High-entropy Alloy Nanoparticles Research Articles

Regulating the electronic modulation configuration of MnxFeCoNiCu high entropy alloy for reliable sulfur redox kinetics

Current research on sulfur redox catalysis primarily focuses on the adsorption and catalytic conversion of lithium polysulfides (LiPSs). However, it often neglecting the modulation of the catalysts' electronic structure, which includes charge transfer and orbital interactions that significantly affect adsorption and catalytic properties. In this work, multi-channel carbon nanotubes modified with high entropy alloy nanoparticles (MnxFeCoNiCu/MCCFs) are elaborately synthesized as hosts to reveal the relationship between the catalytic activity and surface electronic configuration for reliable sulfur electrochemistry. Combining density functional theory (DFT) calculations with detailed experimental investigations, we demonstrate that modulating the electron consumption center of this intrinsic electron transfer-replenishment mechanism, the surface charge distribution is reestablished, thereby improving the performance of multi-electron reactions. Achieving a balance between adsorption and desorption significantly enhance the catalytic efficiency for LiPSs conversion. Consequently, the as-prepared Mn1.00/MCCFs with an optimized electronic structure as sulfur host can deliver a high capacity of 938 mAh g−1, corresponding to an ultralow capacity decay of 0.013 % per cycle over 500 cycles at 1.0 C.

Microenvironment regulation to synthesize sub-3 nm Pt-based high-entropy alloy nanoparticles enabling compressed lattice to boost electrocatalysis

Platinum (Pt) is inevitably employed to facilitate various electrocatalysis including hydrogen oxidation/evolution and oxygen reduction reactions (HOR/HER/ORR), the foundation for renewable energy conversion and storage. Pt-based high-entropy-alloy (HEA) catalysts have been recently presenting promises to improve intrinsic activity of unit mass Pt. However, their current synthesis methods always produce large particles—some can control small size but have to use complicated recipe and/or highly toxic and expensive chemicals. Alternatively, a facile microenvironment regulation strategy is herein proposed to tune solvent polarity and nanoparticle-support interactions within the precursors for carbon-thermal shock pyrolysis. We found that the decreased solvent polarity and enhanced particle-support affinity can jointly control the nanoparticle size ultimately to ~2.68nm with ~10wt % Pt loading. The compressed lattice fringe in such HEA particles leads to electron accumulation at Pt atoms and build a moderate charge density rearrangement, showing superior multifunctional HER/HOR/ORR activity to Pt/C in acidic media.

"One-Stone, Two-Birds": Zinc-Rich Metal-Organic Frameworks as Precursors for High-Entropy Zn-Air Battery Electrocatalysts with Hierarchical Pore Structures.

The active sites of inexpensive transition metal electrocatalysts are sparse and singular, thus high-entropy alloys composed of non-precious metals have attracted considerable attention due to their multi-component synergistic effects. However, the facile synthesis of high-entropy alloy composites remains a challenge. Herein, we report a "one-stone, two-birds" method utilizing zinc (Zn)-rich metal-organic frameworks as precursors, by virtue of the low boiling point of Zn (907 °C) and its high volatility in alloys, high-entropy alloy carbon nanocomposite with a layered pore structure was ultimately synthesized. The experimental results demonstrate that the volatilization of zinc can prevent metal agglomeration and contribute to the formation of uniformly dispersed high-entropy alloy nanoparticles at slower pyrolysis and cooling rates. Simultaneously, the volatilization of Zn plays a crucial role in creating the hierarchically porous structure. Compared to the zinc-free HEA/NC-1, the HEA/NC-5 derived from the precursor containing 0.8 Zn exhibit massive micropores and mesopores. The resulting nanocomposites represent a synergistic effect between highly dispersed metal catalytic centers and hierarchical adsorption sites, thus achieving excellent electrocatalytic oxygen reduction performance with low catalyst loading compared to commercial Pt/C. This convenient zinc-rich precursor method can be extended to the production of more high-entropy alloys and various application fields.

High Entropy Induced Local Charge Enhancement Promotes Frank–Van der Merwe Growth for Dendrite‐Free Potassium Metal Batteries

AbstractPotassium metal batteries (PMBs) are promising for next‐generation energy storage. However, the high reactivity of the anode causes instability in the solid electrolyte interface (SEI), resulting in Volmer‐Weber (V‐W) type deposition. To achieve uniform Frank‐van der Merwe (F‐M) type deposition, high entropy alloy nanoparticles are designed (HEA NPs) with equimolar ratios of Mn, Fe, Co, Cu, and Ni to enhance the substrate‐K metal interface. HEA NPs enhance the K affinity of the N‐doped nanocarbon fiber substrate (N‐PCNF) and maximize ion and electron transport efficiency. The dendrite‐free horizontal growth of K metal confirmed through Operando X‐ray diffraction (XRD) and optical microscopy (OM). Consequently, the asymmetric cell exhibits ultra‐long cycling stability of 2350 hours at a high current density of 8 mA cm−2. The full cell composed of molten K diffusion into HEA NPs decorated N‐PCNF anode with perylene‐3,4,9,10‐tetracarboxylic dianhydride cathode (HEA‐N‐PCNF‐K||PTCDA) delivers an energy density of 331 W h kg−1 and remains stable over 2000 cycles. This study offers a promising pathway for innovative PMBs designs with broad application prospects.

High electromagnetic wave absorption performance from all-scale hierarchically defective Ni-Mn-Co-Cu-Al high entropy alloys@carbon

All-scale hierarchical defects induced by structural designing from unit cell to mesoscale play a significant role in oscillating and dissipating electromagnetic wave energy under external microwave radiation. To construct such all-scale hierarchical defects, hereby, high-entropy alloy nanoparticles coated by microscale carbon (HEA@C) with a core–shell structure were obtained by carbonizing Ni-Mn-Co-Cu-Al metal–organic. Thus, all-scale hierarchical defects were gained, including lattice distortion and nanotwins caused by the high entropy effect, vacancy and topological defects within carbon, and the heterojunction between high entropy nanoparticles and carbon. These all-scale hierarchical defects combined with the magnetic and conductive nature of HEA@C enable us to achieve a high electromagnetic wave absorption performance, with a reflection loss (RLmin) value of −52.36 dB and an effective absorption bandwidth (EAB) of 5.01 GHz. It implies that HEA@C should be an effective electromagnetic wave (EMW) absorber.

Laser solid-phase synthesis of graphene shell-encapsulated high-entropy alloy nanoparticles

Rapid synthesis of high-entropy alloy nanoparticles (HEA NPs) offers new opportunities to develop functional materials in widespread applications. Although some methods have successfully produced HEA NPs, these methods generally require rigorous conditions such as high pressure, high temperature, restricted atmosphere, and limited substrates, which impede practical viability. In this work, we report laser solid-phase synthesis of CrMnFeCoNi nanoparticles by laser irradiation of mixed metal precursors on a laser-induced graphene (LIG) support with a 3D porous structure. The CrMnFeCoNi nanoparticles are embraced by several graphene layers, forming graphene shell-encapsulated HEA nanoparticles. The mechanisms of the laser solid-phase synthesis of HEA NPs on LIG supports are investigated through theoretical simulation and experimental observations, in consideration of mixed metal precursor adsorption, thermal decomposition, reduction through electrons from laser-induced thermionic emission, and liquid beads splitting. The production rate reaches up to 30 g/h under the current laser setup. The laser-synthesized graphene shell-encapsulated CrMnFeCoNi NPs loaded on LIG-coated carbon paper are used directly as 3D binder-free integrated electrodes and exhibited excellent electrocatalytic activity towards oxygen evolution reaction with an overpotential of 293 mV at the current density of 10 mA/cm2 and exceptional stability over 428 h in alkaline media, outperforming the commercial RuO2 catalyst and the relevant catalysts reported by other methods. This work also demonstrates the versatility of this technique through the successful synthesis of CrMnFeCoNi oxide, sulfide, and phosphide nanoparticles.

Rapidly synthesizing magneto-thermal adjustable high entropy alloy nanoparticles on carbon fiber surface for enhancing electromagnetic wave absorption, thermal conductivity and interface compatibility of composites

It is a significant challenge to develop a fast carbon fiber (CF) surface modification method that could generate a simple multifunctional CF surface, especially in the field of electromagnetic wave (EMW) and thermal regulation. Herein, the FeCoNiAlMn high-entropy alloy (HEA) nanoparticles modified CF (HEA-CF) was successfully prepared by microwave induced carbon thermal shock (MCTS) in a few seconds. The HEA-CF possessed magneto-thermal adjustability by controlling the elemental composition and crystal structures of HEA nanoparticles. It exhibited outstanding dielectric-magnetic loss and phonon heat transfer capability. Moreover, HEA nanoparticles and cellulose nanofibers on CF surface also formed multiscale interfacial reinforced structure. Consequently, HEA-CF/Polyamide 6 (PA6) composites demonstrated extraordinary versatility. MCTS5s-CF/PA6 exhibited the strongest absorption with minimum reflection loss value of −63.6 dB at 2.4 mm thickness. The maximum effective absorption bandwidth reached 6.67 GHz with thickness of only 1.9 mm. Compared with that of untreated-CF/PA6 composite, the thermal conductivities of MCTS4s-CF and MCTS5s-CF/PA6 composites increased by 45.2 % and 19.1 %. Simultaneously, the tensile strength of MCTS4s-CF/PA6 and MCTS5s-CF/PA6 composites increased by 19.5 % and 16.1 %. This new approach provided an effective way to realize multifunctional composites. Its low-cost, efficient and environmentally friendly process had great potential for large-scale production.

Atomic Structure Amorphization and Electronic Structure Reconstruction of FeCoNiCrMox High-Entropy Alloy Nanoparticles for Highly Efficient Water Oxidation.

The complexity of the multielement interaction in high-entropy alloys (HEAs) may provide more active sites to adapt different catalytic reaction steps in oxygen evolution reaction (OER). Investigating the correlation between structure and performance of HEAs electrocatalysts is both essential and challenging. In this work, FeCoNiCrMox HEAnanoparticles are successfully fabricated utilizing a unique nanofabrication method called inert gas condensation. With the increase of high-valence metal component Mo, the atomic structure amorphization and electronic structure reconstruction are unveiled. According to the X-ray photoelectron spectroscopy valence spectra, the d-band center of FeCoNiCrMox is ascending, and thus enhancing the adsorption energy. Synchrotron pair distribution function analysis reflects the degree of structural disorder and reveals a robust correlation with the intrinsic OER activities of the electrocatalysts. FeCoNiCrMo1.0 high-entropy metallic glass nanoparticles exhibit an outstanding OER performance with an ultralow overpotential of 294.5mV at a high current density of 100mAcm-2. This work brings fundamental and practical insights into the modulation mechanism of metal components of HEAs catalysts for developing OER.

High Entropy Alloys as Bifunctional Catalysts for Reversable Metal Air Batteries

The development of stable non-noble metal bifunctional catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are essential for technologies such as reversible metal air batteries. We have shown that synthesis of high entropy alloy nanoparticles formed through a novel synthesis method where metal precursor containing aqueous nanodroplets freely diffusing in an emulsion solution, collide with an electrode surface and the metal precursors are reduced, thus forming a homogeneous particle containing the predetermined metal composition. Afterwards, the particles are annealed at a low temperature causing a phase separation of the metals, forming a metal nanoparticle that is surrounded by a stabilizing metal oxide. We have demonstrated that equimolar Fe, Ni, Co, Cr, and Mn solutions produce bifunctional FeNiCo metal nanoparticles surrounded by CrMnOx that are very active for both OER and ORR. The synthesis technique also affords the flexibility to tailor composition of the nanoparticles and potentially provide access to previously difficult to synthesize compositions and may alter the electrocatalytic reaction pathways and activities.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525

Al–Cu–Fe–Ni–Ti high entropy alloy nanoparticles as new catalyst for hydrogen sorption in MgH2

The earth's abundance of magnesium hydride (MgH2), along with its favorable qualities like high capacity, excellent reversibility, and cost-effectiveness under mild hydrogenation conditions, make it a potential material for hydrogen storage. Its practical applicability is limited by unfavorable thermodynamics and kinetics, despite these advantages. In this work, we investigate the use of a leached form of the mechanically alloyed high entropy alloy (HEA) Al–Cu–Fe–Ni–Ti as a catalyst to improve the hydrogen storage capabilities of MgH2. The onset desorption temperature of MgH2 is significantly reduced from 360 °C (for as-received MgH2) to 200 °C when catalyzed by the previously stated HEA catalyst. In addition, the catalyst exhibits enhanced kinetics, as it can absorb around 6.2 wt. % in just 2.3 min. at 300 °C and 15 atm of hydrogen pressure, and desorb approximately 5.8 wt. % in 3.8 min. When compared to other known catalysts, these results show some of the lowest desorption temperatures for MgH2. Furthermore, MgH2 catalyzed by the leached form of Al–Cu–Fe–Ni–Ti HEA exhibits good cyclic stability for up to 21 cycles, with just a small variation of about ∼0.02 wt. %. A thorough analysis using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy have been carried out. We suggest a workable catalytic mechanism for the high entropy alloy Al–Cu–Fe–Ni–Ti on MgH2 based on these findings.

Optimized Photothermal Conversion Ability through Interband Transitions in FeCoNiCrMn High-Entropy-Alloy Nanoparticles.

High-entropy-alloy nanoparticles (HEA-NPs) composed of 3d transition metallic elements have attracted intensive attention in photothermal conversion regions due to their d-d interband transitions (IBTs). However, the effect arising from the unbalanced elemental ratio still needs more focus. In this work, FeCoNiCrMn HEA-NPs with different elemental ratios among Cr and Mn have been employed to clarify the impact of different composed elements on the optical absorption and photothermal conversion performance. It can be recognized that the unbalanced elemental ratio of HEA-NPs can reduce the photothermal performance. Density functional theory calculation demonstrated that d-d IBTs can be changed by the different composed element ratios, resulting in a number of insufficient filling regions around the Fermi level (±4 eV). As a result, the HEA-NPs (FeCoNiCr0.75Mn0.25) with a balanced elemental ratio exhibit the highest surface temperature of 97.6 °C under 1 sun irradiation, and the evaporation rate and energy conversion efficiency could reach 2.13 kg·m-2·h-1 and 93%, respectively, demonstrating effective solar steam generation behavior.

Metal-organic framework-derived carbon-supported high-entropy alloy nanoparticles applied in ammonia borane hydrolytic dehydrogenation

While high-entropy alloy nanoparticle (HEA NP) catalysts from a sacrificial high-entropy-MOF (HE-MOF) have been attractive, their conventional characterizations may be misleading. Here, we report HEA NPs on HE-MOF-derived carbon (HE-MDC) via direct pyrolysis of MnFeCoNiCu HE-MOF in Ar and H2 at different temperatures and durations with a fast-ramping rate. With the profound investigations of the metal NPs on HE-MDCs by synchrotron radiation X-ray diffraction and absorption, we revealed that the Ar-treated HE-MDCs had either Cu-dominant solid solution or phase-segregated metal NPs, whereas H2 pyrolysis yielded well-dispersed HEA NPs on HE-MDCs. For ammonia borane hydrolysis, although the metal NP size in H2-treated HE-MDC was not the smallest, it showed the fastest dehydrogenation rate (TOF=5.76 molH₂∙min−1∙molcat-1), 2 ∼ 4 times faster than the Ar-treated HE-MDCs. It emphasized the crucial role of elemental uniformity in the HEA NPs over the traditionally reported catalyst size.

High entropy alloy nanoparticles decorated carbon-based electrode as interfacial Li-ion localized accelerators for anode-free lithium metal batteries

Lithium metal is deemed as the main representative of the material for next-generation energy storage cells. Nevertheless, the problems of lithium dendrite growth and anode electrode volume expansion have become difficult problems in practical applications. Here, we introduced lithophilic CuInNiSnCd HEA-NPs on the surface of three-dimensional (3D) carbon hosts through a high-temperature redox strategy (HEA/CF). The application of the HEA/CF 3D framework can effectively decrease the non-uniform current density of the anode electrode, thereby slowing down the volume expansion of lithium metal during cycling. The introduction of CuInNiSnCd HEA-NPs improves the lithophilic of the carbon substrate and reduces the nucleation potential of lithium. Meanwhile, their evolution process was monitored in situ by the dynamic electrochemical impedance spectroscopy (DEIS) with relaxation time (DRT) distribution analysis, and the introduction of the HEA was beneficial to improving Li+ migration kinetics. Consequently, the symmetric battery with Li@HEA/CF anode has an excellent cycle life of over 3000 h (10 mA cm−2/10 mAh cm−2). Furthermore, the anode-free HEA/CF assembled full cell has excellent rate performance with a stable CE of more than 99.2 % after 160 cycles at 1C. This research contributes to the use of high-entropy materials in advanced energy storage batteries and provides valuable guidance for enhancing the performance of lithium batteries.

Laser Precise Synthesis of Oxidation-Free High-Entropy Alloy Nanoparticle Libraries.

High-entropy alloy nanoparticles (HEA-NPs) show exceptional properties and great potential as a new generation of functional materials, yet a universal and facile synthetic strategy in air toward nonoxidized and precisely controlled composition remains a huge challenge. Here we provide a laser scribing method to prepare single-phase solid solution HEA-NPs libraries in air with tunable composition at the atomic level, taking advantage of the laser-induced metastable thermodynamics and substrate-assisted confinement effect. The three-dimensional porous graphene substrate functions as a microreactor during the fast heating/cooling process, which is conductive to the generation of the pure alloy phase by effectively blocking the binding of oxygen and metals, but is also beneficial for realizing accurate composition control via microstructure confinement-endowed favorable vapor pressure. Furthermore, by combining an active learning approach based on an adaptive design strategy, we discover an optimal composition of quinary HEA-NP catalysts with an ultralow overpotential for Li-CO2 batteries. This method provides a simple, fast, and universal in-air route toward the controllable synthesis of HEA-NPs, potentially integrated with machine learning to accelerate the research on HEAs.

Synthesis of AgCoCuFeNi High Entropy Alloy Nanoparticles by Hydrogen Reduction-Assisted Ultrasonic Spray Pyrolysis

Because of their high mixing entropies, multi-component alloys can exhibit enhanced catalytic activity compared to traditional catalysts in various chemical reactions, including hydrogenation, oxidation, and reduction processes. In this work, new AgCoCuFeNi high entropy alloy nanoparticles were synthesized by the hydrogen reduction-assisted ultrasonic spray pyrolysis method. The aim was to investigate the effects of processing parameters (reaction temperature, precursor solution concentration, and residence time) on the microstructure, composition, and crystallinity of the high entropy alloy nanoparticles. The characterization was performed with scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The syntheses performed at 600, 700, 800, and 900 °C, resulted in smaller and smoother spherical particles with a near-equiatomic elemental composition as the temperature increased to 900 °C. With 0.25, 0.1, and 0.05 M precursor solutions, narrower size distribution and uniform AgCoCuFeNi nanoparticles were produced by reducing the solution concentration to 0.05 M. A near-equiatomic elemental composition was only obtained at 0.25 and 0.05 M. Increasing the residence time from 5.3 to 23.8 s resulted in an unclear particle microstructure. None of the five metal elements were formed in the large tubular reactor. X-ray diffraction revealed that various crystal phase structures were obtained in the synthesized AgCoCuFeNi particles.

Thermal Stability of High-Entropy Alloy Nanoparticles Evaluated by In Situ TEM Observations.

High-entropy alloy (HEA) nanoparticles (NPs) have attracted attention in several fields because of their fascinating properties. The high mechanical strength, good thermal stability, and superior corrosion resistance of HEAs, which are derived from their high configurational entropy, are attractive features. Herein, we investigated the thermal stability of FeCoNiCuPd HEA NPs on reduced graphene oxide via in situ transmission electron microscopy observations at elevated temperatures. The HEA NPs maintained their structure, size, and composition at 700 °C, and their size gradually decreased accompanied by the preferential sublimation of Cu. On the contrary, the deterioration of the monometallic Pd NPs begins at temperatures greater than 700 °C according to Ostwald ripening, which involves the migration of adatoms or mobile molecular species. Theoretical calculations revealed that the detachment of adatoms from clusters (i.e., the first step of Ostwald ripening) was suppressed in the case of HEA NPs because of the high-configuration-entropy effect.

A Joule-heating-derived multiphase porous TiO2 support for reinforcing high-entropy alloy catalysts

Single-crystal nanocrystals of catalytic metals and oxides are essential for understanding chemical interactions on well-defined catalyst surfaces. However, a comprehensive understanding of the crystallographic origins for such enhancement has been lacking. This work provides formal evidence of the structure–property relationship through a model study on single-crystal TiO2. Our approach involves transient pulse heating to manipulate porosity and phase in epitaxially-grown TiO2 nanosheets along the (0 0 1) plane. Furthermore, we could introduce high-entropy alloy nanoparticles into the system, which exhibited excellent catalytic activity toward CO oxidation, achieving T90 at 143 °C. This improved performance is attributed to the interplay between the catalytic nanoparticles and the multiphase support, facilitating CO and O2 adsorption. Our study contributes to a fundamental understanding of structure–property relationships in heterogeneous catalyst systems. Overall, our thermal shock synthesis approach shows much promise for developing single crystal-based advanced nanocatalysts with broad practical implications.

Self-Encapsulation of High-Entropy Alloy Nanoparticles inside Carbonized Wood for Highly Durable Electrocatalysis.

High-entropy alloy nanoparticles (HEAs) show great potential in emerging electrocatalysis due to their combination and optimization of multiple elements. However, synthesized HEAs often exhibit a weak interface with the conductive substrate, hindering their applications in long-term catalysis and energy conversion. Herein, a highly active and durable electrocatalyst composed of quinary HEAs (PtNiCoFeCu) encapsulated inside the activated carbonized wood (ACW) is reported. The self-encapsulation of HEAs is achieved during Joule heating synthesis (2060 K, 2 s) where HEAs naturally nucleate at the defect sites. In the meantime, HEAs catalyze the deposition of mobile carbon atoms to form a protective few-layer carbon shell during the rapid quenching process, thus remarkably strengthening the interface stability between HEAs and ACW. As a result, the HEAs@ACW shows not only favorable activity with an overpotential of 7mV at 10mA cm-2 for hydrogen evolution but also negligible attenuation during a 500 h stability test, which is superior to most reported electrocatalysts. The design of self-encapsulated HEAs inside ACW provides a critical strategy to enhance both activity and stability, which is also applicable to many other energy conversion technologies.

Structural insights, synthesis, and electrocatalysis of high entropy nanoparticles for fuel cell, metal-air battery, and water-splitting applications

High-entropy alloy nanoparticles (HEA-NPs) have recently sparked great interest in materials science. Their solid-solution states, derived from distinct HEA configurations, make them promising candidates for catalysts with exceptional activity, stability, and tunable performance. However, a comprehensive understanding of the underlying mechanisms governing their electrocatalytic behavior is still lacking, hindering the rational design of HEA electrocatalysts. This review summarizes the fundamental knowledge of HEA-NPs, including the structure-activity correlations of HEA-NPs, diverse synthesis strategies, and applications in electrochemical catalysis. The design strategies for guiding improvements in tunable performance were highlighted. The article concludes with insights, perspectives, and future directions, encapsulating the state-of-the-art knowledge and paving the way for further exploration in this dynamic field.

Laser-thermal reduction synthesis of high-entropy alloys towards high-performance pH universal hydrogen evolution reaction

Owing to their multi-elemental compositions and unique high-entropy mixing states, high-entropy alloy (HEA) nanoparticles (NPs) displaying tunable activities and enhanced stabilities thus have become a rapidly growing area of research in recent years. However, the integration of multiple elements into HEA NPs at the nanoscale remains a formidable challenge, especially when it comes to the precise control of particle size, elemental composition and content. Herein, a simple and universal high-energy laser assisted reduction approach is presented, which achieves the preparation of HEA NPs with a wide range of multi-component, controllable particle sizes and constitution on different substrates within seconds. Laser on carbon nanofibers induced momentary high-temperature annealing (>2000 ​K and ramping/cooling rates > 105 ​K ​s−1) to successfully decorate HEA NPs up to twenty elements with excellent compatibility for large-scale synthesis (20.0 ​× ​20.0 ​cm2 of carbon cloth). The IrPdPtRhRu exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 16, 28, and 12 ​mV at a current density of 10 ​mA ​cm−2 in alkaline (1.0 ​M KOH), alkaline simulated seawater (1.0 ​M KOH ​+ ​0.5 ​M NaCl), and acidic (0.5 ​M ​H2SO4) electrolytes, respectively, and excellent stability (7 days and >2000 cycles) at the alkaline HER.