Onset Potential Research Articles

Unveiling the Pivotal Role of dx2-y2Electronic States in Nickel-based Hydroxide Electrocatalysts forMethanol Oxidation.

The anodic methanol oxidation reaction (MOR) plays a crucial role in coupling with the cathodic hydrogen evolution reaction (HER) and enables the sustainable production of the high-valued formate. Nickel-based hydroxide (Ni(OH)2) as MOR electrocatalyst has attracted enormous attention. However, the key factor determining the intrinsic catalytic activity remains unknown, which significantly hinders the further development of Ni(OH)2 electrocatalyst. Here, we found that the dx2-y2electronic state within antibonding bands plays a decisive role in the whole MOR process. The onset potential depends on the deprotonation ability (Ni2+ to Ni3+), which was closely related to the band center of dx2-y2orbital. The closer ofdx2-y2 orbital to the Fermi level showed the stronger the deprotonation ability. Meanwhile, in the high potential region, the broadening of dx2-y2orbital would facilitate the electron transfer from methanol to catalysts (Ni3+ to Ni2+), further enhancing the catalytic properties. Our work for the first time clarifies the intrinsic relationship between dx2-y2electronic state and the MOR activities, which adds a new layer of understanding to the methanol electrooxidation research scene.

Unveiling the Pivotal Role of dx2‐y2 Electronic States in Nickel‐based Hydroxide Electrocatalysts for Methanol Oxidation

The anodic methanol oxidation reaction (MOR) plays a crucial role in coupling with the cathodic hydrogen evolution reaction (HER) and enables the sustainable production of the high‐valued formate. Nickel‐based hydroxide (Ni(OH)2) as MOR electrocatalyst has attracted enormous attention. However, the key factor determining the intrinsic catalytic activity remains unknown, which significantly hinders the further development of Ni(OH)2 electrocatalyst. Here, we found that the dx2‐y2 electronic state within antibonding bands plays a decisive role in the whole MOR process. The onset potential depends on the deprotonation ability (Ni2+ to Ni3+), which was closely related to the band center of dx2‐y2 orbital. The closer of dx2‐y2 orbital to the Fermi level showed the stronger the deprotonation ability. Meanwhile, in the high potential region, the broadening of dx2‐y2 orbital would facilitate the electron transfer from methanol to catalysts (Ni3+ to Ni2+), further enhancing the catalytic properties. Our work for the first time clarifies the intrinsic relationship between dx2‐y2 electronic state and the MOR activities, which adds a new layer of understanding to the methanol electrooxidation research scene.

Ligand-modified nanoparticle surfaces influence CO electroreduction selectivity

Improving the kinetics and selectivity of CO2/CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp2 hybridization of CO(ad), facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC–CH2)* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C–O, Cu–C, and C–S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.

NdMn1.5Ru0.5O5, a high-performance electrocatalyst with low Ru content for acidic oxygen evolution reaction

A mixed oxide with the crystal structure of the DyMn2O5 family, namely NdMn1.5Ru0.5O5, is reported active for the oxygen evolution reaction (OER) in acidic media. NdMn1.5Ru0.5O5 displays high OER activity of 500 A gRu−1 at 1.5 V. Moreover, is more stable than most Ru oxides reported to date, remaining active for more than 500 cycles between 1.1. and 1.7 V at low scan rate of 10 mV s−1. The high activity and stability are attributed to the Ru cations, as NdMn2O5 exhibits very low OER activity. NdMn1.5Ru0.5O5 has particularly short Ru–Ru distances of 2.60 Å, a value close to the Ru–Ru metallic distances around 2.642 Å. The high activity and durability of NdMn1.5Ru0.5O5 for the OER are also demonstrated in a proton exchange membrane water electrolysis cell by producing a low-loaded anode electrode with 0.5 mgRucm−2. The cell achieves 1.97 V at 0.5 A cm−2, consistent with the performances reported for Ru-based catalysts but with lower Ru loading. This performance is maintained during 100 h of operation. Additionally, NdMn1.5Ru0.5O5 displays visible ORR activity in acidic media, recording an onset potential of 0.85 V at 0.1 mA cm−2. It is noteworthy to highlight the extreme rarity of bifunctional ORR/OER catalysts acidic media.

Insight into the d–p Orbital Hybridization of Ru and B Dispersed g‐C3N4 Catalysts for Nitrogen Reduction Reaction

AbstractElectrochemical nitrogen reduction reaction (NRR) is considered as an important strategy for ammonia using green energy. Single atom catalysts (SACs) with a metal atom as active site have been shown its advantages to high ammonia yield and low energy consumption. In this work, we proposed a new concept of SACs with the capacity of d‐p orbital hybridization. These computationally designed SACs contained a metal and non‐metal pair anchored on g‐C3N4 slab. Among these SACs studied in the present work, RuB@g‐C3N4 catalyst performed the best activity for NRR with low onset potential of −0.33 V by a two‐step scanning computations using density functional theory (DFT). Moreover, suppressing effectively to the competitive hydrogen evolution reaction (HER) also make it more selective. It was further revealed that the hybridization of d‐p orbitals between metal and nonmetal could regulate the electronics of active sites and facilitate the adsorption and charge transfer of adsorbed N2 molecules resulting in enhanced catalytic performance. This work demonstrated an alternative way to further enhance the catalytic activity of SACs by introducing a non‐metal atom.

Modulating CO2 Electrocatalytic Conversion to the Organics Pathway by the Catalytic Site Dimension.

Electrochemical reduction of carbon dioxide to organic chemicals provides a value-added route for mitigating greenhouse gas emissions. We report a family of carbon-supported Sn electrocatalysts with the tin size varying from single atom, ultrasmall clusters to nanocrystallites. High single-product Faradaic efficiency (FE) and low onset potential of CO2 conversion to acetate (FE = 90% @ -0.6 V), ethanol (FE = 92% @ -0.4 V), and formate (FE = 91% @ -0.6 V) were achieved over the catalysts of different active site dimensions. The CO2 conversion mechanism behind these highly selective, size-modulated p-block element catalysts was elucidated by structural characterization and computational modeling, together with kinetic isotope effect investigation.

Dimetallic praseodymium-cobalt carbon nanotubes as highly efficient electrocatalyst for oxygen reduction reaction

In this study, six bimetallic rare earth (RE = La, Ce, Pr, Nd, Sm, Eu) cobalt nitrogen doped carbon nanotubes (RECo-NCNTs) were synthesized with g-C3N4 derivative method. These RECo-NCNTs were characterized by SEM, BET, XPS, XRD and Raman. In addition, their catalytic performances for oxygen reduction reaction (ORR) had also been tested. The introduction of rare earths did not destroy the structure of nanotubes but apparently change their ORR performances. The PrCo-NCNTs showed the significant improvement in catalytic ability for ORR (onset potential of 0.95 V and half-wave potential of 0.79 V), which is very close to that of commercial 20 % Pt/C. Moreover, PrCo-NCNTs exhibits an excellent catalytic stability (no activity decay after 10000st cycles) and an outstanding methanol toxic tolerance. Assembled in metal–air batteries (Zn-air, Al-air and Mg-air), the PrCo-NCNTs electrode also presents high power densities and discharge voltages.

The electrocatalytic activity of pomelo peel-derived nitrogen-doped carbon material for oxygen reduction reaction

Exploring the non-precious metal catalysts of oxygen reduction reaction (ORR) becomes the key to promote the industrialization of new energy devices such as fuel cells and metal-air batteries because of the sluggish kinetics of ORR. Three-dimensional N-doped carbon (NC-900) material was obtained using the high-temperature pyrolysis of pomelo peel waste. The prepared NC-900 catalyst possesses an ultra-high specific surface area of 1631.3 m2·g−1, high content of 57.7 ± 0.9% pyrrolic-N, and three-dimensional porous structure. As the ORR catalyst, NC-900 has a onset potential of 0.992 V and half-wave potential of 0.859 V, comparable to 0.988 and 0.872 V of Pt/C. The typical 4-electron pathway of ORR process is occupied by the surface of NC-900. The ORR catalytic activity of NC-900 was almost unaffected by methanol. After 8 h of continuous operation, the reduction current on the surface of NC-900 was decreased only 2.7% of the initial current. Based on these outstanding ORR performances, the pomelo peel-derived NC-900 can serve as a strong competitor for the substitute of Pt/C to promote the potential industrialization of new energy devices.

Novel hydrothermally synthesized NiS nanomaterial decorated over g-CN nanosheet for OER activity

The main objective of the present work is the fabrication of extremely efficient and new electrocatalysts for the water splitting process, which is important for producing clean energy. Cost-effective metal sulfides have demonstrated greater advantages over other materials for OER in an alkaline electrolyte. Despite extensive efforts, we have synthesized the innovative g-CN/NiSnanocomposite using a hydrothermal techniquefor electrocatalytic water splitting. We conducted a comprehensive set of tests toanalyze the electrocatalytic potential ofsynthesizedelectrocatalyst. Furthermore, the kinetic mechanisms of the produced electrocatalyst applied on nickel foam (NF)were investigated by linear sweep voltammetry (LSV). The chronoamperometry, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to determine the stability and catalytic process using a basic (1.0 M KOH) solution. The electrochemical tests of g-CN/NiS nanocomposite exhibit an impressive overpotential 194 mV to achieve ideal current density (Cd) 10 mA cm−2 and have a lowest Tafel value (33 mV dec-1). In addition, compared to a reversible hydrogen electrode (RHE), the nanocomposite exhibits a decrease in onset potential by 1.42 V and has remarkable stability for a duration of 50 h. Hence, it is feasible to enhance electrochemical efficiency byaltering the shape and surface interactions. These features collectively indicate that the electrocatalyst is highly suitable for the OER process.

Magnetic field-enhanced oxygen reduction reaction for electrochemical hydrogen peroxide production with different cerium oxide nanostructures

We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). A continuous magnetic field (2000 Oe) was used for the first time in the literature. The best results were for 5 % (w/w) CeO2 for all three different morphologies, more than doubling the ring current, enhancing the hydrogen peroxide selectivity from 51 % (Vulcan XC-72) to 84–89 %, and modifying the onset potential to lesser negative values. The presence of the magnetic field led to even higher ring currents with 5 % (w/w) CeO2, H2O2 selectivity from 54 % (Vulcan XC-72) to 88–96 % and changing even more the onset potential. Those results were correlated with the Zeeman effect, the Lorentz force, generating magnetohydrodynamic effects, the Kelvin force, and the formation of Bound Magnetic Polarons. This pioneering research introduces an innovative approach, highlighting the potential of an external continuous magnetic field.

Development of a fast and simple electrochemical sensor for trace determination of sulfite using copper(II) triazole complexes

A glassy carbon electrode (GCE) was modified with copper triazole complexes (Cu(L)2) containing three different substituents (OMe, Br, and NO2), and the fabricated electrochemical sensors were used to detect sulfite. The materials were characterized by cyclic voltammetry and scanning electron microscopy (SEM/EDX). The copper(II) 5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carboxylate (Cu(LNO2)2) complex exhibited the best electrochemical performance toward the sulfite electron transfer process regarding onset potential and peak current. Best results were obtained at pH 4, and the following analytical parameters for sulfite detection were determined by amperometry at 0.90 V, as follows: reproducibility (1.9 %), repeatability (1.6 %), limit of detection (0.75 µmol/L), limit of quantification (2.27 µmol/L), dynamic concentration range (10 µmol/L to 5.00 mmol/L, R2 = 0.995), and sensitivity (7.43x10-3 µA µmol−1 L). Precision was evaluated in terms of repeatability, and a relative standard deviation < 15 % was found at three concentration levels. The method́s accuracy was assessed by determining sulfite in commercial wine samples, and acceptable errors were obtained compared to values reported by an external analytical laboratory. The selectivity towards interfering species (Ca2+, Zn2+, Mg2+, NO3−, glucose, sucrose, NaCl, and KCl) and the stability was also evaluated. The practical application of the Cu(LNO2)2/GCE sensor was examined by analyzing the sulfite content in white and red commercial wines.

Fe2W18Fe4@MOF-Ni-100 nanocomposite: Insights into synthesis and application as a promising material towards the electrocatalytic water oxidation

In this research, a new nanocomposite was synthesized via the sol–gel method by encapsulation of tetranuclear sandwich-type hetropolyanion (Na9K[(FeW9O34)2Fe4(H2O)2].32H2O, abbreviated as Fe2W18Fe4, on the surface of MOF-Ni-100 for the first time. The as-prepared nanocomposite (Fe2W18Fe4@MOF-Ni-100) was examined using different microscopy and spectroscopy techniques, including FT-IR, UV–vis, XRD, SEM, EDX, and BET techniques. The assembled Fe2W18Fe4@MOF-Ni-100 nanocomposite served as a potential heterogeneous catalyst in the water oxidation process for the purpose of oxygen evolution reaction (OER) at neutral pH conditions (N2-saturated 0.1 M Na2SO4). The electrochemical characteristics of the Fe2W18Fe4@MOF-Ni-100 nanocomposite was assessed through cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) methods. The desired nanocatalyst displayed a low onset potential of 1.1 V vs. NHE and low overpotential of 269 mV at a current density (j) of 10 mAĊcm−2 with a Tafel slope of 73 mV.dec−1 (pH = 7). Furthermore, the Fe2W18Fe4@MOF-Ni-100 nanocomposite exhibited remarkable stability and retained its catalytic activity even after 200 catalytic cycles.

Efficient hierarchical ZIF-based electro/photocatalyst toward hydrogen generation and evolution

In this study, a well-designed hierarchical BiFeO3/ZIF-67 (BFO-ZIF) composite was successfully synthesized to improve the performance of photocatalytic hydrogen generation in comparison to bare BiFeO3 and ZIF-67. Moreover, the behavior of the resultant electrocatalysts was also investigated in the hydrogen evolution reaction (HER). The synthesized electro-photocatalysts were characterized by various physical and photo/electrochemical analyses. The remarkable outcomes of the composite with 50 wt% of ZIF-67 in hydrogen generation correspond to the high specific surface area of the photocatalyst concurrently with the formation of active sites and new charge channels, leading to a modified charge transfer pathway and lower electron-hole recombination. The maximum H2 generation rate over the optimal BFO-ZIF composite (BFO-ZIF(50)) attained 1617 μmol g−1 h−1 during visible light exposure, surpassing the rates observed for pure BFO and ZIF-67. Furthermore, the BFO-ZIF(50) electrocatalyst, with the onset potential of −0.089 V, resulted in an overpotential of −0.19 V at a current density of 10 mA cm−2, while a Tafel slope of 81.6 mV dec−1 in 1.0 M KOH showed the highest activity. The elevated photocatalytic hydrogen generation and improved HER performance of the developed catalysts signify a synergistic effect resulting from the junction and the Z-scheme charge transfer mechanism between the ZIF-67 and BFO nanomaterials. This introduces the BFO-ZIF composite as an efficient photocatalyst and electrocatalyst for hydrogen generation and evolution reaction.

Enhancing oxygen reduction reaction performance through eco-friendly chitosan gel-assisted molten salt strategy: Small NiCo alloy nanoparticles decorated with high-loading single Fe-NX

We developed an effective and eco-friendly strategy using chitosan gel-molten salt to achieve high loading (2.23 At. %) of single Fe-NX as assistive active sites. These sites were combined with small NiCo alloy NPs distributed on porous carbon aerogels to boost the ORR performance. The FeSAs-NiCo alloy@N-C sphere exhibits exceptional mass activity and specific activity of 3.705 A.mg−1 and 8.79 mA.cm−2(ECSA), respectively, at 0.85 V versus RHE. It has a superior onset potential of 1.08 V versus RHE, surpassing that of its nanoparticle Fe counterpart and NiCo alloy@N-C sphere. The significant improvement in ORR performance of the FeSAs-NiCo alloy@N-C sphere could be attributed to the positive effects of increased lattice strain due to the single atoms of Fe-NX hybridized with small NiCo alloy NPs. The chitosan gel-assisted molten salt strategy and assistive active sites of Fe-NX hybridized with NiCo alloy NPs regulate the electronic properties of the FeSAs-NiCo alloy@N-C sphere, both geometrically via lattice strain mismatch and electronically through shifting of the d-band center. This could influence the binding energies for oxygen and/or oxygen reduction intermediate adsorption/desorption. The additional improvement in the ORR performance of the FeSAs-NiCo alloy@N-C sphere also benefits from having a lower electrochemical activation energy.

Superiority of CuSe as a non-nobel electrocatalyst among copper chalcogens for overall water splitting reactions

Among the transition metals copper is one of the cheapest earth- abandoned elements which can enhance electrocatalytic activity. The Cu-based catalysts are superior for catalytic performance and stability in alkaline media for oxygen evolution reaction (OER) and exhibit high activity in acidic media for hydrogen evolution reaction (HER).Synthesized CuSe nanoparticle is found as the most efficient bifunctional electrocatalyst among the synthesized Cu chalcogenides for water splitting reaction. Electrocatalytic performance for water oxidation was investigated in alkaline solution1(M) KOH for OER and 0.5 (M) H2SO4 for HER. To achieve 10 mA/cm2, it was observed an over potential (mV) of 343 for OER and 126 for HER, which are much smaller than these of CuS (385,320) and CuO (410, 345) studied. In this article, we have elucidated some essential criteria need to be specified to evaluate the water splitting performance including onset potential, overpotential, Tafel slope, turnover frequency (TOF), and stability of the copper chalcogenide nanoparticles.

Amorphous metal-organic frameworks loaded on BiVO4 photoanodes with unique internal metal-like structure for promoting photoelectrochemical water splitting

Although ferrocene (Fc) based Metal-Organic Frameworks (MOFs) can act as oxygen evolution co-catalysts (OECs) for improvement of catalytic reactivity, the poor conductivity and lack of highly active metal sites limit its further application in photoelectrochemical (PEC) water splitting. Herein, the amorphous NiFc-MOF was grafted on BiVO4 photoanode (BiVO4@aNiFc-MOFs) for efficient PEC water splitting. This novel BiVO4@aNiFc-MOFs exhibits high current density of 4.34 mA cm−2 at 1.23 VRHE and relative low onset potential of 0.223 VRHE. The subsequent characterizations demonstrate that Ni species with metal-like state in bulk of aNiFc-MOFs form strong metal-support interaction with BiVO4, thereby promoting the interfacial charge transfer. Moreover, the surface of aNiFc-MOFs is short-range ordered with abundant coordinatively unsaturated Ni sites, creating a more favorable pathway for oxygen evolution reaction from thermodynamics. This work provides a simple method to design photoanodes with efficient OECs of amorphous MOFs for feasible PEC water splitting application.

Are (100) facets of transition metal carbonitrides suitable as electrocatalysts for nitrogen reduction to ammonia at ambient conditions?

Sustainable and energy-efficient ammonia production requires facile nitrogen reduction for hydrogen preservation and inorganic fertilizers. A nitrogen reduction apparatus with optimal stability, selectivity, and activity for ambient temperatures and pressure is needed to catalyze ammonia synthesis. This paper describes the investigation of using transition metal carbonitrides as catalyst to reduce molecular nitrogen electrochemically to NH3 at room temperature and atmospheric pressure. Density functional theory calculations determine the competition among associative, dissociative, and Mars-van Krevelen mechanisms where in most cases the Mars-van Krevelen is a more favorable reaction pathway. VCN and NbCN are the best candidates for ammonia production via the Mars-van Krevelen mechanism at low onset potentials of −0.52 V and −0.53 V vs reversible hydrogen electrode on the (100) facets. These carbonitrides are predicted to favor nitrogen reduction reaction rather than hydrogen evolution reaction.

Positive Electronic Nickel Active Site Enhances N─H/C─H Bonds Breaking for Electrooxidation of Amines to Nitriles Coupling with Hydrogen Production

AbstractElectrocatalytic conversion of amines to nitriles can be used as biomass upgrading to assist hydrogen production in water electrolysis. However, achieving efficient N─H/C─H bond breaking in amines oxidation remains a challenge. Herein, the nitrogen‐doped carbon supported NiO nanoparticles with positive electronic nickel active site are simply synthesized to achieve ∽99% selectivity and complete conversion in electrooxidizing amines to nitriles, and the onset potential of the whole reaction is as low as 1.32 V vs. RHE. Detailed in situ characterizations and theoretical calculations prove that the carbon substrate enhances the interaction between the N 2p orbital of amines and the Ni 3d orbital, which favors the construction of an indirect oxidation intermediate state R‐CH2NH2···NiO(OH)abs and  promotes the subsequent stepwise dehydrogenation to nitriles. This whole reaction produces 16.4 times more hydrogen than pure water splitting, facilitating the development of the chemicals industry and energy utilization.

A Comprehensive Review of Bimetallic Nanoparticle–Graphene Oxide and Bimetallic Nanoparticle–Metal–Organic Framework Nanocomposites as Photo-, Electro-, and Photoelectrocatalysts for Hydrogen Evolution Reaction

This review extensively discusses current developments in bimetallic nanoparticle–GO and bimetallic nanoparticle–MOF nanocomposites as potential catalysts for HER, along with their different synthesis methodologies, structural characteristics, and catalytic mechanisms. The photoelectrocatalytic performance of these catalysts was also compared based on parameters such as Tafel slope, current density, onset potential, turnover frequency, hydrogen yield, activation energy, stability, and durability. The review shows that the commonly used metal alloys in the bimetallic nanoparticle–GO-based catalysts for HERs include Pt-based alloys (e.g., PtNi, PtCo, PtCu, PtAu, PtSn), Pd-based alloys (e.g., PdAu, PdAg, PdPt) or other combinations, such as AuNi, AuRu, etc., while the most used electrolyte sources are H2SO4 and KOH. For the bimetallic nanoparticle MOF-based catalysts, Pt-based alloys (e.g., PtNi, PtCu), Pd-based alloys (e.g., PdAg, PdCu, PdCr), and Ni-based alloys (e.g., NiMo, NiTi, NiAg, NiCo) took the lead, with KOH being the most frequently used electrolyte source. Lastly, the review addresses challenges and prospects, highlighting opportunities for further optimization and technological integration of the catalysts as promising alternative photo/electrocatalysts for future hydrogen production and storage.

Excellent Photoelectro-Catalytic Performance of In2S3/NiFe-LDH Prepared by a Two-Step Method

In this work, we synthesize hierarchical In2S3/NiFe-layered double hydroxide (In2S3/NiFe-LDH) nanoarrays on an F-doped SnO2 glass substrate via a two-step method, which the In2S3 electrode film was firstly prepared using chemical bath deposition on F-doped SnO2 glass substrate, and then the layered NiFe-LDH was deposited on In2S3 electrode film by hydrothermal synthesis. The two-component photoanode In2S3/NiFe-LDH exhibits significantly enhanced photoelectrochemical properties compared with the In2S3 single-component; due to that, the NiFe-LDH nanosheets depositing on the surface of In2S3 nanocrystal can reduce the accumulation of photogenic holes, facilitate the separation of photogenerated charge carriers, and enhance the light response and absorption. After being decorated with the NiFe-LDH nanosheets, the In2S3/NiFe-LDH photoanode displays a lower onset potential of 0.06 V and an enhanced photocurrent density as high as 0.30 mA·cm−2 at the potential of 1.0 V (vs. RHE). Furthermore, it also displays a 90% degradation rate of xylose oxidizing into xylose acid in 3 h under UV light. This work provides a promising approach for designing new heterojunctions applied to biomass degradation.