Electrochemical Active Surface Area Research Articles

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.

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.

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.

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 solid-state 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 vs RHE after the stability test describes the durability and fast reaction kinetics in the ORR. Upon testing on flexible solid-state 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 catalyst. 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.

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.

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.

Influence Factors of Platinum Dissolution in Proton Exchange Membrane Fuel Cells: A Sensitivity Study

Abstract Polymer electrolyte fuel cells for heavy-duty applications require lifetimes beyond 30,000 hours, which poses a durability challenge. In this study, we investigated the influence of various factors on loss of electrochemically active surface area (ECSA) in the cathode, which is a major limiting factor. We derive a parameter range from simulated drive cycles showing that the voltage ranges between 0.70 and 0.85 V and that the cells are in idle state at upper potential limit (UPL) most of the time. We evaluate the influence and interaction of UPL, lower potential limit (LPL), temperature, relative humidity, and cycle time on ECSA and performance at four different operating conditions after 10,000 potential cycles based on 25 experiments. The results indicate that UPL and the hold time at UPL have the strongest impact on degradation, while LPL has a small impact, which does not increase below the potential of full platinum reduction (0.55 V) or hold times longer than 2 seconds. Furthermore, the interaction of humidity with other factors becomes significant for long experiment times. In summary, the findings of this work can serve as guidelines for minimizing ECSA loss, e.g. by keeping the fuel cell in a benign operation regime via systems control

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.

Electrocatalytic sensing of propyl gallate in real-time food samples using a synergistic Sm-MOF@GCN composite modified glassy carbon electrode

A novel electrochemical sensor has been developed using the sonochemically synthesized samarium metal–organic framework (Sm-MOF) and the graphitic carbon nitride (GCN) composite for the selective determination of propyl gallate (PG). The as-synthesized Sm-MOF@GCN composite was characterized by XRD, XPS, and FESEM. The morphological studies of the prepared Sm-MOF@GCN composite revealed the bar-shaped Sm-MOF and porous sheet-like morphology of GCN. The combined effect of the Sm-MOF and GCN enhance the current density response and lowers the oxidation potential, which was beneficial for the electrochemical sensing of PG. Moreover, the high electrochemical active surface area (EASA) (0.0649 cm2) and the rate constant value (Ko) of 1.44x10-5 cm s−1 confirm the faster electron transfer kinetics at the interface of Sm-MOF@GCN composite. However, the developed Sm-MOF@GCN composite possesses linear range from 0.02 to 60 µM with a nanomolar detection level (2.05 nM), high sensitivity (0.1914 μA μM−1 cm−2), excellent reproducibility, repeatability, and stability for up to 30 days towards the PG detection. Finally, the Sm-MOF@GCN composite-modified electrocatalyst was utilized for the quantification of PG in foodstuffs such as instant noodles, cookies, cakes, and oils. The result of the study, the Sm-MOF@GCN composite displayed good recovery results, making it a promising candidate for detecting PG in real-world samples in view of its binder-free approach and facile fabrication process.

Green and sustainable use of macadamia nuts as support material in Pt-based direct methanol fuel cells

The successful commercialization of direct methanol fuel cells (DMFCs) is hindered by inadequate methanol oxidation activity and anode catalyst longevity. Efficient and cost-effective electrode materials are imperative in the widespread use of DMFCs. While Platinum (Pt) remains the primary component of anodic methanol oxidation reaction (MOR) electrocatalysts, its utilization alone in DMFC systems is limited due to carbon monoxide (CO) poisoning, instability, methanol crossover, and high cost. These limitations impede the economic feasibility of Pt as an electrocatalyst. Herein, we present the use of powdered activated carbon (PAC) and granular activated carbon (GAC), both sourced from macadamia nut shells (MNS), a type of biomass. These bio-based carbon materials are integrated into hybrid supports with reduced graphene oxide (rGO), aiming to enhance the performance and reduce the production cost of the Pt electrocatalyst. Electrochemical and physicochemical characterizations of the synthesized catalysts, including Pt-rGO/PAC-1:1, Pt-rGO/PAC-1:2, Pt-rGO/GAC-1:1, and Pt-rGO/GAC-1:2, were conducted. X-ray diffraction analysis revealed crystallite sizes ranging from 1.18 nm to 1.68 nm. High-resolution transmission electron microscopy (HRTEM) images with average particle sizes ranging from 1.91 nm to 2.72 nm demonstrated spherical dispersion of Pt nanoparticles with some agglomeration across all catalysts. The electrochemical active surface area (ECSA) was determined, with Pt-rGO/GAC-1:1 exhibiting the highest ECSA of 73.53 m2 g−1. Despite its high ECSA, Pt-rGO/GAC-1:1 displayed the lowest methanol oxidation reaction (MOR) current density, indicating active sites with poor catalytic efficiency. Pt-rGO/PAC-1:1 and Pt-rGO/PAC-1:2 exhibited the highest MOR current densities of 0.77 mA*cm−2 and 0.74 mA*cm−2, respectively. Moreover, Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 demonstrated superior electrocatalytic mass (specific) activities of 7.55 mA/mg (0.025 mA*cm−2) and 7.25 mA/mg (0.021 mA*cm−2), respectively. Chronoamperometry tests revealed Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 as the most stable catalysts. Additionally, they exhibited the lowest charge transfer resistances and highest MOR current densities after durability tests, highlighting their potential for DMFC applications. The synthesized Pt supported on PACs hybrids demonstrated remarkable catalytic performance, stability, and CO tolerance, highlighting their potential for enhancing DMFC efficiency.

Cu2MoS4 Nanocatalyst-based Electrochemical Sensor for Ofloxacin Electro-Oxidation: Delineating the Combined Roles of Crystallinity and Morphology on the Analytical Performance.

In this study, we demonstrate the influence of crystallinity and morphology on the analytical performance of various Cu2MoS4 (CMS) nanocatalysts-based electrochemical sensors for the high-efficiency detection of Ofloxacin (OFX) antibiotic. The electrochemical kinetics parameters including peak current response (ΔIp), peak-to-peak separation (ΔEp), electrochemically active surface area (ECSA), electron-transfer resistance (Rct), were obtained through the electrochemical analyses, which indicate the single-crystalline nature of CMS nanomaterials (NMs) is beneficial for enhanced electron-transfer kinetics. The morphological features and the electrochemical results for OFX detection substantiate that by tuning the tube-like to plate-like structures of the CMS NMs, it might noticeably enhance multiple adsorption sites and more intrinsic active catalytic sites due to the diffusion of analytes into the interstitial spaces between CMS nanoplates. As results, highly single-crystalline and plate-shaped morphology structures of CMS NMs would significantly enhance the electrocatalytic OFX oxidation in terms of onset potential (Eonset), Tafel slope, catalytic rate constant (kcat), and adsorption capacity (Γ). The CMS NMs-based electrochemical sensing platform showed excellent analytical performance toward the OFX detection with two ultra-wide linear detection concentration ranges from 0.25 - 100 and 100 - 1000 μM, a low detection limit of 0.058 μM, and an excellent electrochemical sensitivity (0.743 µA µM-1 cm-2).

Chrysanthemum‐Flowers‐Like Bimetal Oxide Based Electrocatalyst for Methanol Oxidation Reaction

Transition metal oxides have garnered attention for the methanol electro‐oxidation reaction owing to their easy availability, high catalytic applicability, and multiple oxidation capabilities. Bimetal‐based catalysts further enhance the performance of the methanol oxidation reaction. In this context, a chrysanthemum‐flower‐like MoO2/WO3 is synthesized through a solvothermal and annealing strategy. The morphology attests to the rough surface and pores in the catalyst, augmenting its surface area for reactions and enhancing catalytic applicability. Electrochemical oxidation of methanol yields an optimal current density of 0.99 mA cm−2 and 2.07 mA mg−1 at a potential of 0.57 V versus Ag/AgCl. The catalyst exhibits a remarkably low Tafel slope of 37.45 mV dec−1, affirming its rapid reaction kinetics. Electrochemical impedance spectroscopy (EIS) reveals an equivalent electronic circuit of R(Q(R(QR)Q(RW))), confirming low charge transfer resistance (Rct) and diffusion‐controlled kinetics attributable to the pores in the sample. The sample also demonstrates an electrochemically active surface area (ECSA) value equal to 0.122 mF cm−2 and long‐term stability over continuous 5000 s, exhibiting no change and high resistance to CO poisoning. All these characterizations and obtained results collectively affirm that the chrysanthemum‐flower‐like MoO2/WO3 serves as a highly suitable electrocatalyst for the electrochemical oxidation of methanol.

Insights into synergetic modulation of nickel sites over graphene by introducing tungsten and light for efficient methanol electrooxidation

Cut-lost, highly active and stable (photo-)electrocatalysts are earnestly expected to overcome high energy obstacles in methanol oxidation reaction (MOR). A hybrid of NiW/graphene (NiW/G) is prepared by a simple self-designed electrosynthesis method. During the process of electrosynthesis, exfoliation of bulky graphite into graphene and generation of multivalent NiW bimetal precursor are both achieved. This obtained composite displays superior photoelectrocatalytic performance towards MOR. As for NiW/G-light, its area activity (peak current) and mass activity (peak current) are up to 343.4 mA cm−2 and 5960.7 mA mg−1 respectively, much higher than NiW/G, Ni/G and W/G. Operando electrochemical impedance spectroscopy, in-situ Fourier transform infrared spectroscopy and other ex-situ techniques uncover that the excellent MOR performance for NiW/G-light results from synergetic modulation of nickel sites by introducing tungsten and light, which provides desired adsorption behavior and high electrochemical active surface area. It’s found that introduction of W component promotes the formation of W-O-Ni(Ni3+) species, supporting more strong adsorption sites for methanol. This results in new reaction path between adsorbed methanol and OH* for producing formic acid. With application of light, the photo-generated hole promotes oxidation of residual Ni2+ into Ni3+ species, which provides additional formed NiOOH sites for MOR. It’s concluded introduction of tungsten and light is efficient for greatly enhancing methanol electrooxidation. This work is highly instructive for application of self-designed electrosynthesis method to construct dimetal/graphene composite and photoelectric synergistic catalysis towards MOR.

The hierarchical dense structure induced high stability to NiCoB-based electrode for electrochemical energy storage

The construction of stable hierarchical surfaces through structural engineering is the key to improve reactive active sites and cycle stability to achieve high cycle performance of supercapacitors (SCs). In this work, the NiCo-LDH nanoflower as a structure guide agent was used to support NiCoB nanosheets to form a dense and stable hierarchical structure, thereby exposing more active sites and improving cycle stability. Due to the hierarchical stable surface structure, the NiCoB-0.3@NiCo-LDH-30 electrode has an excellent specific capacitance of 2710F g−1 at 1 A/g due to the excellent electrochemical active surface area (1259 mF cm−2), improving the OH– diffusion coefficient (2.4 × 10−9 cm2 s−1) and decreasing ionic diffusion barrier. After 5000 cycles, NiCoB-0.3@NiCo-LDH-30 electrode still has 92.6 % initial specific capacitance. In order to balance the energy density decrease caused by the capacitance imbalance between positive and negative electrodes, the cubed carbon (Co-C) derived from cobalt metal organic frameworks (Co-MOFs) as cathode with a good specific capacitance of 220F g−1 at 1 A/g is prepared. The assembled NiCoB-0.3@NiCo-LDH-30//Co-C hybrid SCs (HSCs), which are assembled with NiCoB-0.3@NiCo-LDH-30 electrode as anode and Co-C electrode as cathode, displays an energy density of 75 Wh kg−1 at a power density of 741 W kg−1.

CoFeBP Micro Flowers (MFs) for Highly Efficient Hydrogen Evolution Reaction and Oxygen Evolution Reaction Electrocatalysts.

Hydrogen is one of the most promising green energy alternatives due to its high gravimetric energy density, zero-carbon emissions, and other advantages. In this work, a CoFeBP micro-flower (MF) electrocatalyst is fabricated as an advanced water-splitting electrocatalyst by a hydrothermal approach for hydrogen production with the highly efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The fabrication process of the CoFeBP MF electrocatalyst is systematically optimized by thorough investigations on various hydrothermal synthesis and post-annealing parameters. The best optimized CoFeBP MF electrode demonstrates HER/OER overpotentials of 20 mV and 219 mV at 20 mA/cm2. The CoFeBP MFs also exhibit a low 2-electrode (2-E) cell voltage of 1.60 V at 50 mA/cm2, which is comparable to the benchmark electrodes of Pt/C and RuO2. The CoFeBP MFs demonstrate excellent 2-E stability of over 100 h operation under harsh industrial operational conditions at 60 °C in 6 M KOH at a high current density of 1000 mA/cm2. The flower-like morphology can offer a largely increased electrochemical active surface area (ECSA), and systematic post-annealing can lead to improved crystallinity in CoFeBP MFs.

Single‐Step Laser Irradiation for Synchronous Formation of Graphene‐Platinum Nanohybrids with Tunable Microstructures Toward High‐Performance Enzyme‐Free Glucose Sensors

AbstractManufacturing of metal‐decorated carbon electrodes as a critical component of enzyme‐free glucose sensors has become an advanced strategy for fast and accurate glucose monitoring. By selectively irradiating the pre‐prepared chloroplatinic acid/polyimide (H2PtCl6/PI) precursor with photothermal energy, a creatively synchronized laser processing protocol is developed for assembling integrated three‐electrode system with platinum nanoparticle decorated laser‐induced graphene (PtNP‐LIG). In addition to the swift manufacturing of designable structures, laser power and raw‐material dosage are systematically explored as two key parameters to understand the process‐regulated microstructure and electro‐catalytic performance. Notably, by discovering the tuning mechanism for optimizing laser power‐dependent specific surface area of graphene backbone from 81.61 to 197.53 m2 g−1 and for enhancing H2PtCl6 concentration dependent Pt content from 0.75% to 4.16%, the sensitivity of PtNP‐LIG sensors to glucose oxidation has dramatically improved from 203.14 to 959.07 µA mM−1 cm−2, following closely the adjustable discipline of electrochemically active surface area (ECSA) from 37.75 to 104.19 mm2. Along with rapid response time, low limit of detection, and broad linear range, the proposed protocol is highly beneficial for designing and manufacturing next‐generation wearable human‐health related devices.

Revealing the critical role of low voltage excursions in enhancing PEM fuel cell catalyst degradation by automotive hydrogen/air potential cycling experiments

The durability of Polymer Electrolyte Membrane Fuel Cells under dynamic operation still needs to be improved. To understand the automotive voltage cycling-induced catalyst degradation, the loss of the electrochemically active surface area (ECSA) is investigated through an experimental campaign on Membrane Electrode Assemblies. Ad-hoc hydrogen/air accelerated protocols were designed to evaluate the voltage profile impact in a range relevant for both automotive and heavy duty transport application (<0.90 V). Besides the well-known aging dependence on the upper potential limit, this work evidences the critical role of the short-stops, characterized by low voltage transients. Effort was spent in studying this procedure parameters (voltage level, duration, scan rate, humidification). The accelerated ECSA loss is due to Pt nanoparticles coarsening as proved by transmission electron microscopy and is suspected dominated by Pt cathodic dissolution, incentivized during excursions towards very low potentials (<0.4 V). These findings help the development of system mitigation strategies.