient electrocatalysts is essential for advancing a green energy future. Herein, a NiFe-layered double hydroxide loaded on reduced graphene oxide (NiFe-LDHs@rGO) hybrid was synthesized using a straightforward three-step process involving exfoliation tearing, electrostatic self-assembly, and chemical reduction. The face-to-face packing and ultrathin exfoliation enable strong heterogeneous interactions, fully harnessing the potential of these complementary two-dimensional counterparts. Consequently, the resultant catalyst displays outstanding oxygen evolution reaction (OER) catalytic activity and stability, whose overpotential is as low as 241 mV at 30 mA cm-2 and 255 mV at 50 mA cm-2 with a low Tafel slope of 62.1 mV dec-1. Both the experimental results and density functional theory (DFT) calculations reveal that the face-to-face assembly strengthens the electronic interactions between NiFe-LDHs and rGO, which effectively modulates the d-band center of Ni and Fesites and improves the reaction kinetics for OER. Moreover, the resultant NiFe-LDHs@rGO hybrids exhibit excellent multifunctional catalytic performance. Its hydrogen evolution reaction (HER) activity is endowed by Fe-site of NiFe-LDHs and defect states rGO and achieves a low voltage of 1.68 V to drive a current density of 10 mA cm-2 for overall water splitting. The face-to-face heteroassembly also imparts NiFe-LDHs@rGO with superior oxygen reduction reaction (ORR) activity, with a half-wave potential of 0.70 V and a limiting current density of 4.2 mA cm-2. Its ORR primarily follows a four-electron transfer pathway with a minor contribution from a two-electron process. This study establishes the groundwork for optimizing two-dimensional heterogeneous interfaces in LDH@carbon-based materials for advanced energy conversion.

Electrocatalysis of Co/CoxOy nanofilms supported by synchronously nitrogen-doped Ketjenblack carbon towards oxygen reduction reaction

Developing a highly active and stable non-precious metal catalyst for oxygen reduction reaction (ORR) is of great practical significance for advancing fuel cell technology. In this work, a continuous two-step hydrothermal reaction followed by high temperature pyrolysis were employed to achieve in situ N-doping preferentially into Ketjenblack carbon (KB-N) and composite of KB-N and Co/CoxOy nanofilms (Co/CoxOy-NFs) as Co/CoxOy-NFs@KB-N. The N-doped state strongly affects the ORR activity of catalyst. All prepared Co/CoxOy-NFs@KB-N catalysts exhibit observably improved ORR activity compared with the basal KB-N and N-doped Co/CoxOy-NFs, in which the optimal Co/CoxOy-NFs@KB-N catalyst demonstrate the positive Eonset (0.864 V) and E1/2 (0.788 V) vs. RHE, the low Tafel slope (69.27 mV dec−1), implying quick ORR kinetics. And, the Co/CoxOy-NFs@KB-N catalyst exhibits highly electrochemical durability. The KB-N substrate can purify Co valence in CoO component, promote amorphization of CoO crystalline structure and enhance the interaction between Co/CoxOy-NFs and KB-N in Co/CoxOy-NFs@KB-N catalyst. Thus electronic effect, structural effect and synergistic effect can strengthen O2 adsorption, provide enough adsorbed sites and accelerate electron transfer, resulting in prominent ORR performance of Co/CoxOy-NFs@KB-N catalyst.

Facile synthesis of transition metal-selenides@CNTs for electrochemical oxygen evolution reactions

The fabrication of carbon based efficient electrocatalysts for hydrogen production during electrochemical water splitting could be a great achievement to fulfill the future renewable energy demand. In this study, one-step hydrothermal process was used to develop composites of multi-metal selenides with carbon nanotubes (MnSe@CNTs, MnCuSe@CNTs, MnCoNiSe@CNTs) as electrocatalysts for OER during electrolytic water splitting. XRD and SEM with EDS analysis confirm the successful fabrication of proposed catalyst and their crystalline morphology. Among the synthesized functionalized CNTs composites, bimetallic selenide composite gives a better electrocatalytic activity with the reduce overpotential, lower Tafel slope and reduced charge transfer resistance in 1 M KOH. By using this catalyst, water oxidation starts at 1.4 V onset potential with a very low overpotential of 245 mV and the Tafel slope was only 107 mV dec−1. Metal based selenides composites with CNTs introduces a lot of active sites, subsequent nanoparticles of MnSe, MnCuSe, & MnCoNiSe, causes to boost the surface area and electrocatalysis towards oxygen evolution reactions.

Unveiling the bi-functional electrocatalytic properties of rhenium di-sulfide nanostructures towards the development of high-rate alkaline water electrolyzer

Alkaline water electrolyzer (AWE) offers a unique solution for generating hydrogen (H2) gas via an electrochemical water-splitting process. The major drawback of the AWE is its limitations in driving high-current densities, an important criterion for the industry standard. In this work, we have demonstrated the bi-functional electrocatalytic properties of ReS2 nanosheets towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with low overpotential (139.2 and 258.89 mV for HER and OER) and Tafel slopes, respectively. The micro/nano electrocatalytic activity of the ReS2 electrocatalyst was examined using a scanning electrochemical microscope (SECM) and Kelvin probe force microscope (KPFM). A lab-scale AWE fabricated using prototype ReS2 electrocatalyst demonstrated that they could drive the benchmark current density (10 mA cm−2) with a low cell voltage of 1.645 V. Further, we also demonstrated a self-powered system comprising an on-shore wind-energy driven ReS2 AWE for sustainable H2 production. Further, the experimental results based on industrially recommended conditions for AWE illustrated that they need only 1.85 V to drive a current density of 500 mA cm−2; thus, ensuring their candidature towards high-rate AWE for clean hydrogen production.

Molten salt electrolytic CO2-derived NiCo2@C catalysts with enhanced oxygen evolution reaction

Carbon-based nonprecious metallic electrocatalysts have garnered considerable attention due to their tunable structures, rapid electron transfer, and easy characterization. There is great anticipation for the development of green and controllable methods for metal-carbon-based electrocatalysts. Molten salts synthesis offers a green, facile and effective approach for fabricating carbon-based materials, utilizing carbon dioxide (CO2) as the carbon source. In this study, the co-electroreduction of CO2 and the binary metal oxide NiCo2O4 is carried out in a mixture of Li2CO3, Na2CO3, and K2CO3 at 500oC. This process leads to the formation of metal alloy nanoparticles encapsulated in a carbon matrix derived from CO2, referred to as NiCo2@C. The resulting NiCo2@C exhibits low overpotential and Tafel slope (340mV@10mAcm−2, 67mV dec−1) in 0.1M KOH solution for OER, which is superior to the commercial RuO2 (360mV@10mAcm−2, 88mV dec−1). Both experimental and theoretical findings indicate the synergistic effects of Ni/Co bimetallic sites. Spontaneous adsorption of hydroxide ion on the bridging sites of heterologous diatoms facilitates the adsorption and desorption of intermediates during the OER process.

Enhanced Zinc-air battery performance and local electrochemical evaluation of atomically dispersed Co and Ni in S, N-codoped carbon nanofibers via scanning electrochemical microscopy

This study reports the successful synthesis of a novel electrocatalyst for oxygen reduction reactions (ORR), comprising S,N dual-doped carbon nanofibers with atomically dispersed Co/Ni species (denoted as Co,Ni-SAs/S,N-CNFs), leveraging electrostatic spinning to achieve a unique spatial architecture that maximizes both active site density and mass transport efficiency. Density functional theory (DFT) analysis identified the initial proton-electron transfer to adsorbed O2 as the rate-limiting step, with CoN3S1-NiN3S1 emerging as the pivotal active site structure catalyzing this critical reaction. The fabricated Co,Ni-SAs/S,N-CNFs electrocatalyst exhibited remarkable ORR performance, characterized by a high half-wave potential of 0.84 V and a low Tafel slope of 57.9 mV dec-1. To gain a comprehensive understanding of its catalytic behavior, a tailored temperature-controlled scanning electrochemical microscopy (SECM) was employed, enabling the mapping of reactivity distribution under simulated operating conditions while preserving structural integrity. Liquid zinc-air batteries (ZABs) with this electrocatalyst excelled, reaching 175 mW/cm2 power density and enduring 1240 cycles. The electrospun membrane catalyst enabled both button and flexible ZABs, adaptable to diverse environments. This study advances non-precious metal electrocatalyst design and offers insights for ZAB applications, fostering green energy prospects.

Evaluating the Hydrogen Evolution Reaction Activity of Colloidally Prepared PtSe2 and PtTe2 Catalysts in an Alkaline Medium.

The hydrogen evolution reaction (HER) in alkaline electrolytes using transition metal dichalcogenides is a research area that is not tapped into. Alkaline HER ( ) is harder to achieve relative to acidic HER ( ), this is attributed to the additional water dissociation step that occurs in basic HER to generate H+ ions. In fact, for most catalysts, their HER activity decreases tremendously when the electrolyte is changed from acidic to basic conditions. Platinum dichalcogenides, PtX2 (X=S, Se, Te), are an interesting member of transition metal dichalcogenides (TMDs) as these show an immense hybridization of the Pt d orbitals and chalcogen p orbitals because of closely correlated orbital energies. The trend in electronic properties of these materials changes drastically as the chalcogen is changed, with PtS2 reported to exhibit semi-conductor properties, PtSe2 is semi-metallic or semi-conductive, depending on the number of layers, while PtTe2 is metallic. The effect of varying the chalcogen atom on the HER activity of Pt dichalcogenides will be studied. Pt dichalcogenides have previously been prepared by direct high-temperature chalcogen deposition of Pt substrate and evaluated as electrocatalysts for HER in H2SO4. The previously employed synthesis procedures for PtX2 limit these compounds' mass production and post-synthesis treatment. In this study, we demonstrated, for the first time the preparation of PtSe2 and PtTe2 by colloidal synthesis. Colloidal synthesis offers the possibility of large-scale synthesis of materials and affords the employment of the colloids at various concentrations in ink formulation. The electrochemical HER results acquired in 1 M KOH indicate that PtTe2 has a superior HER catalytic activity to PtSe2. A potential of 108 mV for PtTe2 and 161 mV for PtSe2 is required to produce a current density of -10 mA cm-2 from these catalysts. PtTe2 has a low Tafel slope of 79 mVdec-1, indicating faster HER kinetics on PtTe2. Nonetheless, the stability of these catalysts in an alkaline medium needs to be improved to render them excellent HER electrocatalysts.

Comparative study of zinc sulfide, tin selenide, and their composite electrocatalysts for oxygen evolution reaction: Towards efficient and stable water splitting

Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are critical processes in electrochemical water splitting, driving demand for efficient and durable electrocatalysts. This study presents a comprehensive evaluation of water splitting performance of ZnS@SnSe2 nano–composite in 1.0 M KOH solution. With ZnS nanoparticles decorated on SnSe2, exhibited remarkable catalytic activity for both HER and OER. ZnS@SnSe₂ composite demonstrated an low overpotential of 22 mV to reach a current density of 10 mA cm-2, outperforming ZnS (245 mV) and SnSe2 (280 mV). Furthermore, it achieved a Tafel slope of 25 mV dec‑1 and a charge transfer resistance (Rct) of 5.2 Ω, reflecting its enhanced kinetics compared to ZnS (101 mV dec‑1, Rct = 35 Ω) and SnSe2 (230 mV dec‑1, Rct = 7.5 Ω). These results are even competitive with benchmark Pt/C catalyst (30 mV overpotential, 46 mV dec‑1, and 2.2 Ω Rct), highlighting efficiency of composite for hydrogen production. For OER, ZnS@SnSe2 composite required an overpotential of 234 mV to reach 10 mA cm⁻², a substantial improvement over ZnS (361 mV) and SnSe2 (375 mV). Composite showcased a low Tafel slope of 48 mV dec‑1 and an Rct of 1.5 Ω, comparable to commercial RuO2 catalyst (44 mV dec‑1, Rct = 2.2 Ω), further underscoring its superior oxygen evolution capabilities. In practical device configuration, ZnS@SnSe₂/NF electrode achieved a Tafel slope of 21.335 mV dec‑1 for HER and 58.028 mV dec‑1 for OER, demonstrating its bifunctional efficiency in a two-electrode system. The device exhibited exceptional long-term stability over 50 h of continuous operation, highlighting its potential for scalable and sustainable water splitting applications.

NiO/ATO as an efficient bifunctional electrocatalysts for oxygen evolution and urea oxidation reactions

In this study, Ni-MOF-derived NiO was mixed with various weights of commercial antimony-doped tin oxide (ATO) using a simple and efficient hydrothermal method to synthesize composites denoted as AN-1, AN-2, and AN-3, which were subsequently characterized using a variety of physicochemical methods. The as-prepared materials were used as bifunctional electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR). In the UOR, the AN-1 electrocatalyst exhibited excellent performance compared to the other electrocatalysts. In a 1.0 M KOH aqueous electrolyte, the OER onset potential was approximately 1.64 V, whereas, in the UOR, the overpotential was 1.38 V (vs RHE), which is lower than that of the OER. The AN-1 electrocatalyst showed lower Tafel slope values in both the OER and UOR studies: 173 mV dec−1 and 109mV dec−1, respectively.

Doping-mediated interface engineered Ni3S2: Economically viable electrochemical methanol-mediated water splitting

Electrochemical water splitting is the front runner to meet the global green hydrogen demand. The development of a noble metal-free earth-abundant electrocatalyst is desired to rationalize an economically viable electrochemical water-splitting system. The sluggish anodic oxygen evolution reaction (OER) is the bottleneck of the electrochemical water-splitting system. Herein, to improve OER kinetics, group VIB elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) doped nickel sulfides (Ni3S2) nanosheets (NSs) are synthesized by two-step hydrothermal method to modulate the intrinsic electrocatalytic activity of the pure Ni3S2. Among all the doped samples, the Cr-doped Ni3S2 catalyst exhibited excellent OER with an ultra-low overpotential of 248 mV and MOR with a potential of 1.36 V @ 10 mA cm−2 vs RHE achieving a lower Tafel slope of 95.5 mV/dec and 46.4 mV/dec and outstanding durability with negligible degradation respectively. Furthermore, the Pt/C||Cr-Ni3S2 (1.48 V) system outperforms commercial Pt/C||RuO2 (1.53 V @ 10 mA cm−2) in a two-electrode configuration. The methanol-mediated hybrid water splitting system only warranted a cell voltage of 1.38 V to attain 10 mA cm−2 for the Pt/C||Cr-Ni3S2 system in the presence of 0.1 M methanol (MeOH). The methanol oxidation reaction (MOR) mediated the hybrid water electrolyzer system demonstrates reduced operation cell voltage while additionally electro-synthesizing formate as a value-added chemical. The overall work is motivated to rationalize the importance of doping-mediated interface-engineered catalyst synthesis to improve the electrocatalytic efficiency of the hybrid water electrolyzer.

Uniform carbon pillars array grown on boron doped diamond for high-performance supercapacitors and hydrogen evolution reactions

Carbon materials have marvelous ability in energy storage and microelectronics as a result of the high specific surface area and electrical conductivity. However, the low stability and the low power density caused by low potential window make it particularly difficult for their application in aqueous electrolysis. In this study, boron doped diamond (BDD) with wide potential window is used as substrate and Ni as catalyst to grow uniform carbon pillars (CP) by microwave plasma chemical vapor deposition method. The composite structure (CP/BDD) yields significant specific capacity (91.64 mF cm−2 at 0.1 mA cm−2) and cycling stability (92.3 % retention rate after 20,000 cycles) when used as the electrode of supercapacitors, superior to most of BDD-based electrodes. The prepared symmetrical supercapacitor devices maintain their excellent electrochemical performance characteristics (power density of 4.4 mW cm−2 and energy density of 13.4 μW h cm−2), as well as high cycling stability. In addition, the electrode has considerable application potential in electrochemical hydrogen production with low hydrogen evolution potential and small Tafel slope value. These results illustrate the potential of BDD based composites for using as energy storage electrodes for electronic products and energy conversion equipment.

Harnessing dysprosium telluride/GPE as an effective electrode for energy storage and conversion

Hydrogen stands out as a clean alternative to fossil fuels, and its production via water electrolysis is promising, although the slow kinetics of the oxygen evolution reaction (OER) pose a significant challenge. Alongside energy conversion, the quest for effective energy storage remains critical. This study explores the potential of dysprosium telluride (Dy2Te3) as a highly efficient catalyst for OER and a supercapacitor electrode. The hydrothermally synthesized Dy2Te3 exhibits exceptional OER activity, characterized by an overpotential of 294 mV at 1.48 V vs. RHE, a low Tafel slope of 48 mV dec−1, and minimal interfacial resistance of 13 Ω. In a 1.0 M KOH solution, Dy2Te3 nanoparticles demonstrate outstanding supercapacitor performance, achieving a power density of 283.5 W kg−1, specific capacitance of 645.33 F g−1, and energy density of 22.8 Wh kg−1 at 1 A g−1. The high performance is attributed to enhanced electrical conductivity and a low impedance of 0.352 Ω in a three-electrode system. In a practical two-electrode configuration, Dy2Te3 nanoparticles deliver a specific capacitance of 479 F g−1, energy density of 94 Wh kg−1, and power density of 0.32 kW kg−1, with a reduced interfacial resistance of 1.03 Ω. These results underscore the potential of Dy2Te3 as a viable electrode material for both supercapacitors and water splitting, offering valuable insights into the application of lanthanide-based metal chalcogenides in energy technologies.

Platinum/Platinum Sulfide on Sulfur-Doped Carbon Nanosheets with Multiple Interfaces toward High Hydrogen Evolution Activity.

Platinum (Pt)-based materials are among the most competitive electrocatalysts for the hydrogen evolution reaction (HER) due to suitable hydrogen adsorption energy. Due to the rarity of Pt, it is desirable to develop cost-effective Pt-based electrocatalysts with low Pt loading. Herein, Pt/PtS electrocatalysts on S-doped carbon nanofilms (PPS/C) have been successfully fabricated through a precursor reduction route with a complex of Pt and 1-dodecanethiol (1-DDT) as the precursor. The PPS/C achieved at 400 °C (PPS/C-400) exhibits excellent HER performances with an ultralow overpotential of 41.3 mV, a low Tafel slope of 43.1 mV dec-1 at a current density of 10 mA cm-2, and a long-term stability of 10 h, superior to many recently reported Pt-based HER electrocatalysts. More importantly, PPS/C-400 shows a high mass-specific activity of 0.362 A mgPt-1 at 30 mV, which is 1.88 times of that of commercial 20% Pt/C (0.193 A mgPt-1). The introduction of sulfur leads to the formation of PtS, which not only reduces the content of Pt but also realizes the interface regulation of Pt/PtS, as well as the doping of carbon. Both regulations make the resulting catalyst have abundant active centers and rapid electron transfer/transport, which is conducive to balancing the adsorption and resolution of intermediate products, and finally achieving great mass-specific activity and stability. The research work may provide ideas for designing effective Pt-based multi-interface electrocatalysts.

Unlocking interfacial effects in NiTiO3-TiO2 eutectic composite: Enhancing overall electrocatalytic and photoelectrochemical water splitting

This study introduces a novel approach to tackle the urgent demand for catalysts possessing both bifunctional capabilities and efficient photocatalytic properties. By employing the micro-pulling down method, a NiTiO3/TiO2 eutectic composite is synthesized, creating an interface rich structure. This composite is utilized as a photo-anode, displaying a significant photocurrent of 3.5 mA/cm2 at 1.4 V. Through annealing in an H2 atmosphere, the catalytic performance is finely adjusted, revealing distinct electrochemical activities at the interface of NiTiO3 and TiO2. Enhanced interfacial adsorption is confirmed by scanning electrochemical microscopy post-annealing. Remarkably, the annealed NiTiO3/TiO2 exhibits outstanding overall water-splitting efficiency, with minimal overpotentials of 80 mV (at 10 mA/cm2) and 120 mV (at 50 mA/cm2) for the HER and OER, respectively. The low Tafel slope (41 mV dec-1) underscores rapid water splitting kinetics. Density functional theory (DFT) calculations suggest that NiTiO3-TiO2 heterostructure can enhanced the catalytic properties of the surface providing higher adsorption of the electrolyte ions during catalytic reactions. This study establishes a straightforward crystal growth strategy for the design of highly effective, enduring, and bifunctional photocatalytic catalysts, signaling promising advancements in water splitting technology.

Enhanced oxygen evolution and power density of Co/Zn@NC@MWCNTs for the application of zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are viewed as a promising solution for electric vehicles due to their potential to provide a clean, cost-effective, and sustainable energy storage system for the next generation. Nevertheless, sluggish kinetics of the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR) at the air electrode, and low power density are significant challenges that hinder the practical application of ZABs. The key to resolving the development of ZABs is developing an affordable, efficient, and stable catalyst with bifunctional catalytic. In this study, we present a series of bifunctional catalysts composed of Co/Zn nanoparticles uniformly embedded in nitrogen-doped carbon (NC) and multi-walled carbon nanotubes (MWCNTs) denoted as Co/Zn@NC@MWCNTs. The incorporation of MWCNTs using a facile and non-toxic method significantly decreased the overpotential of the OER from 570 to 430 mV at 10 mA cm−2 and the peak power density from 226 to 263 mW cm−2. Besides, the electrochemical surface area measurements and electrochemical impedance spectroscopy indicate that the three-dimensional (3D) network structure of MWCNTs facilitates mass transport for ORR and reduces electron transfer resistance during OER, leading to a small potential gap of 0.86 V between OER and ORR, high electron transfer number (3.92–3.98) of the ORR, and lowest Tafel slope (47.8 mV dec−1) of the OER in aqueous ZABs. In addition, in-situ Raman spectroscopy revealed a notable decrease in the ID/IG ratio for the optimally configured Co/Zn@NC@MWCNTs (75:25), indicating a reduction in defect density and improved structural ordering during the electrochemical process, which directly contributes to enhanced ORR activity. Hence, this study provides an excellent strategy for constructing a bifunctional catalyst material with a 3D MWCNTs conductive network for the development of advanced ZAB systems for sustainable energy applications.

WS2 Moiré Superlattices Supporting Au Nanoclusters and Isolated Ru to Boost Hydrogen Production.

Maximizing the catalytic activity of single-atom and nanocluster catalysts through the modulation of the interaction between these components and the corresponding supports is crucial but challenging. Herein, guided by theoretical calculations, a nanoporous bilayer WS2 Moiré superlattices (MSLs) supported Au nanoclusters (NCs) adjacent to Ru single atoms (SAs) (Ru1/Aun-2LWS2) is developed for alkaline hydrogen evolution reaction (HER) for the first time. Theoretical analysis suggests that the induced robust electronic metal-support interaction effect in Ru1/Aun-2LWS2 is prone to promote the charge redistribution among Ru SAs, Au NCs, and WS2 MSLs support, which is beneficial to reduce the energy barrier for water adsorption and thus promoting the subsequent H2 formation. As feedback, the well-designed Ru1/Aun-2LWS2 electrocatalyst exhibits outstanding HER performance with high activity (η10=19mV), low Tafel slope (35mVdec-1), and excellent long-term stability. Further, in situ, experimental studies reveal that the reconstruction of Ru SAs/NCs with S vacancies in Ru1/Aun-2LWS2 structure acts as the main catalytically active center, while high-valence Au NCs are responsible for activating and stabilizing Ru sites to prevent the dissolution and deactivation of active sites. This work offers guidelines for the rational design of high-performance atomic-scale electrocatalysts.

Cobalt-doped graphitic carbon nitride: A multifunctional material for humidity sensing, electrochemical water splitting and environmental remediation applications

Graphitic carbon nitride (g-C3N4) has emerged as a promising eco-friendly material for catalysis and sensing applications due to their unique properties. However, limitations like low specific surface area, insufficient light absorption, and poor conductivity hinder their broader usability. Elemental doping has been established as an effective approach to modify the electronic structure and bandgap of g-C3N4 thus significantly expanding its light-responsive range for enhanced charge separation. This work reports on the fabrication of cost-effective and stable g-C3N4 and cobalt-doped g-C3N4 (Co@g-C3N4) via a simple one-step calcination process. The humidity sensing performance of both g-C3N4 and Co@g-C3N4 was evaluated across a broad humidity range (7 % - 94 % RH) at various testing frequencies. The results demonstrated good reversibility with Co@g-C3N4 exhibiting superior performance compared to pristine g-C3N4. Furthermore, the synthesized materials were assessed for their suitability as photoelectrochemical water splitting catalysts for hydrogen production, representing a step towards energy-efficient fuel cells. Notably, Co@g-C3N4 displayed enhanced performance with a lower onset potential (420 mV) and a lower Tafel slope (65.4 mV dec-1) for the hydrogen evolution reaction (HER) compared to undoped counterparts. Additionally, Co@g-C3N4 nanorods exhibited remarkable performance for the oxygen evolution reaction (OER), showcasing a lower onset potential (1.505 V) and a considerably low overpotential (270 mV), surpassing numerous reported electrocatalysts and even rivaling precious-metal-based ones. Finally, enhanced photocatalytic activities for organic dyes degradation were recorded for the mentioned materials. Therefore, g-C3N4 and related materials have great potential for their industrial electrochemcial applications.

Trifunctional Graphene-Sandwiched Heterojunction-Embedded Layered Lattice Electrocatalyst for High Performance in Zn-Air Battery-Driven Water Splitting.

Zn-air battery (ZAB)-driven water splitting holds great promise as a next-generation energy conversion technology, but its large overpotential, low activity, and poor stability for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) remain obstacles. Here, a trifunctional graphene-sandwiched, heterojunction-embedded layered lattice (G-SHELL) electrocatalyst offering a solution to these challenges are reported. Its hollow core-layered shell morphology promotes ion transport to Co3S4 for OER and graphene-sandwiched MoS2 for ORR/HER, while its heterojunction-induced internal electric fields facilitate electron migration. The structural characteristics of G-SHELL are thoroughly investigated using X-ray absorption spectroscopy. Additionally, atomic-resolution transmission electron microscopy (TEM) images align well with the DFT-relaxed structures and simulated TEM images, further confirming its structure. It exhibits an approximately threefold smaller ORR charge transfer resistance than Pt/C, a lower OER overpotential and Tafel slope than RuO₂, and excellent HER overpotential and Tafel slope, while outlasting noble metals in terms of durability. Ex situ X-ray photoelectron spectroscopy analysis under varying potentials by examining the peak shifts and ratios (Co2+/Co3+ and Mo4+/Mo6+) elucidates electrocatalytic reaction mechanisms. Furthermore, the ZAB with G-SHELL outperforms Pt/C+RuO2 in terms of energy density (797Wh kg-1) and peak power density (275.8mW cm-2), realizing the ZAB-driven water splitting.