Stable Electrocatalysts Research Articles

Amorphous CoFePOx hollow nanocubes decorated with g-C3N4 quantum dots to achieve efficient electrocatalytic performance in the oxygen evolution reaction.

Simultaneously enriching active sites and enhancing intrinsic activity in a simple way is of great importance for the design of highly active electrocatalysts for the oxygen evolution reaction (OER), but it still faces challenges. Herein, g-C3N4 quantum dot decorated amorphous hollow CoFe bimetallic phosphate nanocubes (a-CoFePOx@CNQD) are prepared as an efficient OER electrocatalyst by a simple in situ etching-phosphating process. Research shows that their unique hollow architecture and amorphous structure can help provide generous exposed active sites for OER, and the incorporation of g-C3N4 quantum dots can effectively adjust the electronic structure to improve the intrinsic activity. Therefore, a-CoFePOx@CNQD exhibits excellent OER performance with a low overpotential (239 mV) at 10 mA cm-2 and a small Tafel slope (58.4 mV dec-1), surpassing the commercial RuO2. Furthermore, a-CoFePOx@CNQD as an electrode catalyst for a water electrolyzer and zinc-air battery also shows higher performance and stability than RuO2 + Pt/C catalysts. This study provides a feasible strategy for preparing efficient and stable amorphous hollow heterostructure OER electrocatalysts.

Cobalt Nitride-Implanted PtCo Intermetallic Nanocatalysts for Ultrahigh Fuel Cell Cathode Performance.

Stable and active oxygen reduction electrocatalysts are essential for practical fuel cells. Herein, we report a novel class of highly ordered platinum-cobalt (Pt-Co) alloys embedded with cobalt nitride. The intermetallic core-shell catalyst demonstrates an initial mass activity of 0.88 A mgPt-1 at 0.9 V with 71% retention after 30,000 potential cycles of an aggressive square-wave accelerated durability test and loses only 9% of its electrochemical surface area, far exceeding the US Department of Energy 2025 targets, with unprecedented stability and only a minimal voltage loss under practical fuel cell operating conditions. We discover that regulating the atomic ordering in the core results in an optimal lattice configuration that accelerates the oxygen reduction kinetics. The presence of cobalt nitride decorated within PtCo superlattices guarantees a larger barrier to Co dissolution, leading to the excellent endurance of the electrocatalysts. This work brings up a transformative structural engineering strategy for rationally designing high-performing Pt-based catalysts with a unique atomic configuration for broad practical uses in energy conversion technology.

Boosting Hydrogen Evolution Behaviors of Porous Nickel Phosphate by Phosphorization Engineering

A stable and efficient porous nickel phosphate (p-NiPO/Ti) electrocatalyst on titanium sheets was developed via electrochemical deposition and low-temperature phosphatization. For obtaining the optimal performance of the p-NiPO/Ti electrocatalyst, the optimized experimental parameters of deposition and phosphatization were determined by parallel experiments. After the preparation, XPS and XRD were used to validate the chemical and amorphous structure, with SEM and TEM simultaneously validating a distinct nanosheet/nanocluster crosslinked microstructure. In particular, with phosphatization conditions maintained at 300 °C for 10 min, the p-NiPO/Ti produced demonstrated excellent charge transfer and catalytic characteristics in 1.0 M KOH. The electrocatalytic results revealed that the optimal p-NiPO/Ti with excellent catalytic performance and excellent stability (~24 h) needs lower HER overpotentials (128 mV at 10 mA cm−2 and 242 mV at 100 mA cm−2) as inputs. This research provides a promising strategy with which to use transition metal materials as catalysts in alkaline electrocatalytic hydrogen production.

Transforming Prussian Blue Analogues: The Future-Centric Pathway to Rise of Thin Layered Double Hydroxides for Superior Water Oxidation: An Overview

Prussian blue analogues (PBAs)[1–5] have exhibited great performance towards electrochemical water oxidation because of their high activity and stability. However, there were some challenges because of their limited surface area and less accessible active sites. Herein this work, we have explored the synthesis of a Prussian blue analogue-based thin layered double hydroxide (PBA-TLDH)[6–9] through a reconstruction method. The (PBA-TLDH) possessed high surface area and a large number of active sites for enhanced electrochemical water oxidation. These PBA-LDH materials were well characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and electrochemical techniques[1,7,10–12]. The PBA-TLDH materials had a well-defined thin layered structure with the PBAs uniformly distributed in the interlayer spaces of the LDHs. The PBA-LDH catalyst showed enhanced electrocatalytic activity towards water oxidation, with a very low overpotentials up to 240 mV and current density of 10 mA cm-2,[9,13–16] have been achieved which is significantly lower than that of the pristine PBAs. Moreover, these thin layered double hydroxides material showed excellent stability over large electrochemical cycle. This work provides a new strategy for the design and synthesis of highly active and stable electrocatalysts for water oxidation.

Phase Reconstruction‐Directed Synthesis of Oxalate‐Functionalized Nickel Hydroxide Electrocatalyst for High‐Yield H2O2 Generation at Industrial Currents

AbstractThe electrochemical oxygen reduction reaction (2e− ORR) offers a promising approach for H2O2 production, yet developing highly active, selective, and stable electrocatalysts remains a challenge. In this work, a phase reconstruction strategy is presented to synthesize an oxalate‐adsorbed nickel hydroxide electrocatalyst (Ni(OH)2‐C2O4) through the self‐dissociation of nickel oxalate in an alkaline medium, leading to a notable enhancement in H2O2 yield at elevated current densities. Remarkably, Ni(OH)2‐C2O4 exhibits a 2e− selectivity exceeding 93% across a broad voltage range (0.0 to 0.5 V vs RHE) in 0.1 M KOH, outperforming pristine Ni(OH)2. When deployed as a gas diffusion electrode in a flow cell, the Ni(OH)2‐C2O4 catalyst demonstrates stable operation for 50 h at 200 mA cm−2, with a Faradaic efficiency surpassing 90% and a peak H2O2 yield of 6.2 mol g−1cat h−1. Comprehensive advanced characterizations, including in situ Raman spectroscopy, transient photovoltage spectra, and transient potential scanning spectra, coupled with post‐ORR analyses, reveal that surface‐adsorbed oxalate groups on Ni(OH)2 enhance the interfacial reaction kinetics between active Ni sites and reactants by inducing a charge trapping effect and forming a hydrogen‐bonded network, facilitating robust and high‐yield H2O2 production.

Boosting Zn-air battery performance: Fe single-atom anchored on F, N co-doped carbon nanosheets for efficient oxygen reduction

Sluggish oxygen reduction reaction (ORR) kinetics limit the development of metal-air batteries and fuel cells, hindering overall energy conversion efficiency. Therefore, significant research has focused on cost-effective, highly active, and exceptionally stable non-precious metal ORR electrocatalysts. This study presents the synthesis of a nanohybrid material called Fe SAs/FN-CNs. It is made up of single iron atoms embedded in ultrathin porous carbon nanosheets that are co-doped with F and N. The synthesis process involves an easy one-step pyrolysis technique without additional post-treatment. The Fe SAs/FN-CNs material is designed to function as an effective zinc-air battery ORR electrocatalyst. Based on their distinctive components and structure, the optimal Fe SAs/FN-CNs exhibit outstanding catalytic efficiency and long-lasting performance in the alkaline ORR. They have an onset potential (Eonset) of 0.95 V, a half-wave potential (E0.5) of 0.85 V, a kinetic current density (JK) of 20.49 mA cm−2 at 0.8 V, and a diffusion-limited current (Jd) of 6.2 mA cm−2. In addition, a Zn-air battery made using homemade Fe SAs/FN-CNs demonstrated a power density of 197 mW cm−2, a specific capacitance of 813.5 mAh g−1, and exceptional stability. It outperformed the commercial Pt/C by operating continuously for over 147 hours at 10 mA/cm² (discharge-charge). The Fe SAs/FN-CNs nanohybrid electrocatalyst shows great potential as an electrocatalyst for various metal-air batteries.

Iron phosphide nanoparticles anchored on 3D nitrogen-doped graphene as an efficient electrocatalysts for hydrogen evolution reaction in alkaline media

Electrocatalysts play a crucial role in hydrogen evolution reaction (HER), facilitating a clean and sustainable generation of hydrogen energy. To promote the HER process, it is imperative to employ highly efficient, stable, and cost-effective electrocatalysts. This research focuses on the design of iron phosphide nanoparticles anchored onto a porous three-dimensional nitrogen-doped graphene (FeP@3DNG). The porous framework of 3DNG serves a multifaceted purpose: it prevents the aggregation of FeP nanoparticles during phosphidation, safeguards the FeP electrocatalyst from oxidation during the HER, and simultaneously enhances electrical conductivity and stability. Notably, the FeP@3DNG nanocomposite demonstrated the efficient activity and highest HER activity with an overpotential of 76 mV to achieve 10 mA cm−2 and a small Tafel slope of 40.2 mV dec−1 as well as good long-term durability for 20 h in 1.0 M KOH solution. The high performance of the FeP@3DNG nanocomposite can be primarily corresponded to the synergistic effects of the highly active of FeP nanoparticles and advantages of porous three-dimensional graphene with excellent electrocatalytic activity, high specific surface area, and chemical stability, thus, resulting in the improvement the overall electrocatalytic activity.

CoFe2O4 with the In-Situ Formed Oxygen Vacancies and Co Particles as an Efficient Bifunctional Catalyst for Rechargeable Zinc-Air Batteries.

Rechargeable zinc-air batteries (RZABs) are considered as one of the most promising clean energy device due to their abundant resources, low cost and environmental friendliness. However, their energy efficiency and cycle life are far from satisfactory due to the poor activity and stability of bi-functional electrocatalyst in air cathode. In this work, an efficient bi-functional catalyst (rGO-CoFe2O4/Co) was derived from its precursor (rGO-CoFe2O4) through a simple annealing process. Electrochemical measurements prove that rGO-CoFe2O4/Co with the in-situ formed Co nano particles and rich oxygen vacancies appears excellent oxygen reduction reaction and oxygen evolution reaction catalytic activity compared to its counterpart. Its half-wave potential is 0.81 V (vs RHE) and the OER overpotential is only 310 mV (vs RHE). In addition, rechargeable zinc-air batteries assembled with rGO-CoFe2O4/Co show the highest peak power density (128.9 mW cm-2) and cycling stability compared to rGO-CoFe2O4 and commercial Pt/C-RuO2 catalysts. This work provides a simple strategy for the design of advanced bifunctional catalysts.

Interface Synergistic Effect of NiFe-LDH/3D GA Composites on Efficient Electrocatalytic Water Oxidation.

Currently, NiFe-LDH exhibits an excellent oxygen evolution reaction (OER) due to the interaction of the two metal elements on the layered double hydroxide (LDH) platform. However, such interaction is still insufficient to compensate for its poor electrical conductivity, limited number of active sites and sluggish dynamics. Herein, a feasible two-step hydrothermal strategy that involves coupling low-conductivity NiFe-LDH with 3D porous graphene aerogel (GA) is proposed. The optimized NiFe-LDH/GA (1:1) produced possesses a 257 mV (10 mA cm-2) overpotential and could operate stably for 56 h in an OER. Our investigation demonstrates that the NiFe-LDH/GA has a three-dimensional mesoporous structure, and that there is synergistic interaction between LDH and GA and interfacial reconstruction of NiOOH. Such an interface synergistic coupling effect promotes fast mass transfer and facilitates OER kinetics, and this work offers new insights into designing efficient and stable GA-based electrocatalysts.

Synergistic Effect of Cobalt/Ferrocene as a Catalyst for the Oxygen Evolution Reaction.

There is a great deal of interest in the development of electrocatalysts for the oxygen evolution reaction (OER) that are stable and have high activity because this anodic half-reaction is the main bottleneck in water splitting and other key technologies. Cobalt and iron oxide and oxyhydroxide electrocatalysts constitute a cheaper alternative to the highly active and commonly used Ir- and Ru-based catalysts. Most of the described electrocatalysts require tedious synthetic and expensive preparation procedures. We report here a facile and straightforward preparation of an electrocatalyst by a combination of commercial compounds, such as cobalt chloride and ferrocene. A highly active and stable OER electrocatalyst is obtained, which shows a low overpotential in the alkaline medium as a consequence of a synergistic effect between both compounds and is inexpensive.

Recent development of non‐iridium‐based electrocatalysts for acidic oxygen evolution reaction

AbstractProton exchange membrane water electrolyser (PEMWE) possesses great significance for the production of high purity of hydrogen. To expedite the anodic oxygen evolution reaction (OER) that involved multiple electron–proton‐coupled process, efficient and stable electrocatalysts are highly desired. Currently, noble‐metal Ir‐based materials are the benchmark anode due to its corrosion‐resistant property and favourable combination of activity/stability. However, the large‐scale deployment of PEMWE is usually constrained due to the use of the scarcest element iridium. In this review, we disclose the current research progress towards the non‐iridium‐based electrocatalysts for OER in acidic media, and then summarize some typical oxides that possesses good catalytic performance. Besides, we also present the unresolved problems and challenges in an attempt to enhance the activity/stability of these catalysts.

Ligand engineering towards electrocatalytic urea synthesis on a molecular catalyst

Electrocatalytic C-N coupling from carbon dioxide and nitrate provides a sustainable alternative to the conventional energy-intensive urea synthetic protocol, enabling wastes upgrading and value-added products synthesis. The design of efficient and stable electrocatalysts is vital to promote the development of electrocatalytic urea synthesis. In this work, copper phthalocyanine (CuPc) is adopted as a modeling catalyst toward urea synthesis owing to its accurate and adjustable active configurations. Combining experimental and theoretical studies, it can be observed that the intramolecular Cu-N coordination can be strengthened with optimization in electronic structure by amino substitution (CuPc-Amino) and the electrochemically induced demetallation is efficiently suppressed, serving as the origination of its excellent activity and stability. Compared to that of CuPc (the maximum urea yield rate of 39.9 ± 1.9 mmol h−1 g−1 with 67.4% of decay in 10 test cycles), a high rate of 103.1 ± 5.3 mmol h−1 g−1 and remarkable catalytic durability have been achieved on CuPc-Amino. Isotope-labelling operando electrochemical spectroscopy measurements are performed to disclose reaction mechanisms and validate the C-N coupling processes. This work proposes a unique scheme for the rational design of molecular electrocatalysts for urea synthesis.

Regulating Ru-O Bond and Oxygen Vacancies of RuO2 by Ta Doping for Electrocatalytic Oxygen Evolution in Acid Media.

Proton exchange membrane water electrolysis (PEMWE) is considered an ideal green hydrogen production technology with promising application prospects. However, the development of efficient and stable acid electroanalytic oxygen electrocatalysts is still a challenging bottleneck. This progress is achieved by adopting a strategic approach with the introduction of the high valence metal Ta to regulate the electronic configuration of RuO2 by manipulating its local microenvironment to optimize the stability and activity of the electrocatalysts. The Ta-RuO2 catalysts are notable for their excellent electrocatalytic activity, as evidenced by an overpotential of only 202 mV at 10 mA cm-2, which significantly exceeds that of homemade RuO2 and commercial RuO2. Furthermore, the Ta-RuO2 catalyst exhibits exceptional stability with negligible potential reduction observed after 50 h of electrolysis. Theoretical calculations show that the asymmetric configuration of Ru-O-Ta breaks the thermodynamic activity limitations usually associated with adsorption evolution, weakening the energy barrier for the formation of the OOH* formation. The strategic approach presented in this study provides an important reference for the development of a stable active center for acid water splitting.

High-Entropy Selenides with Tunable Lattice Distortion as Efficient Electrocatalysts for Oxygen Evolution Reaction.

Developing stable and active electrocatalysts is crucial for enhancing the oxygen evolution reaction (OER) efficiency, which sluggish kinetics hinders sustainable hydrogen production. High entropy selenides (HESes) features with random distribution of multiple metals cations and unique electronic and size effect of Se anion, allowing for precious regulation of their catalytic properties towards high OER activity. In this work, we report a series of high-entropy selenides catalysts with tunable lattice strain for electrocatalytic oxygen evolution. Electrochemical measurements show that the quinary (NiCoMnMoFe)Sex requires only 291 mV to reach 10 mA cm-2 and exhibits a superior stability with negligible current decay during 100 h's continuous operation. By combining experimental measurements and theoretical calculation, the study reveals that the lattice distortion, reflected by the local microstrain near the active site, plays a vital role in boosting the OER activity of HESes.

Strontium Doped IrOx Triggers Direct O-O Coupling to Boost Acid Water Oxidation Electrocatalysis.

The discovery of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) in acidic conditions is crucial for the commercialization of proton-exchange membrane water electrolyzers. In this work, we propose a Sr(OH)2-assisted method to fabricate a (200) facet highly exposed strontium-doped IrOx catalyst to provide available adjacent iridium sites with lower Ir-O covalency. This design facilitates direct O-O coupling during the acidic water oxidation process, thereby circumventing the high energy barrier associated with the generation of *OOH intermediates. Benefiting from this advantage, the resulting Sr-IrOx catalyst exhibits an impressive overpotential of 207 mV at a current density of 10 mA cm-2 in 0.5 M H2SO4. Furthermore, a PEMWE device utilizing Sr-IrOx as the anodic catalyst demonstrates a cell voltage of 1.72 V at 1 A cm-2 and maintains excellent stability for over 500 hours. Our work not only provides guidance for the design of improved acidic OER catalysts but also encourages the development of iridium-based electrocatalysts with novel mechanisms for other electrocatalytic reactions.

Silver Nanowire Aerogel Support Promotes Stable Hydrogen Evolution Reaction at High Current Density.

The stability of electrocatalysts during the hydrogen evolution reaction (HER) is vital for efficient production of hydrogen energy. Herein, we demonstrate that silver nanowire aerogel-based support (AABS) could facilitate the construction of HER catalysts with extraordinary long-term stability. A full nanostructure catalyst of nickel phosphide based formed on AABS (Ni2P-Ni5P4@AABS) was prepared to achieve an overpotential of 687 mV (without iR compensation) for HER at the current density of 1 A cm-2 in 0.5 M H2SO4. Excitingly, the stable HER performance was kept for 42 days during the long-term stability (i-t) test at high current density (0.5-1 A cm-2). The excellent HER performance of the Ni2P-Ni5P4@AABS catalyst is attributed to rapid electron transport pathways, numerous more accessible active sites, and support induced enhanced catalytic activity. The support effect was highlighted by a proposed phenomenological two-channel model for electron transport, which provides fresh insights into the design strategy for energy storage and delivery.

Tuning the structure and properties of carbon cloth by FeCl3intercalation for efficient two-electron oxygen reduction catalysis.

The advancement of various energy conversion and storage technologies hinges on the development of efficient and stable electrocatalysts for the oxygen reduction reaction (ORR). In this study, we report the enhancement of carbon cloth (CC) for robust ORR through an FeCl3intercalation reaction. Utilizing a thermal annealing method, FeCl3was intercalated into the graphite structure on the surface of CC, resulting in the creation of numerous defects and the incorporation of Fe species. These newly introduced defects play a pivotal role in activating the ORR via a two-electron pathway. The presence of Fe species further stabilizes the catalytic activity, leading to efficient and stable ORR performance. Our findings highlight the significance of defect engineering and Fe species incorporation in carbon-based materials for improved ORR catalysis and pave the way for the development of advanced electrocatalysts for energy-related applications.

Smart utilization of bimetallic NiCo alloy supported carbon dots and sulfur quantum dots derived 3D nanocomposite for oxygen evolution reaction

The increasing demand for highly active and stable electrocatalysts for the oxygen evolution reaction (OER) in future energy-conversion systems has driven researchers to explore novel alternatives to Pt-based catalysts. Among these alternatives, zero-dimensional quantum dots have emerged as promising candidates due to their high surface area and intrinsic electrocatalytic activity, which lead to significant breakthroughs in electrocatalytic performance. Herein, we conducted a preliminary investigation into the application of bimetallic NiCo alloy deposited on metal-free quantum dots (carbon dots and sulfur quantum dots) derived nano sponge for the oxygen evolution reaction. The synthesized NiCo-CDs-800 exhibited remarkable electrocatalytic OER activity, achieving a current density of 10 mA cm−2 with only 221 mV overpotential, far surpassing commercial RuO2 electrocatalysts. The excellent electrocatalytic activity can be attributed primarily to high electrochemically active area (168.97 mF cm−2), the presence of large proportion of oxygen vacancies (68.61 %), rich pyridinic nitrogen structure (29.30 %) with strong water adsorption, and synergistic effect of bimetals as supported by density functional theory calculations. Meanwhile, the newly prepared NiCo-SQDs-700 under the similar procedure demonstrate a satisfied OER performance and competing stability when compared to NiCo-CDs. These findings open a new avenue for the application of metal free CDs and SQDs to the growing family of metal@QDs.

Construction of One-Dimensional Covalent-Organic Framework Coordinated with Main Group Metals for Selective Electrochemical Synthesis of H2O2.

Covalent-organic frameworks (COFs) are promising electrocatalysts for the selective synthesis of H2O2 through the two-electron oxygen reduction reaction (2e- ORR). However, the design and synthesis of efficient and stable COF-based electrocatalysts is still challenging. In this work, a predesigned 1,10-phenanthroline-based one-dimensional COF (PYTA-PTDE-COF) was constructed to anchor main group metal (In, Sn, and Sb) as electrocatalysts toward 2e- ORR. The catalysts are featured with fully exposed metalated side chains. Structural characterization revealed that PYTA-PTDE-M's (M = In, Sn, and Sb) are all quite similar, except for the coordinated metal ions with the maintenance of good crystallinity. They all exhibited satisfying activity and selectivity toward 2e- ORR under alkaline conditions. Among them, PYTA-PTDE-Sb exhibited the best performance (Eonset is 0.765 V, the H2O2 selectivity is 96%, and the yield rate is 209.2 mmol gcat-1 h-1). Moreover, it also delivered superior stability with almost no attenuation of current density during the long-time test. Theoretical calculations revealed that the Sb metal site in the COFs has the lowest adsorption strength of *OOH, which could be the main reason for its superior selectivity. The PYTA-PTDE-Sb assembled zinc-air battery realizes not only the supply of clean energy but also the production of green chemicals, showing it is highly promising in practical applications. This work offers an example for designing main group metal-coordinated 1D COFs and reveals fundamental structure-activity relationship toward 2e- ORR.

Unveiling active sites in FeOOH nanorods@NiOOH nanosheets heterojunction for superior OER and HER electrocatalysis in water splitting

The development of cost-effective, highly active, and stable electrocatalysts for water splitting to produce green hydrogen is crucial for advancing clean and sustainable energy technologies. Herein, we present an innovative in-situ synthesis of FeOOH nanorods@NiOOH nanosheets on nickel foam (FeOOH@NiOOH/NF) at an unprecedentedly low temperature, resulting in a highly efficient electrocatalyst for overall water splitting. The optimized FeOOH@NiOOH/NF sample, evaluated through time-dependent studies, exhibits exceptional oxygen evolution reaction (OER) performance with a low overpotential of 261 mV at a current density of 20 mA cm−2, alongside outstanding hydrogen evolution reaction (HER) activity with an overpotential of 150 mV at a current density of 10 mA cm−2, demonstrating excellent stability in alkaline solution. The water-splitting device featuring FeOOH@NiOOH/NF-2 electrodes achieves a voltage of 1.59 V at a current density of 10 mA cm−2, rivalling the state-of-the-art RuO2/NF||PtC/NF electrode system. Density functional theory (DFT) calculations unveil the efficient functionality of the Fe sites within the FeOOH@NiOOH heterojunction as the active OER catalyst, while the Ni centres are identified as the active HER sites. The enhanced performance of OER and HER is attributed to the tailored electronic structure at the heterojunction, modified magnetic moments of active sites, and increased electron density in the dx2-y2 orbital of Fe. This work provides critical insights into the rational design of advanced electrocatalysts for efficient water splitting.