Electrochemical Active Surface Area Research Articles

Developing TiCo2O4 spinel based on rGO nanosheet to enhance electrochemical performance of OER activity

The reduction of fossil fuel reserves and the deterioration of environmental conditions have led to a worldwide concern with producing significant amounts of energy in a sustainable manner. The production of electrocatalysts for the oxygen evolution reaction (OER) is imperative for widespread commercialization of water electrolyzers. The electrocatalysts must exhibit improved electrocatalytic behavior while being cost-effective. This work presents simple hydrothermal route for producing a TiCo2O4 nanostructure with a spherical morphology, which is supported on reduced graphene oxide sheets (rGO). The nanocomposite has been subjected to an investigation of its morphological, structural and electrochemical characteristics. This material exhibits promise for electrochemical water splitting due to its significant electroactive surface area, distinctive morphology and metal ions (M+) synergetic effect on its electrocatalytic performance. The nanostructure of TiCo2O4/rGO-has been observed to exhibit robust electrocatalytic activity, underscoring the significance of the present study. Additionally, presented are the enduring stability of the OER, along with the reduced overpotential (269 mV@10 mA cm−2), decreased Tafel slope (37.56 mV dec-1) with greater electrochemical active surface area. Our finding suggests that the TiCo2O4/rGO nanohybrid exhibited high electrocatalytic efficiency and can be utilized in diverse electrochemical applications.

Incorporation of Pd Catalyst into Highly Effective Borophene Nanosheet Co-Catalyst for Electrokinetics and Electrochemical Oxygen Reduction Reactions

AbstractTo improve the performance of the system, it is of great importance to develop efficient catalysts for ethanol (EtOH) electro-oxidation. Pd/B electrocatalyst was synthesized using a sonochemical method. Structural and electrochemical properties of the prepared nanomaterial were investigated using electrochemical and physical techniques such as Raman spectroscopy, electrochemical impedance spectroscopy (EIS), x-ray diffraction (XRD), zetersizer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive x-ray spectroscopy (EDS) and cyclic voltammetry (CV). FTIR confirmed all the functional groups of carbon black, Pd/C, borophene, and Pd/B, and the crystallinity was investigated using XRD. EIS showed that Pd/B has a faster charge transfer and, through investigation using CV, Pd/B showed a more negative onset potential and higher current (−0.76 V vs. Ag|AgCl; 0.07 mA) than Pd/C (−0.65 V vs. Ag|AgCl; 0.05 mA), indicating a more catalytic behavior and tolerance of Pd/B. The active sites could be attributed to the addition of borophene. During the anodic sweeping direction of Pd/B electrocatalyst, it was observed that the ratio of backward peak current (Ibwd) to forward peak current (Ifwd), (Ibwd/Ifwd) of in a 2 M of NaOH + 2 M of EtOH is almost equal to (Ibwd/Ifwd) 1 which shows excellent tolerance of Pd/B to poisoning by ethanol intermediate species. The electron transfer rate (Ks) values for Pd/B at 0.1 M, 0.5 M, 1 M, 1.5 M, and 2 M were estimated to be 4.50 × 10−13 s−1, 1.08 × 10−12 s−1, 4.28 × 10−13 s−1, 5.25 × 10−14 s−1 and 9.35 × 10-14 s−1. At 2 M there is a faster electron transfer than at other concentrations which is also evidenced by the obtained diffusion values (D) of the system which were found to be 2.92 × 10−7 cm2 s−1, 4.72 × 10−8 cm2 s−1, 4.82 × 10−8 cm2 s−1, 1.22 × 10−7 cm2 s−1, and 9.12 × 10−8 cm2 s−1. The electrochemically active surface area (ECSA) is strongly related to intrinsic activity, Pd/B (1.85 cm2/mg × 10−5 cm2/mg) denotes the highest Pd-O stripping charge than Pd/C (1.13 cm2/mg × 10−5 cm2/mg).

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates.

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, we report a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieved high capacitance up to ∼277.5 F cm-3 under an ultrahigh scan rate of 1000mV s-1 with a lower charge-transfer resistance and nearly ten-fold higher electrochemical active surface area than the 2H-MoS2 electrode. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1 mgNaCl cm-3 in CDI experiments. Ex-situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact two-dimensional layered nanolaminates with high volumetric performance for CDI desalination. This article is protected by copyright. All rights reserved.

Structurally Tunable Graphitized Mesoporous Carbon for Enhancing the Accessibility and Durability of Cathode Pt‐Based Catalysts for Proton Exchange Membrane Fuel Cells

Low Pt utilization and intense carbon corrosion of cathode catalysts is a crucial issue for high‐efficiency proton exchange membrane fuel cells due to the highly demanded long‐term durability and less acquisition/application cost. Herein, structurally tunable graphitized mesoporous carbon (GMC) is obtained by direct high‐temperature pyrolysis and in situ‐controlled mesopore formation; the structure‐optimized GMC1300‐1800 exhibits a mesopore size of 7.54 nm and enhanced corrosion resistance. Functionalized GMC1300‐1800 is loaded with small‐sized Pt nanoparticles (NPs) (1.5 nm) uniformly by impregnation method to obtain Pt/GMC1300‐1800 and form an “internal platinum structure” to avoid sulfonic acid groups poisoning as well as ensure O2/proton accessibility. Hence, the electrochemically active surface area (ECSA) of Pt/GMC1300‐1800 reaches 106.1 m2 g−1Pt, while mass activity and specific activity at 0.9 V are 2.1 and 1.4 times those of commercial Pt/C, respectively. Notably, the ECSA decay is less than 17% for both 30 000 cycles’ accelerated durability tests (ADTs) of Pt attenuation and carbon attenuation. Accordingly, the optimized mesoporous structure of GMC1300‐1800 significantly decreases the coverage of sulfonic acid groups on Pt NPs, leading to the highest peak power density in the single‐cell test. Density functional theory calculations demonstrate the synergistic effect between graphitization and mesoporosity on enhancing the accessibility and durability of the catalysts.

Construction of structurally engineered NiCo2O4 nanostructures as a bifunctional electrocatalyst for high-performance overall water splitting

The development of low-cost and highly efficient bifunctional electrocatalysts for overall water splitting is a challenging but urgent goal. Herein, nickel cobaltite (NiCo2O4) with different morphologies was developed for electrocatalytic overall water splitting. Encouragingly, the NiCo2O4 nanoneedle arrays required competitive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 106 and 310 mV to achieve a density of 10 mA cm−2 (j10) in KOH media, respectively. Furthermore, the as-made nanoneedle electrocatalyst employed as both anode and cathode, which displayed a low voltage of 1.67 Vto attain j10, with satisfactory durability for 50 h. The nanoneedle morphology not only improves the electrochemical active surface area, but also helpful to boost the charge transfer ability of NiCo2O4 and control the adsorption of reaction intermediates in water splitting. These results demonstrate the feasibility of the NiCo2O4 nanostructure by altering the active sites using morphology to develop the electrocatalytic activity of the materials.

Durability Investigation of Low Pt-Loaded PEM Fuel Cells with Different Catalyst Layer Morphologies

This study investigates the durability of proton exchange membrane fuel cells against the Pt-dissolution degradation mechanism using a triangular accelerated stress test (AST) within the voltage range of 0.6-1 V. The electrochemical active surface area and polarization curves are reported throughout the AST for three different catalyst layers (CL), all featuring 0.1 mg/cm2 Pt loading but with different morphologies, which include the Pt/C weight percentages, dilution ratio, and thickness. In addition, a numerical model is employed to simulate the electrochemical performance of these samples at the beginning and end of life, considering the variations in the oxygen transport resistances and catalyst structure.

Bifunctional Strontium Cobalt Molybdenum Oxide (Sr2CoMoO6) Perovskite as an Efficient Catalyst for Electrochemical Water Splitting Reactions in Alkaline Media

Developing earth‐abundant low‐cost electrocatalysts is of prime research interest towards the need for clean energy technology, such as water‐splitting reactions. Herein, we have explored the electrocatalytic activity of the double perovskite‐based strontium cobalt molybdenum oxide (SCMO) towards water‐splitting reactions, both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Prepared by scalable autocombustion synthesis, the as‐synthesised bulk SCMO perovskite exhibited impressive electrocatalytic performance attributed to its substantial electrochemical active surface area. For the OER, it exhibited an overpotential of 350 mV with a Tafel slope value of 76 mV/dec. Concurrently, it showed proficient activity in the HER, revealing an overpotential of 270 mV and a Tafel slope of 112 mV/dec. Further, this perovskite material was stable during continuous electrocatalysis over a 24 h period with a negligible increase in observed overpotential value. The electronic density of states confirmed that the Co plays a pivotal role in enhancing electrocatalytic activities. This is achieved by a substantial reduction in the band gap and enhancement of the d‐band centre to an optimal level, rendering the system more favourable for electrocatalytic reactions. Our study contributes insights to the advancement of the design and utilization of perovskite‐based catalysts in the realm of sustainable energy technologies.

Gold nanodendrites enriched with gold nanoclusters on carbon-fiber as flexible acetaminophen sensor for clinical diagnostics

In this work, we demonstrate a flexible acetaminophen (APAP) microsensor based on gold dendrites decorated with gold nanoclusters on flexible carbon fiber (AuDS-AuNC|FCF) microelectrodes. The AuDS-AuNC|FCF microelectrodes are fabricated with a facile and single-step electrochemical strategy for electrocatalytic oxidation and sensing acetaminophen in a 0.1 M phosphate buffer (PB) (pH ∼7.4) solution. The as-developed AuDS-AuNC|FCF microsensors demonstrate excellent electrocatalytic oxidation of acetaminophen with a low oxidation potential of ∼0.54 V (vs. Ag/AgCl) and high catalytic current of ∼1.33 μA. This is because they have a lot of active sites, a large quantity of electrochemical active surface area (ECSA), and gold nanoclusters that are spread out homogeneously. The AuDS-AuNC|FCF microsensors exhibit fast sensing response time of ∼5.0 s, low experimental detection limit of ∼5.0 nM, high sensitivity of ∼0.375 ± 0.017 mA μM−1 cm−2 with a broad linear range of 5.0 nm–500.0 mM, good reproducibility, and possessed a robust anti-interference ability against sensing acetaminophen in the presence of potential interferences such as ascorbic acid, uric acid, adenine, guanine, glucose, etc. Notably, the present microsensor platform based on AuDS-AuNC|FCF microelectrodes is successfully tested for sensing acetaminophen in practical human serum samples, demonstrating its practicability in clinical diagnostics.

Activating Inert Perovskite Oxides for CO2 Electroreduction via Slight Cu2+ Doping in B-Sites.

Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x=0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x=0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.

Phase Engineering of High‐Entropy Alloy for Enhanced Electrocatalytic Nitrate Reduction to Ammonia

Directly electrochemical conversion of nitrate (NO3−) is an efficient and environmentally friendly technology for ammonia (NH3) production but is challenged by highly selective electrocatalysts. High‐entropy alloys (HEAs) with unique properties are attractive materials in catalysis, particularly for multi‐step reactions. Herein, we first reported the application of HEA (FeCoNiAlTi) for electrocatalytic NO3− reduction to NH3 (NRA). The bulk HEA is active for NRA but limited by the unsatisfied NH3 yield of 0.36 mg h−1 cm−2 and Faradaic efficiency (FE) of 82.66%. Through an effective phase engineering strategy, uniform intermetallic nanoparticles are introduced on the bulk HEA to increase electrochemical active surface area and charge transfer efficiency.The resulting nanostructured HEA (n‐HEA) delivers enhanced electrochemical NRA performance in terms of NH3 yield (0.52 mg h−1 cm−2) and FE (95.23%). Further experimental and theoretical investigations reveal that the multi‐active sites (Fe, Co, and Ni) dominated electrocatalysis for NRA over the n‐HEA. Notably, the typical Co sites exhibit the lowest energy barrier for NRA with *NO + H+ + e− → *NOH as the rate‐determining step.

Phase Engineering of High-Entropy Alloy for Enhanced Electrocatalytic Nitrate Reduction to Ammonia.

Directly electrochemical conversion of nitrate (NO3-) is an efficient and environmentally friendly technology for ammonia (NH3) production but is challenged by highly selective electrocatalysts. High-entropy alloys (HEAs) with unique properties are attractive materials in catalysis, particularly for multi-step reactions. Herein, we first reported the application of HEA (FeCoNiAlTi) for electrocatalytic NO3- reduction to NH3 (NRA). The bulk HEA is active for NRA but limited by the unsatisfied NH3 yield of 0.36 mg h-1 cm-2 and Faradaic efficiency (FE) of 82.66%. Through an effective phase engineering strategy, uniform intermetallic nanoparticles are introduced on the bulk HEA to increase electrochemical active surface area and charge transfer efficiency.The resulting nanostructured HEA (n-HEA) delivers enhanced electrochemical NRA performance in terms of NH3 yield (0.52 mg h-1 cm-2) and FE (95.23%). Further experimental and theoretical investigations reveal that the multi-active sites (Fe, Co, and Ni) dominated electrocatalysis for NRA over the n-HEA. Notably, the typical Co sites exhibit the lowest energy barrier for NRA with *NO + H+ + e- → *NOH as the rate-determining step.

Tailoring the high-density active sites via metal-coordinated ionic liquid encapsulated trimetallic core-shell MOF-derived catalysts for superior ORR in flexible Al-air batteries

The attainment of practicality in flexible Al-air batteries is impeded by the need for efficient air cathodes. To address this challenge, we systematically engineered the trimetallic (ZnCoFe)NC catalyst with a unique morphology of nitrogen-doped carbon nanotubes (NCNTs) on the 3D polyhedral structure (IL-ZnCoFe@CNT/NC) as an effective cathode. The augmented growth of NCNT facilitated by the metal-coordinated ionic liquid enhances both the specific surface area and the electrochemically active surface area (ECSA). As a result, IL-ZnCoFe@CNT/NC material exhibits a higher onset (1.0 V vs RHE) and half-wave potential (E1/2 = 0.89 V vs. RHE) as well as low Tafel slope (61 mV/dec) and surpassed the bare MOF-derived catalysts and Pt/C. E1/2 decreased by only 7 mV after the stability test describes the durability and fast reaction kinetics in the ORR. Upon testing on flexible Al-air with IL-ZnCoFe@CNT/NC cathode catalysts, it exhibited an OCV of 1.49 V and a peak power density of 34.7 mW cm−2 with 1.3 times higher power performance than the commercial Pt/C along with 3 times longevity than bare catalysts. Additionally, the Density-functional theory (DFT) calculations provide rational evidence that the IL-ZnCoFe@CNT/NC catalyst has an upshifted d-band center, which, in turn, enhances the adsorption of reaction intermediates, making the catalyst highly promising towards ORR.

Preparation of Oxygen Reduction Catalyst Electrodes by Electrochemical Acidification and Synergistic Electrodeposition

A proton exchange membrane fuel cell (PEMFC) is an efficient and environmentally friendly power production technology that uses hydrogen energy. The cathodic oxygen reduction electrode is a critical component in the development of PEMFC. Most techniques deposit catalyst nanoparticles in areas that are inaccessible for catalytic processes, reducing platinum utilization. The substrate used in this study was carbon paper (CP) with a self-supporting structure. First, electrochemical acidification technology was employed to modify the CP’s surface, followed by nanoparticle manufacturing and fixation on the CP in a single step by electrodeposition. The Pt/C0.5V2.24CP catalyst electrode demonstrated high-quality activity in the oxygen reduction reaction (ORR), with a homogeneous particle dispersion and particle size of around 50 nm. The mass activity and electrochemical active surface area (ECSA) of the Pt/C0.5V2.24CP catalyst electrode were 1.74 and 3.98 times higher than those of the Pt/C/CP-1 electrodes made with commercial catalysts, respectively. After 5000 cycles of accelerated durability testing (ADT), the mass activity and ECSA were 1.28 times and 6.16 times more than Pt/C/CP-1. This paper successfully proved the viability of electrodepositing Pt nanoparticles on CP following acidification, and that the electrochemical acidification methods have a positive influence on improving electrode ORR activity.

Experimental investigation of degradation mechanism in proton exchange membrane water electrolyzer under prolonged and severe bubble accumulation condition

Proton exchange membrane water electrolyzer (PEMWE) exhibits significant potential as a technology for hydrogen production driven by sustainable energy sources. In this study, the performance degradation characteristics of PEMWE under severe bubble accumulation condition lasting 100 h were investigated through in-situ and ex-situ characterization techniques. The results show that an increasing performance disparity with higher voltage, notably at lower temperatures, reaching a 58.2 % current density degradation rate at 50 °C and 2.0 V. Electrochemical impedance spectroscopy (EIS) analysis suggests that electrolyzer performance degradation is mainly due to increased charge transfer impedance, especially at the anode. In addition, the degraded electrolyzer exhibits a significant delay in reaching a stable current density during the abrupt voltage loading process, and its Tafel slope and electrochemically active surface area (ECSA) increased and decreased by 12.8 % and 13.5 %, respectively. Based on scanning electron microscopy (SEM) images, post-experiment analysis reveals pronounced thinning and noticeable cracks in both cathode and anode catalyst layers near the outlet, particularly on the anode side. Additionally, energy dispersive spectroscopy (EDS) mappings and transmission electron microscopy (TEM) images confirm substantial Pt/C and IrO2 catalyst particle dissolution, migration, and agglomeration. The findings of this study contribute to enhancing understanding of the performance degradation mechanisms in PEMWE.

Co3O4 derived ZnO: An effective electrocatalyst for oxygen evolution reaction in alkaline media

The growing accessibility of hydrogen and renewable energy sources has led to a rising significance of cobalt oxide (Co3O4)-based electrocatalysts in the context of effective electrochemical water splitting. Among two-half cell reactions, oxygen evolution reaction (OER) is more complicated and sluggish in behaviour. We present a composite material based on cobalt oxide-derived zinc oxide (Co3O4@ZnO) prepared through a wet chemical technique to overcome this challenge. The as-prepared materials are analyzed for crystallinity, morphology, and chemical bonding through X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), high resolution transmission electron spectroscopy (HRTEM), and Fourier transform infrared (FTIR) spectroscopy, respectively. The optimized electrocatalyst reveals higher electrochemical performance for OER with an overpotential value of 262 mV at 10 mA/cm2 current density, Tafel slope value of 59 mV/dec, and charge transfer resistance (Rct) of 72 Ω. Moreover, the electrochemical active surface area (ECSA) is calculated as 320 cm2. Notably, the desired electrocatalyst shows the stability of 50 h at 10 and 20 mA/cm2 current densities. The as-prepared catalyst (Co3O4@ZnO) with effective electrochemical features can be a potential candidate for energy conversion applications toward a sustainable society.

Benchmarking the Intrinsic Activity of Transition Metal Oxides for the Oxygen Evolution Reaction with Advanced Nanoelectrodes

AbstractThe intrinsic activity assessment of transition metal oxides (TMOs) as key electrocatalysts for the oxygen evolution reaction (OER) has not been standardized due to uncertainties regarding their structure and composition, difficulties in accurately measuring their electrochemically active surface area (ECSA), and deficiencies in mass‐transfer (MT) rates in conventional measurements. To address these issues, we utilized an electrodeposition‐thermal annealing method to precisely synthesize single‐particle TMOs with well‐defined structure and composition. Concurrently, we engineered low roughness, spherical surfaces for individual particles, enabling precise measurement of their ECSA. Furthermore, by constructing a conductor‐core semiconductor‐shell structure, we evaluated the inherent OER activity of perovskite‐type semiconductor materials, broadening the scope beyond just conductive TMOs. Finally, using single‐particle nanoelectrode technique, we systematically measured individual TMO particles of various sizes for OER, overcoming MT limitations seen in conventional approaches. These improvements have led us to propose a precise and reliable approach to evaluating the intrinsic activity of TMOs, not only validating the accuracy of theoretical calculations but also revealing a strong correlation of OER activity on the melting point of TMOs. This discovery holds significant importance for future high‐throughput material research and applications, offering valuable insights in electrocatalysis.

Benchmarking the Intrinsic Activity of Transition Metal Oxides for the Oxygen Evolution Reaction with Advanced Nanoelectrodes.

The intrinsic activity assessment of transition metal oxides (TMOs) as key electrocatalysts for the oxygen evolution reaction (OER) has not been standardized due to uncertainties regarding their structure and composition, difficulties in accurately measuring their electrochemically active surface area (ECSA), and deficiencies in mass-transfer (MT) rates in conventional measurements. To address these issues, we utilized an electrodeposition-thermal annealing method to precisely synthesize single-particle TMOs with well-defined structure and composition. Concurrently, we engineered low roughness, spherical surfaces for individual particles, enabling precise measurement of their ECSA. Furthermore, by constructing a conductor-core semiconductor-shell structure, we evaluated the inherent OER activity of perovskite-type semiconductor materials, broadening the scope beyond just conductive TMOs. Finally, using single-particle nanoelectrode technique, we systematically measured individual TMO particles of various sizes for OER, overcoming MT limitations seen in conventional approaches. These improvements have led us to propose a precise and reliable approach to evaluating the intrinsic activity of TMOs, not only validating the accuracy of theoretical calculations but also revealing a strong correlation of OER activity on the melting point of TMOs. This discovery holds significant importance for future high-throughput material research and applications, offering valuable insights in electrocatalysis.

Intrinsically stretchable jellyfish-like gold nanowires film as multifunctional wearable chemical and physical sensors

We report on an intrinsically stretchable jellyfish-like gold nanowires film as a multifunctional wearable platform that can detect both chemical and physical biometrics. The film inherently exhibits multifunctionality, serving directly as an electrochemical electrode, strain sensor, temperature sensor, pressure sensor, and noncontact humidity sensor without the need of any additional materials. Our results highlight the excellent electrochemical properties, evidenced by a large electrochemical active surface area (EASA) of approximately 22.39 cm2 and the ability to withstand significant strain values up to 70 %. Leveraging these attributes, a stretchable electrochemical glucose biosensor was further designed with high sensitivity (45.40μA·mM−1·cm−2) and low limit of detection (10 μM). In addition, its sensing applications in strain, temperature, pressure and noncontact humidity were systematically explored. Impressively, the gold film is capable of monitoring multiple human motions and physiological signals, including joints bending, pulse motions, throat motions (e.g., drinking, speaking, swallowing and pronunciation recognition) and breathing. Furthermore, the film exhibited great versatility by integrating with 3D printing hydrogels, enabling customized patterning. The results demonstrate that our gold nanowires coating approach represent a new route to design multimodal soft wearable platforms for applications in personalized medicine and next-generation healthcare systems.

Controllable boosting activity on Co4N by Fe substitution for oxygen evolution reaction and efficient 5-hydroxymethylfurfural oxidation

The design of transition metal nitrides with excellent oxygen evolution reaction and 5-hydroxymethylfurfural oxidation reaction (HMFOR) is of great significance to achieve the goal of "carbon peaking and carbon neutrality". Herein, Fe-doped bimetallic nitride FexCo1-x)4N was prepared by a simple electron regulation strategy. The introduction of Fe changes the electronic structure of Co and optimizes the adsorption energies of *OH, reduces the potential barrier for the generation of *OOH as a potential-determining step and thus increases the intrinsic OER activity of Co4N. In addition, Fe substitution of some of the Co atoms gives (FexCo1-x)4N a higher electrochemical active surface area, which accelerates the electron transfer efficiency and improves the electrical conductivity. The overpotential for (FexCo1-x)4N-0.9 to reach a current density of 10 mA cm−2 in 1 M KOH is only 271 mV. When in 1 M KOH + 50 mM HMF condition, (FexCo1-x)4N-0.9 requires only 1.37 V to reach a current density of 10 mA cm−2. This work provides practical guidance for developing bifunctional transition metal electrocatalysts with excellent OER and HMFOR activity.

Electrocatalytic properties of Ni–Cu structures fabricated by electrodeposition of Cu on Ni cones

Ni–Cu alloys are a suitable candidate as a catalyst in Hydrogen Evolution Reaction due to their catalytic performance and good stability. To enhance this activity more, the active surface area of the material should be enhanced. It is commonly achieved by the synthesis of metals and alloys in the form of nanostructures. In this work, Ni cones fabricated by the one-step method were applied as a substrate for the deposition of thin Cu layers. Then, these materials were annealed in an ambient atmosphere to obtain Ni–Cu structures. The investigation of changes in morphology and chemical composition, as well as roughness and wettability before and after the annealing process was performed. Moreover, the measurements of catalytic properties were carried out in 1 M NaOH. The values of the Tafel slope and the electrochemical active surface area were studied. The proposed method can be successfully applied to fabricate structures of other alloys for the desired properties.