Activity For Oxidation Reaction Research Articles

Optimizing Hydrazine Activation on Dual‐Site Co‐Zn Catalysts for Direct Hydrazine‐Hydrogen Peroxide Fuel Cells

ABSTRACTDirect hydrazine‐hydrogen peroxide fuel cells (DHzHPFCs) offer unique advantages for air‐independent applications, but their commercialization is impeded by the lack of high‐performance and low‐cost catalysts. This study reports a novel dual‐site Co‐Zn catalyst designed to enhance the hydrazine oxidation reaction (HzOR) activity. Density functional theory calculations suggested that incorporating Zn into Co catalysts can weaken the binding strength of the crucial N2H3* intermediate, which limits the rate‐determining N2H3* desorption step. The synthesized p‐Co9Zn1 catalyst exhibited a remarkably low reaction potential of −0.15 V versus RHE at 10 mA cm−2, outperforming monometallic Co catalysts. Experimental and computational analyses revealed dual active sites at the Co/ZnO interface, which facilitate N2H3* desorption and subsequent N2H2* formation. A liquid N2H4‐H2O2 fuel cell with p‐Co9Zn1 catalyst achieved a high open circuit voltage of 1.916 V and a maximum power density of 195 mW cm−2, demonstrating the potential application of the dual‐site Co‐Zn catalyst. This rational design strategy of tuning the N2H3* binding energy through bimetallic interactions provides a pathway for developing efficient and economical non‐precious metal electrocatalysts for DHzHPFCs.

Enhanced Adsorption Kinetics and Capacity of a Stable CeF3@Ni3N Heterostructure for Methanol Electro‐Reforming Coupled with Hydrogen Production

Alkaline methanol‐water electrolysis system is regarded as an appealing strategy for electro‐reforming methanol into formate and producing hydrogen with low energy‐consumption compared with alkaline water electrolysis. However, stability and selectivity under high current densities for practical application remain challenging. Herein, a CeF3@Ni3N nanosheets array anchored on carbon cloth (CeF3@Ni3N/CC) was fabricated. The gradual extrusion of F species from Ni(OH)2 lattices can stabilize hierarchical structure and construct abundant heterostructure interfaces. Moreover, CeF3 can modulate electron distribution of Ni3N, thus simultaneously enhancing the surface adsorption kinetics and capability of methanol and OH‐, which is conducive to enhanced methanol oxidation reaction (MOR) activity and selectivity. Therefore, bifunctional CeF3@Ni3N/CC exhibits low potential of 1.43 V at 500 mA cm‐2, along with high stability over 72 h and high faradaic efficiency (FEs) in MOR, as well as an overpotential of 76 mV to achieve 50 mA cm‐2 for hydrogen evolution reaction (HER). Furthermore, membrane‐free CeF3@Ni3N/CC||CeF3@Ni3N/CC cell for MOR||HER delivers high electrocatalytic activity, long‐term stability and FEs at high current density of 300 mA cm‐2. This study highlights the importance of optimizing surface adsorption behavior of active species, as well as rational design of highly efficient heterostructure electrocatalysts for methanol upgrading coupled with hydrogen production.

Enhanced Adsorption Kinetics and Capacity of a Stable CeF3@Ni3N Heterostructure for Methanol Electro-Reforming Coupled with Hydrogen Production.

Alkaline methanol-water electrolysis system is regarded as an appealing strategy for electro-reforming methanol into formate and producing hydrogen with low energy-consumption compared with alkaline water electrolysis. However, stability and selectivity under high current densities for practical application remain challenging. Herein, a CeF3@Ni3N nanosheets array anchored on carbon cloth (CeF3@Ni3N/CC) was fabricated. The gradual extrusion of F species from Ni(OH)2 lattices can stabilize hierarchical structure and construct abundant heterostructure interfaces. Moreover, CeF3 can modulate electron distribution of Ni3N, thus simultaneously enhancing the surface adsorption kinetics and capability of methanol and OH-, which is conducive to enhanced methanol oxidation reaction (MOR) activity and selectivity. Therefore, bifunctional CeF3@Ni3N/CC exhibits low potential of 1.43 V at 500 mA cm-2, along with high stability over 72 h and high faradaic efficiency (FEs) in MOR, as well as an overpotential of 76 mV to achieve 50 mA cm-2 for hydrogen evolution reaction (HER). Furthermore, membrane-free CeF3@Ni3N/CC||CeF3@Ni3N/CC cell for MOR||HER delivers high electrocatalytic activity, long-term stability and FEs at high current density of 300 mA cm-2. This study highlights the importance of optimizing surface adsorption behavior of active species, as well as rational design of highly efficient heterostructure electrocatalysts for methanol upgrading coupled with hydrogen production.

The Effect of Saccharin on SnNi Alloy: the Electrodeposition and its Electrocatalytic Activity in Ethanol Oxidation Reaction

The development of Direct Ethanol Fuel Cell (DEFC) has attracted much attention, as alternative energy sources due to its various advantages. However, among its various advantages, DEFC has several problems, such as the kinetics of the ethanol oxidation reaction. Transition metal-based catalysts such as nickel and tin are considered as potential catalysts for DEFC due to their oxophilic properties that can improve catalytic activity. In this study, the effect of saccharin on SnNi bimetallic alloy catalyst synthesized by electrodeposition method on copper wire substrate was investigated. SnNi samples were characterized by several techniques, including X-ray diffraction, Scanning electron microscopy, and energi dispersive X-ray spectrocopy. Saccharin addition had a significant effect on the morphology, crystallite size, and composition of the catalyst. The presence of saccharin causes the formation of more uniform particles and has a smaller size. The sample with the addition of saccharin had a smaller charge transfer resistance value 4.82 Ω, lower tafel slope by 115 mV/dec, and show higher jf/jb ratio by 0.55. Furthermore, as the current density decreases, the SnNi catalyst with saccharin has a slow decrease rate and higher stability than the SnNi catalyst without saccharin.

Novel Gel method MXene-Supported Dual-Site PtNi-NiO for Electrocatalytic Water Reduction and Urea Oxidation.

Compared to the traditional oxygen evolution reaction (OER), the urea oxidation reaction (UOR) generally exhibits a lower overpotential during the electrolytic process, which is conducive to the hydrogen evolution reaction (HER) at the cathode. The superior structure and abundant sites play a crucial role in promoting the adsorption and cleavage of urea molecules. Therefore, this paper introduces a simple metal cation-induced gelation method to prepare an electrocatalyst with PtNi alloy-NiO dual sites supported on Ti3C2Tx, which simultaneously exhibits excellent UOR and HER performance. PtNi-NiOx/Ti3C2Tx demonstrates good catalytic activity for the urea oxidation reaction, requiring only 1.364V (overpotential of 0.994V) to achieve a current density of 100mAcm-2 in UOR, and also exhibits remarkable catalytic activity in the hydrogen evolution reaction, with PtNi-NiOx/Ti3C2Tx achieving a current density of 10mAcm-2 in HER with only 24mV of overpotential. In the UOR//HER two-electrode electrolysis cell, it requires only 1.361 and 1.538V to reach current densities of 10 and 100mAcm-2, respectively. According to density functional theory (DFT) calculations, the dual active sites can intelligently adsorb the electron-donating/electron-withdrawing groups in urea molecules, activate chemical bonds, and thereby initiate urea decomposition.

Aerobic Thiols Oxidative Coupling to Disulfides over Robust CoOx Nanoclusters Confined within Hierarchical Silicalite-1 Zeolite.

Disulfide is an important organic reagent and synthetic intermediate that is widely used in organic synthesis, polymers, and other fields, but its synthesis still suffers from many environmental pollution and economic problems. Here, we present an environmentally friendly and efficient base-free aerobic oxidative thiol coupling catalyzed by heterogeneous CoOx nanoclusters entrapped in hierarchical silicalite-1 zeolite, synthesized by combining silane pore expansion and metal coordination methods under hydrothermal conditions. It is confirmed that open hierarchical channels favor mass diffusion, and the chemical valence of Co species in CoOx/h-S-1-H is +2, which is different from that of Co3O4 particles in CoOx/h-S-1-I. CoOx nanoclusters, are strongly fixed in the channels of silicalite-1 zeolite via Co-O-Si bonds, which is of great importance for the high catalytic activity in both symmetrical and unsymmetrical oxidative thiol coupling reactions. After recycling experiments four times, the CoOx/h-S-1-H used has almost the same chemical state and the same distribution of Co(II) species as the fresh catalysts. Based on DFT calculations and inhibition experiments, the oxidative coupling of thiols undergoes a free radical mechanism in which Co(III) causes RS-H cleavage into RS· and H· species. Subsequently, two RS· radicals are coupled to disulfides, while H· radicals react with the O species to form H2O molecules. This work not only provides guidance on catalyst design and parameter optimization for oxidative thiol coupling but also advances the understanding of the aerobic oxidation mechanism.

Immobilization of Metal Nanoparticles to an Ultrathin Two-Dimensional Conjugated Metal-Organic Framework for Synergistic Electrocatalysis.

Metal-organic frameworks (MOFs) have been considered as promising hosts for immobilizing ultrafine metal nanoparticles (MNPs) due to their high surface area and porosity. However, electrochemical applications of such emerging composites are severely limited by the poor electrical conductivity and large size of the MOFs. Herein, we report the general synthesis of incorporating various MNPs into a conjugated MOF ultrathin nanosheet (Cu-TCPP UNS) matrix, which not only prevents agglomeration and restricts the growth of MNPs but also benefits the exposure of active sites and the transport of electrons. Specifically, the obtained PtCu@Cu-TCPP UNSs exhibited nearly two times higher mass activity for the methanol oxidation reaction (MOR) than the commercial Pt/C catalyst. Mechanistic studies reveal that the strong interaction between MNPs and Cu-TCPP promotes the oxidation of the CO intermediate. Moreover, the PtCu@Cu-TCPP UNSs can be employed as bifunctional electrocatalysts to couple MOR with the hydrogen evolution reaction for highly efficient hydrogen production.

Bifunctional system constructed by NiCu-F/DSA electrode self-coupling for efficient removal of ammonia nitrogen from landfill leachate

ABSTRACT Landfill leachates containing high concentrations of ammonia nitrogen, due to its strong toxicity, large discharge and great environmental hazard, is in urgent need of efficient cleaning treatment. In this work, Ni1Cu0.25-F/DSA catalytic electrode was prepared via electrodeposition by means of fluorination-induced surface reconstruction. The surface of electrode was determined to be a porous sponge-like structure by physical characterizations. The electrode exhibited a superior ammonia oxidation reaction (AOR) activity and stability by a series of electrochemical tests. On this basis, a Ni1Cu0.25-F/DSA || Ni1Cu0.25-F/DSA bifunctional system was developed for efficient removal of ammonia nitrogen in landfill leachate. The results of denitrification experiment indicated that the removal efficiency of NH4 +-N and TN were 99.89% and 68.9%, respectively, when the electrolytic cell potential was 1.7 V, pH was 13 and the initial ammonia concentration was 600 mg L−1. The NH4 +-N removal efficiency remained above 95% after the cyclic denitrification experiment lasting for 6 days, which validates the robust stability of the electrode.

Empowering Tri-Functional Palladium's Catalytic Activity and Durability in Electrocatalytic Formic Acid Oxidation Reaction via Innovative Self-Caging and Alloying Strategies.

Direct formic acid fuel cells (DFAFCs) stand out for portable electronic devices owing to their ease of handling, abundant fuel availability, and high theoretical open circuit potential. However, the practical application of DFAFCs is hindered by the unsatisfactory performance of electrocatalysts for the sluggish anodic formic acid oxidation reaction (FAOR). Palladium (Pd) based nanomaterials have shown promise for FAOR due to their highly selective reaction mechanism, but maintaining high electrocatalytic durability remains challenging. In this study, a novel Pd-based electrocatalyst (UiO-Pd-E) is reported with exceptional durability and activity for FAOR, which can be attributed to the Pd nanoparticles encapsulated within a carbon framework where concurrent chemical alloying of Pd and Zr occurs. Further, the UiO-Pd-E demonstrates noteworthy multifunctionality in various electrochemical reactions including electrocatalytic ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) in addition to the FAOR, highlighting its practical potentials.

Balanced adsorption and oxidation in a porous P, N-doped carbon prepared by melt-salt-mediated strategy for enhanced fenton-like reaction

The activation of persulfate oxidation processes using carbon-based catalysts is attractive for eliminating persistent aromatic organic pollutants in wastewater treatment. Herein, N and P co-doped carbonaceous (NPC) catalysts with an ultrahigh surface area were synthesized using a melt-salt-mediated strategy, employing Zeolitic Imidazolate Framework-8 as a self-sacrificing template. The NPC(1:1) carbon, prepared under optimized conditions, exhibited the highest surface area of 2001.5 m2/g, characterized by the highest number of defects and a high dispersion of N (1.89 %) and P (0.30 %) atoms on the carbon. This carbon catalyst exhibited a high capacity for adsorption and potential for activating persulfates in the removal of p-Nitrophenol (p-NP). Experimental data indicate a balance between adsorption and oxidation in the NPC(1:1)/PDS/p-NP system, with the highest catalytic removal rate achieved through moderate pre-adsorption of p-NP. Evidence from quenching, electron paramagnetic resonance (EPR), and amperometric i-t experiments suggests that the NPC(1:1)/PDS system primarily degrades p-NP through an electron transfer pathway. Defects in carbon and graphitic N were identified as catalytic sites. These defects resulted in an electron-deficient state, which leads to the activation of PDS and graphitic N was more reactive than both pyridinic and pyrrolic N in the adsorption of PDS molecules. Additionally, P-containing groups such as C-P-O, C-O-P, and C3-P were pinpointed as active sites on the carbons through DFT calculations. The intermediates during p-NP degradation were identified, and possible degradation pathways were proposed. A toxicity analysis indicated a significant reduction in overall toxicity following the oxidation treatment. This study provides innovative insights into the balance between adsorption and catalytic activity in porous carbon-activated persulfate oxidation reactions, thereby aiding in the development of enhanced oxidation catalysts for environmental remediation.

Revealing the mechanism of bifunctional PtLa electrocatalyst for highly efficient methanol oxidation, hydrogen evolution, and coupling reaction

The development of clean energy solutions, such as fuel cells and hydrogen energy, is crucial for addressing the global energy shortage. Platinum (Pt)-based catalysts are widely used in fuel cells and hydrogen energy generation (for example, via water electrolysis). However, reducing the amount of Pt used while maintaining the catalytic performance of such catalysts is essential. Herein, PtLa catalysts (PtxLay/C) doped with rare earth element lanthanum (La) with different Pt/La atomic ratios were synthesized using a simple chemical reduction method, resulting in Pt65La35/C, Pt78La22/C, Pt97La3/C, and Pt100/C. These PtxLay/C catalysts exhibited excellent electrocatalytic activity and stability in methanol oxidation reaction (MOR), hydrogen evolution reaction (HER), and their coupling reaction as MOR||HER under alkaline conditions. The mechanism by which La doping enhances the electrocatalytic properties and stability of Pt-based catalysts was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), aberration-corrected scanning transmission electron microscopy (AC-STEM), in-situ Fourier transform infrared (FTIR) and operando Raman spectroscopy. For HER, La doping facilitated the adsorption and activation of H2O at Pt sites, improving water dissociation and *OH desorption and reducing Pt poisoning by *OH. This enhances both the catalytic performance and stability of PtxLay/C for HER. Pt78La22/C exhibited a considerably lower overpotential of only 111 mV at 100 mA cm−2 compared to commercial 20 wt% Pt/C (Pt/C-Johnson Matthey (JM)), which requires 153 mV. For MOR, La promotes CO bond cleavage and reduces CO adsorption at the Pt sites, thereby enhancing both the performance and stability of the catalysts. The mass activity (MA) of Pt78La22/C for MOR is 4.44 A mg−1Pt, which is 12.33 times higher than that of Pt/C-JM (0.36 A/mgPt), and surpasses those of Pt65La35/C, Pt97La3/C, and Pt100/C (2.93, 0.24, and 2.91 A mg−1Pt, respectively). Additionally, Pt78La22/C exhibited outstanding catalytic performance for MOR||HER, with a current density of 20 mA cm−2 at 1.030 V, demonstrating good stability with negligible voltage changes after a 15 h chronoamperometry (CA) testing. This study provides a new strategy for synthesizing Pt-based catalysts with enhanced efficiency and low-energy input for HER||MOR.

Investigation into geometric configurations and electronic properties of CeO2-supported gold clusters

A detailed understanding of the geometric structure and electronic properties of gold nanoparticles on the ceria surface is crucial for comprehending their unique catalytic activity. Using the first-principles method based on density functional theory, the adsorption of Aux (x = 1–4) clusters on the CeO2(111) surface was studied. It was discovered that the standing configurations of Au2 and Au3, as well as the tetrahedral structure of Au4, are the most stable adsorption structures. The stability of these configurations is jointly determined by the number and strength of Au-Au bonds, the Au-O bonding energy, and the interaction dynamics between the clusters and the substrate. The analysis of Bader charge, difference charge density and density of states suggested that lattice relaxation and electronic localization occur in the reduced Ce3+. The reduced amount and location of Ce3+ are significantly influenced by the position and charge transfer amount of Aux cluster. The adsorption of CO on Au4/CeO2(111) indicated that stronger Au-C bonding energy due to the hybridization of Au-5d and C-2p, thereby enhancing the catalytic activity for CO oxidation reactions.

Membrane‐Free Electrocatalytic Co‐Conversions of PBS Waste Plastics and Maleic Acid into High‐Purity Succinic Acid Solid

AbstractPlastic pollution, an increasingly serious global problem, can be addressed through the full lifecycle management of plastics, including plastics recycling as one of the most promising approaches. System design, catalyst development, and product separation are the keys in improving the economics of electrocatalytic plastics recycling. Here, a membrane‐free co‐production system was devised to produce succinic acid (SA) at both anode and cathode respectively by the co‐electrolysis of polybutylene succinate (PBS) waste plastics and biomass‐derived maleic acid (MA) for the first time. To this end, Cr3+‐Ni(OH)2 electrocatalyst featuring much enhanced 1,4‐butanediol (BDO) oxidation reaction (BOR) activity has been synthesized and the role of doped Cr has been revealed as an “electron puller” to accelerate the rate‐determining step (RDS) in the Ni2+/Ni3+ cycling. Impressively, an extra‐high SA production rate of 3.02 g h−1 and ultra‐high apparent Faraday efficiency towards SA (FEapparent=181.5 %) have been obtained. A carbon dioxide‐assisted sequential precipitation approach has been developed to produce high‐purity SA and byproduct NaHCO3 solids. Preliminary techno‐economic analysis demonstrates that the reported system is economically profitable and promising for future industrial applications.

Membrane-Free Electrocatalytic Co-Conversions of PBS Waste Plastics and Maleic Acid into High-PuritySuccinic Acid Solid.

Plastic pollution, an increasingly serious global problem, can be addressed through the full lifecycle management of plastics, including plastics recycling as one of the most promising approaches. System design, catalyst development, and product separation are the keys in improving the economics of electrocatalytic plastics recycling. Here, a membrane-free co-production system was devised to produce succinic acid (SA) at both anode and cathode respectively by the co-electrolysis of polybutylene succinate (PBS) waste plastics and biomass-derived maleic acid (MA) for the first time. To this end, Cr3+-Ni(OH)2 electrocatalyst featuring much enhanced 1,4-butanediol (BDO) oxidation reaction (BOR) activity has been synthesized and the role of doped Cr has been revealed as an "electron puller" to accelerate the rate-determining step (RDS) in the Ni2+/Ni3+ cycling. Impressively, an extra-high SA production rate of 3.02 g h-1 and ultra-high apparent Faraday efficiency towards SA (FEapparent=181.5%) have been obtained. A carbon dioxide-assisted sequential precipitation approach has been developed to produce high-purity SA and byproduct NaHCO3 solids. Preliminary techno-economic analysis demonstrates that the reported system is economically profitable and promising for future industrial applications.

Controlled formation of CoOOH/Co(III)-MOF active phase for boosting electrocatalytic alkaline water oxidation

Surface reconstituted metal-organic frameworks (MOFs) offer appealing properties for electrocatalysis due to their unique structural and compositional advantages. In this work, a controlled potential-induced reconstruction of a two-dimensional cobalt metal-organic framework for boosting oxygen evolution reaction in alkaline media is reported. The current MOF is shown to undergo a partial structural transformation that generates a heterogeneous system, where the original MOF coexists with an oxyhydroxide phase. In fact, the potential-induced stabilization of Co(III) metal centers in the MOF is crucial for delaying its full degradation in alkaline media. This partial retention of the Co(III)MOF phase in the so-derived heterogeneous catalyst has been demonstrated to be decisive for boosting the alkaline electrocatalytic oxygen evolution reaction (OER), displaying superior OER activity in terms of both thermodynamic and kinetic merits compared to the benchmark IrO2 and RuO2 electrocatalysts and the prototypical cobalt (oxy)hydroxides, with a Tafel slope of 52 mV dec−1 and a turnover frequency (TOF) of 6.8 s−1 at 450 mV. Remarkably, the generated final product is stable, exhibiting high robustness and long durability for long-term OER electrolysis. This work provides new insight into the impact of the reconstruction of a MOF for alkaline OER under typical electrochemical conditions, which ultimately benefits the rational design of MOF-based catalysts with high electrocatalytic activity for oxidation reactions.

Plasma-Constructed Co2P-Ni2P Heterointerface for Electro‑Upcycling of Polyethylene Terephthalate Plastic to Co-Produce Hydrogen and Formate.

Integrating electrochemical upcycling of polyethylene-terephthalate (PET) and the hydrogen evolution reaction (HER) is an energy-saving approach for electrolytic hydrogen (H2) production, along with the coproduction of formate. Herein, a novel and rapid strategy of cold plasma phosphating is employed to synthesize Co2P-Ni2P heterointerface decorated on carbon cloth (Co2P-Ni2P/CC) to catalyze H2 generation and reform PET. Notably, the obtained Co2P-Ni2P/CC exhibits eminent ethylene glycol oxidation reaction (EGOR) and HER activities, effectuating low potentials of merely 1.300 and -0.112V versus RHE at 100mAcm-2 for the EGOR and HER, respectively, also attaining an ultralow cell bias of 1.300V at 10mAcm-2 for EG oxidation assisted-water splitting. DFT and characterization results validate that the as-formed built-in electric fields in the Co2P-Ni2P heterointerface can accelerate electrons transfer and deepen structural self-reconstruction, thereby boosting effectively water dissociation and ethylene glycol (EG) dehydrogenation. Impressively, coupling HER with PET-derived EG-to-formate in a flow-cell electrolyzer assembled with Co2P-Ni2P/CC pair achieves an intriguing formate Faradaic efficiency of 90.6% and an extraordinary stable operation of over 70h at 100mAcm-2. The work exemplifies a facile and effective strategy for synthesizing metal phosphides electrocatalysts with extraordinary performance toward H2 generation of water splitting and recycling of PET.

Electrochemical Synthesis of a Composite of Few-Layer Graphene Structures with PdNi-Alloy Nanoparticles and Its Electrocatalytic Activity in the Methanol Oxidation Reaction

Electrochemical Synthesis of a Composite of Few-Layer Graphene Structures with PdNi-Alloy Nanoparticles and Its Electrocatalytic Activity in the Methanol Oxidation Reaction

Dual-doped medium-entropy phosphides for complete urea electrolysis

Developing dual-functional electrocatalysts for urea-water decomposition still faces significant challenges. In this study, the vanadium (V) and cerium (Ce) co-doped FeCoNi medium-entropy phosphide (VCe-FeCoNiP/NF) were effectively fabricated on nickel foam (NF) via “two-step method,” which involved hydrothermal treatment followed by phosphorization. Experimental results indicate that, benefiting from dual-ion doping and medium-entropy configuration, VCe-FeCoNiP/NF demonstrates unique electronic effects among the multimetallic elements, thereby exhibited remarkable catalytic activity for both urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Under urea-water conditions (1 M KOH with 0.33 M urea), the VCe-FeCoNi/NF catalyst merely required 1.338 V (vs RHE) and an overpotential of 173 mV to attain a current density of 100 mA·cm−2 for UOR and HER, respectively. Moreover, it could stably operate at a current density of 20 mA·cm−2 for 225 h in overall urea-water decomposition. This work provides new insights for designing high-performance urea-water electrolysis catalysts.

Electrocatalysis of hydrogen and oxygen electrode reactions in alkaline media by Rh-modified polycrystalline Ni electrode

Developing novel electrocatalysts for energy conversion applications is of utmost importance for reaching the energy security of modern society. Here we present a comprehensive investigation of rhodium-modified polycrystalline nickel as an electrocatalyst for hydrogen and oxygen electrode reactions in alkaline media. The surface modification of nickel electrodes was achieved by facile galvanic displacement (up to 30 s) from a highly concentrated acidic Rh3+ solution. The results demonstrate a significant enhancement in the electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on the Rh-modified Ni electrodes, positioning galvanic displacement as a viable approach to engineering advanced electrocatalysts for clean energy applications. On the other hand, the hydrogen oxidation (HOR) and oxygen reduction reaction (ORR) activities of the Rh-modified electrodes are lower compared to polycrystalline platinum. It is suggested that semiconducting Rh2O3 has a detrimental role on the HOR and ORR performance, while the activities of HER and OER, dominantly taking place on metallic Rh and conductive RhO2, are very high. This research sheds light on the mechanisms underlying the enhanced electrode kinetics on Rh-modified Ni electrodes and provides insights into the development of efficient and cost-effective electrocatalysts for renewable energy technologies.

Physical insight into the enhanced urea electrooxidation using Ni and Fe-based LDH, LDO, and hydroxides under different dissolved gas saturation conditions in electrolyte

The production of green hydrogen is one of the most demanding and challenging for modern technology. A promising and an effective approach is electrocatalytic anodic urea oxidation reaction to generate hydrogen at cathode under alkaline electrolysis condition. However, it remains crucial for the development of active and stable electrocatalysts for efficient urea oxidation. In this study, we employed the hydrothermal synthesis route for NiFe LDH, NiFe LDO, and Ni(OH)2. The superior performance of NiFe LDH compared to other catalysts is observed due to easy charge transfer facilitated by Fe ions. Moreover, Fe incorporation prevents surface poisoning of the electrocatalyst, resulting in increased activity and stability for electrocatalytic urea oxidation reaction. The influence of different electrolyte environments on the performance of urea-based electrolyzers for sustainable hydrogen production and management of urea-rich wastewater has been measured for the first time by varying oxygen saturation and nitrogen purging conditions. In cyclic voltammetry studies, O2-saturated and purging conditions outperformed N2 gas saturation or purging. The findings of this study provide valuable insight into the design of practical and environmentally friendly urea electrooxidation systems.