Times Higher Current Density Research Articles

(Invited) Boosting Oxygen Evolution Reaction by Stabilization of Ultrasmall Ruthenium Nanoclusters on Thiol-Functionalized Metal-Organic Framework

Rational designing of efficient nanocatalysts plays a crucial role in catalyzing kinetically sluggish reactions like Oxygen Evolution Reaction (OER). However, the uncontrolled nucleation and growth of nanostructures poses major effectiveness and economic challenges in the implementation and commercialization of noble metal-based electrocatalysts. Functionalized Metal-Organic Frameworks (MOFs) have the properties to stabilize such unstable nanoclusters in extremely small sizes by compensating for their high surface energy and Ostwald’s ripening effect. Here, we have reported the synthesis of ultrasmall Ruthenium nanoclusters stabilized through thiol-functionalized Ni-MOF (Ru@Ni-M-SH). The stabilization of ruthenium under reduced conditions on the MOF surface was facilitated by the lower electronegativity and increased orbital overlapping effect of sulfur, resulting in an average size of 1.5 nm. A perturbed electronic structure confirmed from XPS as well as XAS studies revealed the fundamental understanding behind electronic redistribution. Backed with such a favorable electronic structure, the catalytic OER activity for Ru@Ni-M-SH outperformed the state-of-the-art RuO2 with three times higher current density (242 mA/cm2) and 143 mV reduced overpotential. With 95% Faradaic efficiency, the Turnover Frequency (TOF) and Mass activity of Ru@Ni-M-SH were found to be several orders higher as compared to RuO2. Unlike other Ru-based catalysts, Ru@Ni-M-SH showed extremely high stability with over 24 h of chronoamperometry study. With thorough in-situ analysis providing information regarding catalytically active sites and intermediates, Ru@Ni-M-SH established itself as an economically sustainable OER electrocatalyst.

Atomic Layer Deposition of Cu Catalysts on Gas Diffusion Electrodes for Electrochemical CO2 Reduction

Electrochemical CO2 conversion is gaining attention as an important process for carbon fixation through the use of renewable electricity to address the climate change crisis. Copper is a unique single-element catalyst that can induce C-C coupling reactions to generate high-value-added compounds. The triple phase boundary has been successfully controlled at the catalyst interface using gas diffusion electrodes (GDEs) over the past few years, resulting in high C-C coupling performance. Therefore, methods to engineer the catalyst interface on the 3D structure of GDE are of significant importance. Generally, the catalyst on the GDE is introduced through physical vaper deposition (PVD) using sputtering or E-beam evaporation, or through solution methods such as spray coating and drop-casting of nano-particles. However, the porous and tortuous 3D structure of the GDE often result in limited conformality and difficulty in obtaining a uniform and controlled infiltration of the catalyst into the support structure.In this study, we synthesized Cu catalysts directly onto GDE surfaces using plasma-enhanced atomic layer deposition (PE-ALD), which allowed for precise tuning of the catalyst size and loading at the nanoscale [1]. The synthesized catalysts were confirmed to be polycrystalline Cu nanoparticles using grazing incidence X-ray diffraction. To demonstrate the advantages of the conformal and tunable control of PE-ALD deposition, we deposited the same areal mass loading of Cu catalyst onto the GDE substrates using PVD, and compared the CO2 reduction activity in an H-cell environment. The PE-ALD Cu catalyst showed more than 3 times higher current density than the PVD catalyst at the same electrode potential, a low (~10%) Faradaic efficiency (FE) for the hydrogen evolution reaction (HER), and greater than 75% FE for C-C coupling to form C2+ products including ethylene and ethanol, which is comparable to the highest performances reported to date for metallic Cu catalysts in a H-cell environment. Furthermore, stable operation was observed for a duration of 15 hours, with minimal changes in activity and selectivity. In conclusion, the introduction of catalysts using PE-ALD on GDE electrodes represents a powerful new synthesis method that can increase both C-C coupling performance and selectivity compared to PVD deposition, due to its adjustable Cu nanoparticle size and high conformality. Reference 1) J. D. Lenef, S.Y. Lee, K. M. Fuelling, K. E. Rivera Cruz, A. Prajapati, D. O. D. Cornejo, T. H. Cho, K. Sun, E. Alvarado, T. S. Arthur, C. A. Roberts, C. Hahn, C. C. L. McCrory, N. P. Dasgupta, Nano Lett. 23, 10779-10787 (2023)

Self-assembled Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O2-δ composite for solid oxide electrolysis cells

The anode is the key material that constrains the performance of solid oxide electrolysis cells (SOECs). Here, we have developed self-assembled Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O2-δ (SSC-SDC) composite by the co-synthesis strategy and studied its electrochemical performance as the anode for SOECs. The surface and interface properties of the self-assembled SSC-SDC composite were systematically studied. The SDC lattice expansion and the SSC lattice contraction of the SSC-SDC composite have been shown by XRD analysis, ascribed to the strong cation interdiffusion during the self-assembly process. The self-assembled SSC-SDC also exhibits superior oxygen evolution activity and displays a larger oxygen desorption peak than the physically mixed SSC&SDC. A higher proportion of adsorbed oxygen species on the surface of the self-assembled SSC-SDC than the physically mixed SSC&SDC also have been shown by XPS results. The cell with the self-assembled SSC-SDC as anode exhibits ca. 2.1 times higher current density than the physically mixed SSC&SDC as anode. Meanwhile, the polarization resistance of the cell with self-assembled SSC-SDC as the anode is 0.0957 Ω cm2, which is only 40 % of that observed in the cell where SSC and SDC are physically mixed as the anode. This novel self-assembly strategy shows great potential for preparing high-performance oxygen electrodes.

Hybrid 1D titanium oxide nanowire – Reduced graphene oxide nanocomposites as efficient catalyst support for PEMFC

With hydrogen being projected as the fuel of the future, proton exchange membrane fuel cells (PEMFC) have regained prominence as a zero-emission power source. Researchers are focusing on replacing the conventional carbon support used for the platinum catalysts with alternative materials to improve the durability of the electrocatalysts. Despite being a potential candidate, graphene-based materials have been limited by their lower limiting current density, possibly due to restacking of the graphene sheets. On this note, we introduced varying quantities of metal-oxide based 1D TiO2 nanowires to reduced graphene oxide (rGO) support and analysed their impact on the performance of the electrocatalyst. The optimized support with an initial content of 60 wt.% GO and 40 wt.% TiO2 exhibited higher mass transfer limiting current density, after Pt incorporation (Pt/TiO2-rGO), in comparison to the other composites. The catalyst showed higher retention in electrochemical surface area (1.42 times) and mass activity (1.48 times) compared to the commercial Pt/C after an accelerated durability test. Polarization studies carried out in a 25 cm2 fuel cell fixture exhibited a peak power density close to 720 mW cm−2 and almost two times higher current density (at 0.6 V) than the catalyst without TiO2. These results reaffirm the role of TiO2 in overcoming the limitations of graphene-based support.

Unveiling the resistance component on fuel cell electrodes by ionic liquid adsorbed PtCo/C catalyst through distribution of relaxation time

A majority of studies focus on developing oxygen reduction reaction (ORR) catalysts and cathode configurations to enhance the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs). In this study, resistance analyses of the membrane electrode assembly (MEA) are conducted to elaborate on the performance and durability improvements induced by the adsorption of [MTBD][beti] ionic liquid (IL) on the commercial PtCo/C catalyst. The morphological changes caused by IL adsorption are observed on micro and macro scales via physicochemical methods. From the half-cell measurement, when the 4 wt% IL was adsorbed, a 15 mV improvement in ORR activity occurred, and as the adsorption amount increased, the activity decreased. The MEA using 8 wt% IL adsorbed catalyst outperforms 1.7 times higher current density at 0.8 V and 40 % lower charge transfer resistance. Distribution of relaxation time resistance analysis reveals that oxygen mass transfer resistance (Rmass), ORR charge transfer resistance (RORR), and proton charge transfer resistance (Rproton) decrease due to IL adsorption. During accelerated durability tests, IL 8 % MEA showed a 58 % increase in durability, and a lower degradation of RORR and Rproton encouraged improved durability. The resistance analyses in this study contribute to identifying the factors responsible for the performance and durability enhancement of PEMFC.

Straightforward electrochemical synthesis of a Co3O4 nanopetal/ZnO nanoplate p-n junction for photoelectrochemical water splitting.

Hydrogen production through photoelectrochemical (PEC) reactions is an innovative and promising approach to producing clean energy. The PEC working electrode of a Co3O4/ZnO-based p-n heterojunction was prepared by a straightforward electrochemical deposition with different deposition times onto an FTO (Fluorine-doped Tin Oxide) glass substrate. The successful synthesis of the materials was confirmed through analysis using XRD, FTIR, SEM-EDX, DRS, and PL techniques. Mott-Schottky plots and some characterization studies also checked the determination of the formation of the p-n junction. Co3O4/ZnO/FTO with a Co3O4 deposition time of 2 minutes exhibited the lowest onset potential of 0.82 V and the lowest overpotential of 470 mV at a current density of 10 mA cm -2. Furthermore, the photo-conversion efficiency of the Co3O4/ZnO/FTO sample showed 1.4 times higher current density than the ZnO/FTO sample. A mechanism is also proposed to enhance the Co3O4/ZnO/FTO electrode photo-electrocatalytic activity involved in the water-splitting reaction. The Co3O4/ZnO/FTO electrode shows significant potential as a promising PEC electrode to produce hydrogen.

Environmentally friendly PtNiCo nanocatalysts enhanced with multi-walled carbon nanotubes for sustainable methanol oxidation in an alkaline medium.

In this study, trimetallic PtNiCo/MWCNT and PtNiCo catalysts were synthesized using a microwave method to reduce the amount of precious Pt. The prepared catalysts were characterized using XRD, TEM, and EDX mapping and their electrochemical performances for methanol oxidation were investigated. The results showed that the MWCNT-supported catalyst showed 2.42 times higher electrochemical activity than the PtNiCo catalyst with a peak current density of 283.14 mA cm-2 at -0.2 V potential. Moreover, in long-term stability tests, it exhibited high stability and 4.97 times higher current density at the end of 3600 s. The results showed that the MWCNT-supported catalyst offered improved electron transfer, 4.7 times higher surface area, and resistance to CO poisoning. These performance improvements due to the trimetallic structure are mostly thought to help accelerate the dehydrogenation of methanol. This study contains important findings for future functional catalyst design in the fields of catalysis and energy conversion.

Synergistic Integration of Zr-MOF (UiO-66) and Bi Electrocatalysts for Enhanced CO2 Conversion to Formate

The utilization of renewable energy-driven CO2 conversion technology has garnered considerable attention as a potential remedy for both the energy crisis and climate change. Among various methods, the electrocatalytic CO2 reduction reaction (CO2RR) has received particular focus due to its mild reaction conditions and its ability to produce various valuable products. Specifically, formic acid holds great promise for CO2 electrolysis due to its potential for energy storage and transportation, as well as its commercial viability as indicated by techno-economic assessments. Bi, In, and Sn are several metal catalysts that have been reported for formic acid production, with Bi catalysts demonstrating favorable properties in terms of both cost-effectiveness and selective production of formic acid. However, despite efforts to enhance the intrinsic catalytic activity of Bi through methods such as nanostructuring and alloying, it has yet to achieve the desired level of performance. In light of recent findings by Nam et al. on the ability of a metal-organic framework (MOF) to regulate reaction intermediates for Ag catalyst, resulting in higher CO production, we draw inspiration from MOF's versatility and demonstrate the successful coupling of Bi with UiO-66, a Zr-MOF, to achieve higher CO2 reduction rates and thus increase formic acid production [1]. We synthesized MOF materials, UiO-66 and NH2-functionalized UiO-66 (UiO-66-NH2), and deposited Bi catalysts on the MOF structures using the NaBH4 reduction method, resulting in Bi/UiO-66 and Bi/UiO-66-NH2 samples. To compare the catalytic activity, we also synthesized Bi particle samples using the same method (Bi). Prior to CO2 reduction examination, all electrocatalysts were pre-treated in a 1.0 M KOH solution for 5 minutes, and then CO2 electrolysis was performed in a flow-cell reactor. Among the synthesized samples, Bi/UiO-66 demonstrated excellent CO2 reduction properties, exhibiting about 5 times higher current density (-220 mA/cm2) at an applied potential of -0.7 V vs. the reversible hydrogen electrode (RHE) than Bi alone (-44 mA/cm2), despite the identical electrochemically active surface area (ECSA) for both samples. On the other hand, Bi/UiO-66-NH2 showed an almost identical ECSA-normalized current density compared to Bi/UiO-66, indicating the negligible effect of NH2 functionalization on UiO-66 for CO2RR. Nevertheless, it is evident that the utilization of Zr-MOF (UiO-66) is beneficial in increasing the CO2 conversion rate of metallic Bi catalyst. To comprehend the reason behind the superior catalytic activity exhibited by the Bi/UiO-66 sample, we conducted various characterizations, such as SEM, TEM, FTIR, Raman, and XPS. Our results revealed that the structural evolution of UiO-66 occurs by the formation of carbonate-coordinated Zr-hydroxide during CO2 electrolysis, contributing to the high CO2 reduction current density. Moreover, the disappearance of the carbonate-relevant peak in the C 1s from XPS analysis after the decline in catalytic activity suggests that the carbonate species formed at Zr-MOF site, which is the captured form of CO2 molecules, play a crucial role in efficient CO2 capture and conversion. These findings suggest that Zr-MOF can be used for CO2 capture and conversion with high efficiency.[1] Nam et al., J. Am. Chem. Soc. 2020, 142, 51, 21513–21521.

Electrochemical Activation of Atomic-Layer-Deposited Nickel Oxide for Water Oxidation.

NiO-based electrocatalysts, known for their high activity, stability, and low cost in alkaline media, are recognized as promising candidates for the oxygen evolution reaction (OER). In parallel, atomic layer deposition (ALD) is actively researched for its ability to provide precise control over the synthesis of ultrathin electrocatalytic films, including film thickness, conformality, and chemical composition. This study examines how NiO bulk and surface properties affect the electrocatalytic performance for the OER while focusing on the prolonged electrochemical activation process. Two ALD methods, namely, plasma-assisted and thermal ALD, are employed as tools to deposit NiO films. Cyclic voltammetry analysis of ∼10 nm films in 1.0 M KOH solution reveals a multistep electrochemical activation process accompanied by phase transformation and delamination of activated nanostructures. The plasma-assisted ALD NiO film exhibits three times higher current density at 1.8 V vs RHE than its thermal ALD counterpart due to enhanced β-NiOOH formation during activation, thereby improving the OER activity. Additionally, the rougher surface formed during activation enhanced the overall catalytic activity of the films. The goal is to unravel the relationship between material properties and the performance of the resulting OER, specifically focusing on how the design of the material by ALD can lead to the enhancement of its electrocatalytic performance.

Methanol assisted water electrooxidation on noble metal free perovskite: RRDE insight into the catalyst’s behaviour

In this work, we have hypothesized that noble metal-free perovskites are an essential class of oxygen evolution reaction (OER) catalysts in an alkaline medium and thus, they are a suitable candidate for the assisted water oxidation catalysts. Herein, we demonstrate that the origin of the methanol-assisted OER activity at near thermodynamic potential on perovskite electrode arises due to the involvement of additional hydroxyls as a result of dissociative chemisorption of methanol. When the perovskite electrode is screened for methanol electrooxidation reaction in 0.5 M KOH + 0.5 M methanol electrolyte, it delivers a two times higher current density. This imparts an 82 % increase in the evolution of oxygen gas moles with complete oxidation of methanol to carbon dioxide. Along with the electrochemical characterization to understand the electrocatalyst property, Rotating ring disk electrode (RRDE) technique is explored for the first time in literature to validate the catalyst’s involvement during OER. RRDE is effective in understanding the lattice oxygen behaviour and methanol-assisted water electrooxidation during OER. Our results suggest new insights and ideas towards the oxygen evolution reaction process and the mechanistic insight into the elevated OER due to assisted methanol electrooxidation.

Fabrication of nanofibrous PbO2 electrode embedded with Pt for decomposition of organic chelating agents

A new fabrication method of nanofibrous metal oxide electrode comprising Pt nanofiber (Pt–NF) covered with PbO2 on a Ti substrate was proposed. Pt–NF was obtained by performing sputtering deposition of Pt on the surface of electrospun poly(vinyl alcohol) (PVA) nanofiber on a Ti substrate, in which PVA was then removed by calcination (Ti/Pt–NF). Subsequently, by introducing PbO2 to the Ti/Pt–NF using the electrodeposition method, a nanofibrous Ti/Pt–NF/PbO2 electrode was finally obtained. Because the Ti substrate was covered by nanofibrous Pt, it had no environmental exposure and thus, was not oxidized during calcination. The crystal structure of the PbO2 mainly consisted of β-form rather than α-form; the β-form was suitable for electrochemical decomposition and remained stable even after 20 h of use. The nanofibrous Ti/Pt–NF/PbO2 electrodes showed 10% lower anode potential, 1.6 times higher current density at water decomposition potential, lower electrical resistance in the ion charge transfer resistance, and 2.27 times higher electrochemically active surface area than those of a planar-type Ti/Pt/PbO2 electrode, and demonstrated excellent electrochemical performance. As a result, compared with the planar electrode, the Ti/Pt–NF/PbO2 electrode showed more effective electrochemical decomposition toward nitrilotriacetic acid (80%) and ethylenediaminetetraacetic acid (83%), which are commonly used as chelating agents in nuclear decontamination.

(Invited) Single Cell Voltages for Safety, Predictive Maintenance, and Process Optimization of Industrial Scale Bipolar Electrolyzers (Learned Lessons From Over 30 Years Experience in Chlor-Alkali-Electrolysis)

Just like the membrane electrolysis process in the Chlor-Alkali industry 30 years ago, water electrolysis is facing a major transformation from a niche technology to become a global commodity business. 30 years ago, the unique risks of big bipolar electrolyzers were not recognized by the industry. Lessons learned from incidents and near misses led R2 to the development of the EMOS® Safety System: the state-of-the-art single cell voltage-based safety instrumented system for bipolar electrolyzers. Today, the EMOS® Safety System has become a standard in the Chlor-Alkali industry. With plans announced for much larger electrolyzers and several times higher current densities and their increasing risks, water electrolysis should be spared this painful learning process. Fortunately, EMOS® Safety System supports also bipolar water electrolyzers. Short circuits, separator failures etc. can be only detected with single cell current-voltage-curves to turn the power supply off before explosive gas reaches areas with dangerous high gas holdup.Same time the single cell voltages are used to detect any abnormal cell aging as early as possible and to correlate it with the operating conditions. For this purpose, automatically during the electrolyzer startup a neural network is trained to predict the cell voltages afterwards in real-time and to alarm already a deviation of a few mV from the measured cell voltage. Together with KPI’s like U0 and k, automatically calculated by analyzing load changes from normal electrolyzer operation for each cell, predictive maintenance, cell performance specific replacement and process optimization is possible, customized for the individual industrial plant.Examples from industrial scale electrolyzers concerning safety, maintenance and performance optimization will be presented.

Anodic Catalyst Support via Titanium Dioxide-Graphene Aerogel (TiO2-GA) for A Direct Methanol Fuel Cell: Response Surface Approach

The direct methanol fuel cell (DMFC) has the potential for portable applications. However, it has some drawbacks that make commercialisation difficult owing to its poor kinetic oxidation efficiency and non-economic cost. To enhance the performance of direct methanol fuel cells, various aspects should be explored, and operational parameters must be tuned. This research was carried out using an experimental setup that generated the best results to evaluate the effectiveness of these variables on electrocatalysis performance in a fuel cell system. Titanium dioxide-graphene aerogel (TiO2-GA) has not yet been applied to the electrocatalysis area for fuel cell application. As a consequence, this research is an attempt to boost the effectiveness of direct methanol fuel cell electrocatalysts by incorporating bifunctional PtRu and TiO2-GA. The response surface methodology (RSM) was used to regulate the best combination of operational parameters, which include the temperature of composite TiO2-GA, the ratio of Pt to Ru (Pt:Ru), and the PtRu catalyst composition (wt%) as factors (input) and the current density (output) as a response for the optimisation investigation. The mass activity is determined using cyclic voltammetry (CV). The best-operating conditions were determined by RSM-based performance tests at a composition temperature of 202 °C, a Pt/Ru ratio of (1.1:1), and a catalyst composition of 22%. The best response is expected to be 564.87 mA/mgPtRu. The verification test is performed, and the average current density is found to be 568.15 mA/mgPtRu. It is observed that, after optimisation, the PtRu/TiO2-GA had a 7.1 times higher current density as compared to commercial PtRu. As a result, a titanium dioxide-graphene aerogel has potential as an anode electrocatalyst in direct methanol fuel cells.

Layered Design of a Highly Repeatable Electroactive Biofilm for a Standardized Biochemical Oxygen Demand Sensor.

Microbial electrochemical sensors are promising to monitor bioavailable organics in real environments, but their application is restricted by the unpredictable performance of the electroactive biofilm (EAB), which is randomly acclimated from environmental microflora. With a long-term stable EAB as a template, we successfully designed EAB (DEAB) by the sequential growth of Geobacter anodireducens and automatched microbes, achieving a reproducible high current than those naturally acclimated from wastewater (NEAB). Pre-inoculation of planktonic aerobes as oxygen bioscavengers was necessary to ensure the colonization of Geobacter in the inner layer, and the abundant Geobacter (50%) in DEAB guaranteed 4 times higher current density with a 15-fold smaller variation among 20 replicates than those of NEAB. The sensor constructed with DEAB exhibited a shorter measuring time and a precise biochemical oxygen demand (BOD) measurement with acetate, real domestic wastewater, and supernatant of anaerobic digestion. Here, we for the first time proposed an applicable strategy to standardize EABs for BOD sensors, which is also crucial to ensure a stable performance of all bioelectrochemical technologies.

Bi/UiO-66-derived electrocatalysts for high CO2-to-formate conversion rate

In the CO2 electrocatalytic reduction reaction (CO2RR) technology, high CO2 conversion rate is highly required for efficient CO2 utilization from the CO2 resource. In this study, we propose the strategy of combining UiO-66 metal organic framework (MOF) structure with Bi electrocatalyst for highly active CO2RR with selective formic acid production. The synthesized Bi/UiO-66 catalyst shows superior CO2 reduction property, 4.6 times higher current density at −0.7 V vs. reversible hydrogen electrode (RHE) than bare Bi without UiO-66 despite of low electrochemical surface area. Also, NH2 functionalized UiO-66 shows almost no effect on CO2RR as compared to without NH2 probably due to disassembled linkers during CO2RR. Various characterizations such as Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) indicate carbonate species captured form of CO2 at Zr-MOF site should contribute the high CO2 conversion rate. Our findings demonstrate the feasibility of Zr-MOF as a Supporting material to achieve efficient CO2 reduction.

Co-electrodeposited PtPd anodic catalyst for the direct formic acid fuel cells

This investigation displayed a superb catalytic performance toward the formic acid electro-oxidation reaction (FAOR) in an alkaline medium at a binary catalyst composed of Pt and Pd that were simultaneously electrodeposited onto a glassy carbon (GC) surface. Interestingly, the proposed PtPd/GC catalyst displayed a significant enhancement in the catalytic activity (by ca. 12 times higher direct (Ipd) to indirect (Ipind) current ratio concurrently with ca. -91 mV shift in the onset potential (Eonset) and stability (ca. 2.5 times higher current density after 3600 s of continuous electrolysis) toward FAOR if compared to the Pt/GC catalyst. The catalytic enhancement was thought to arise mostly from minimizing the CO adsorption, i.e., third body effect, at the Pt surface during FAOR.

Ni-Pt coating on graphene based 3D printed electrodes for hydrogen evolution reactions in alkaline media

Additive manufacturing (AM), a three-dimensional (3D) printing method has attracted great attention in manufacturing technology because of the low cost of fabrication of medium to small sizes of products, fast prototyping, and high precision. The 3D printing method has emerged as an innovative interface in electrode applications due to the opportunity to use conductive Polylactic Acid (PLA) filaments. In this study, Nickel (Ni) and Platinum (Pt) with different metal ratios were deposited on 3D printed electrodes and prepared using conductive graphene-based PLA filament. Then, the NiPt coated 3D printed graphene-based electrodes were modified by different metal ratios of Ni/Pt: 1:1, 1:2, and 1:3, called NiPt1, NiPt2, and NiPt3, respectively. The physical properties of the NiPt coated 3D printed electrodes were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), FE-SEM/Energy Dispersive X-ray Spectroscopy (FE-SEM/EDX), FE-SEM mapping, X-ray Powder Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) techniques. Electrochemical measurements of the electrodes were examined by using Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS), Tafel polarization analysis and Chronoamperometry (CA) techniques. The results showed that on NiPt3 3D printed electrode surface, the current density was improved by 25% compared to the other electrode samples. Moreover, it was found that the NiPt3 coated 3D printed electrode had 1.5 times higher current density than the NiPt1 coated 3D printed electrode for HER.

Structural and enhanced photoelectrochemical cell properties of α-hematite -molybdenum disulfide and polyhexylthiophene nanodiamond based nanocomposite prepared by sol-gel method

The α-Fe2O3-MoS2 nanocomposite materials were synthesized using sol-gel technique and investigated by using scanning electron microscopy (SEM), FTIR, X-ray diffraction, UV–vis and Raman analyses. In this study, we used the conducting polymer electrode named polyhexylthiophene (RRPHTh) with nanodiamond (ND) nanomaterials abbreviated as “RRPHTh + ND”. The photocurrent, “electrode” & the “electrolyte” interface of “α-Fe2O3-MoS2″ and ”RRPHTh + ND“ nanocomposite films were studied using the electrochemical method. The developed MoS2-α-Fe2O-RRPHTh + ND nanocomposite films showed ∼ 3 times higher current–density and energy conversion efficiency as compared to the parent “electrode” in an electrolyte of 1 M of NaOH in “photoelectrochemical (PEC) cell”. Furthermore, improved hydrogen release was observed for the Fe2O3-MoS2 and ”RRPHTh + ND“ nanomaterials-based electrodes when compared to aluminum doped Fe2O3, Fe2O3, and MoS2 doped-Fe2O3 films.

Sustainable Neodymium Recovery Using an Electrochemical Approach

Neodymium is a technologically important metal in green energy due to its properties which are critical in wind turbines as permanent magnets and in rechargeable batteries for electric vehicles. However, its production and supply are concentrated in China and this, together with its high demand, has led to categorise it as a critical metal. Therefore, instead of relying exclusively on mining, neodymium recovery from end of life products is one of the most interesting ways to tackle the availability.Our research has been focused on electrolyte synthesis to attain Nd in the metallic and more expensive form via electrodeposition as an environmentally friendly approach.Electrochemical deposition of neodymium has also been attempted in several ionic liquids, but only been partially successful in phosphonium -based ILs, therefore that family of ionic liquids have been at the core of our research. The long alkyl chain trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P66614][TFSI], have been selected due to its hydrophobic properties and electrochemical stability. The effect of concentration and water has been explored in our research concluding that, in fact, water promoted the Nd electrodeposition. A three-fold increase in current densities was observed in comparison with the analogous mixture with less water, which leads to more abundant deposits.[1] , [2] An in-depth study of the Nd3+ solvation in the bulk electrolyte indicated the presence of both bis(trifluoromethylsulfonyl)imide (TFSI) and water in the solvation sphere, as well as insight into the different mode of coordination of TFSI with Nd3+ (i.e. cis/ trans and mono/bidentate).More recently, we have reported a cleaner approach to recover Nd using a pyrrolidinium non-fluorinated ionic liquid (IL) (N-butyl-N-methylpyrrolidinium dicyanamide ([C4mpyr][DCA])) in the presence of neodymium nitrate. The main advantages of these electrolyte mixtures, is the elimination of higher risk of persistence, ecotoxicity when fluorine is decomposed. Additionally, relatively low manufacturing cost as opposed to fluorinated systems as contain only carbon and nitrogen. Our results presented eight times higher current density (-38 mA cm-2) at a lower temperature (halved to 50 °C) and less controlled environment (0.15 – 4.6 wt% H2O) compared to the literature.[3] This is translated into a more cost-effective recovery process. [1] Laura Sánchez-Cupido, Jennifer M. Pringle, Amal L. Siriwardana, Ainhoa Unzurrunzaga, Matthias Hilder, Maria Forsyth, Cristina Pozo-Gonzalo, “Water Facilitated Electrodeposition of Neodymium in a Phosphonium-based Ionic Liquid”, The Journal of Physical Chemistry Letters, 2019, 10, 2, 289-294 [2] Laura Sanchez Cupido, Jennifer M. Pringle, Amal Siriwardana, Matthias Hilder, Maria Forsyth, Cristina Pozo-Gonzalo,” Correlating electrochemical behaviour and speciation in neodymium ionic liquid electrolyte mixtures in the presence of water”, ACS Sustainable Chemistry & Engineering, 2020, 8, 14047-14057 [3] Kalani Periyapperuma, Jennifer M. Pringle, Laura Sanchez-Cupido, Maria Forsyth, and Cristina Pozo-Gonzalo,“Fluorine-Free Ionic Liquid Electrolytes for Sustainable Neodymium Recovery Using an Electrochemical Approach, Green chemistry”, 2021, DOI: 10.1039/D1GC00361E

An Electrocatalytic Activity of AuCeO2/Carbon Catalyst in Fuel Cell Reactions: Oxidation of Borohydride and Reduction of Oxygen

This paper describes the investigation of electrocatalytic activity of the AuCeO2/C catalyst, prepared using the microwave irradiation method, towards the oxidation of sodium borohydride and oxygen reduction reactions in an alkaline medium. It was found that the obtained AuCeO2/C catalyst with Au loading and electrochemically active surface area of Au nanoparticles (AuNPs) equal to 71 µg cm−2 and 0.05 cm2, respectively, showed an enhanced electrocatalytic activity towards investigated reactions, compared with the Au/C catalyst with an Au loading and electrochemically active surface area of AuNPs equal to 78 µg cm−2 and 0.19 cm2, respectively. The AuCeO2/C catalyst demonstrated ca. 4.5 times higher current density values for the oxidation of sodium borohydride compared with those of the bare Au/C catalyst. Moreover, the onset potential of the oxygen reduction reaction (0.96 V) on the AuCeO2/C catalyst was similar to the commercial Pt/C (0.98 V).