Cathodic Hydrogen Evolution Reaction Research Articles

Morphology-controlled nickel-organic framework nanosheet arrays for efficient urea electrolysis in alkaline media

Urea electrolysis is considered as a promising energy-saving hydrogen production technique to substitute the water electrolysis, but it is restricted by the lack of efficient and cost-effective catalysts. Herein, nickel foam supported three-dimensional (3D) nickel-organic framework nanosheet arrays (Ni-BDC-t/NF, where t is the reaction time) comprising Ni2+ and an organic ligand of 4,4-biphenyl dicarboxylic acid (BDC) are synthesized as catalyst for urea electrolysis in alkaline media. Benefiting from the highly exposed Ni active sites and fast electron transfer rate endowed by 3D nanosheet array architecture, the structurally optimized Ni-BDC-10/NF exhibits preeminent electrocatalytic activity and durability toward urea oxidation reaction (UOR). To deliver a high current density of 100 mA cm−2, the required UOR potential of Ni-BDC-10/NF is only 1.50 V vs. RHE. Significantly, by further coupling with the cathodic hydrogen evolution reaction, the urea electrolysis system based on Ni-BDC-10/NF self-supporting anode exhibits a dramatic voltage decrease by 340 mV at a current density of 50 mA cm−2 as compared with that of water electrolysis under the same conditions. This study provides some new ideas for developing high-efficiency nickel-based organic framework catalysts and their application in urea-related energy storage devices.

Small Molecule Oxidation Facilitated Seawater Splitting for Hydrogen Production: Opportunities and Challenges

Direct seawater splitting is an environment‐friendly and promising technology to replace freshwater electrolysis for hydrogen production. The challenge of seawater electrolysis lies in the competition between chloride oxidation reaction (CER) and oxygen evolution reaction (OER), as well as electrode corrosion and poisoning caused by chloride. Some small molecules have lower anodic electrocatalytic oxidation potentials compared to OER and CER, making them possible to substitute OER and/or CER in coupled electrolyzers not only to eliminate the electrode corrosion problem but also to significantly enhance the energy efficiency of seawater electrolysis. This article reviews the progress of such small molecule oxidation facilitated seawater electrolyzer. Starting with an overview of the key challenges in seawater electrolysis, this review introduces the fundamentals and advantages of the coupled seawater electrolyzers and discusses the strategies for anodic small molecule oxidation and cathodic hydrogen evolution reaction, including utilizing Cl‐ as a reactive medium, value‐added chemical synthesis, pollutants electrooxidation, and optimizing electrolyzers. Finally, the challenges and prospects of small molecule oxidation facilitated seawater splitting are summarized, aiming to provide impetus for research and development on coupled seawater electrolysis technologies.

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 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 orbital. The closer of orbital to the Fermi level showed the stronger the deprotonation ability. Meanwhile, in the high potential region, the broadening of 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 electronic 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.

Synergistic sulfur-doped tri-metal phosphide electrocatalyst for efficient hydrazine oxidation in water electrolysis: Toward high-performance hydrogen fuel generation

Replacing the slow anodic oxygen evolution reaction with the hydrazine (N2H4) oxidation reaction (HzOR) is a promising strategy for achieving energy-efficient hydrogen (H2) fuel production in water electrolyzer systems. Therefore, developing efficient electrocatalysts for the HzOR, in combination with the cathodic hydrogen evolution reaction, is essential for achieving high H2 fuel generation rates and advancing N2H4 fuel cell technology. In this study, we fabricated NiCoFe oxide derived from a metal-organic framework, followed by the physical mixing and carbonization of S and P. The strong intrinsic activity of S-doped tri-metal phosphide (TMP) against the HzOR is evidenced by its role in the chemisorption of N2H4 on its surface, where a dative link is formed between the electrons of the lone pair of nitrogen atoms in N2H4 and the empty orbitals of the metals in the TMP alloy. Using this process, we demonstrated the high performance of flow cell electrolysis for overall water and hydrazine oxidation by assembling the S-TMP||S-TMP electrode as both the anode and cathode of the electrolyzer. The resulting cell voltage was 0.35 V for HzOR and 1.53 V for overall water splitting, and the electric current density reached 10 mA·cm−2, with high stability over 20 h. The electrolyzer efficiency was significantly superior to that of electrolyzers constructed using other types of dual-purpose electrocatalysts as catalyst pairs. Furthermore, the overall effectiveness of the electrolyzer was comparable to that of electrolyzers incorporating two distinct, well-established, single-purpose electrocatalyst pairs for the water and hydrazine splitting reactions.

Grafting Ultra‐fine Nanoalloys with Amorphous Skin Enables Highly Active and Long‐lived Acidic Hydrogen Production

AbstractLarge‐scale deployment of proton exchange membranes water electrolysis (PEM‐WE) requires a substantial reduction in usage of platinum group metals (PGMs) as indispensable electrocatalyst for cathodic hydrogen evolution reaction (HER). Ultra‐fine PGMs nanocatalysts possess abundant catalytic sites at lower loading, but usually exhibit reduced stability in long‐term operations under corrosive acidic environments. Here we report grafting the ultra‐fine PtRu crystalline nanoalloys with PtxRuySez “amorphous skin” (c‐PtRu@a‐PtxRuySez) by in situ atomic layer selenation to simultaneously improve catalytic activity and stability. We found that the c‐PtRu@a‐PtxRuySez‐1 with ~0.6 nm thickness amorphous skin achieved an ultra‐high mass activity of 26.7 A mg−1Pt+Ru at −0.07 V as well as a state‐of‐the‐art durability maintained for at least 1000 h at −10 mA cm−2 and 550 h at −100 mA⋅cm−2 for acid HER. Experimental and theoretical investigations suggested that the amorphous skin not only improved the electrochemical accessibility of the catalyst surface and increasing the intrinsic activity of the catalytic sites, but also mitigated the dissolution/diffusion of the active species, thus resulting in improved catalytic activity and stability under acidic electrolyte. This work demonstrates a direction of designing ultra‐fine PGMs electrocatalysts both with high utilization and robust durability, offers an in situ “amorphous skin” engineering strategy.

Grafting Ultra-fine Nanoalloys with Amorphous Skin Enables Highly Active and Long-lived Acidic Hydrogen Production.

Large-scale deployment of proton exchange membranes water electrolysis (PEM-WE) requires a substantial reduction in usage of platinum group metals (PGMs) as indispensable electrocatalyst for cathodic hydrogen evolution reaction (HER). Ultra-fine PGMs nanocatalysts possess abundant catalytic sites at lower loading, but usually exhibit reduced stability in long-term operations under corrosive acidic environments. Here we report grafting the ultra-fine PtRu crystalline nanoalloys with PtxRuySez "amorphous skin" (c-PtRu@a-PtxRuySez) by in situ atomic layer selenation to simultaneously improve catalytic activity and stability. We found that the c-PtRu@a-PtxRuySez-1 with ~0.6 nm thickness amorphous skin achieved an ultra-high mass activity of 26.7 A mg-1 Pt+Ru at -0.07 V as well as a state-of-the-art durability maintained for at least 1000 h at -10 mA cm-2 and 550 h at -100 mA⋅cm-2 for acid HER. Experimental and theoretical investigations suggested that the amorphous skin not only improved the electrochemical accessibility of the catalyst surface and increasing the intrinsic activity of the catalytic sites, but also mitigated the dissolution/diffusion of the active species, thus resulting in improved catalytic activity and stability under acidic electrolyte. This work demonstrates a direction of designing ultra-fine PGMs electrocatalysts both with high utilization and robust durability, offers an in situ "amorphous skin" engineering strategy.

Thermodynamics of electrochemical urea oxidation reaction coupled with cathodic hydrogen evolution reaction in an alkaline solution: Effect of carbonate formation

The development of efficient and energy-saving electrochemical processes for "green" hydrogen generation represents one of the most crucial challenges in modern chemistry and technology. An effective approach to realizing such processes involves alkaline water electrolysis with cathodic hydrogen evolution coupled with anodic urea oxidation reaction. As extensively reported in the literature, this configuration allows for a significant reduction in cell voltage. In this work, we present thermodynamic analysis of the electrochemical reaction CO(NH2)2 + 2OH− ±6e– = 3H2 + N2 + CO32−, for the first time accounting for the inevitable carbonate formation due to interaction of carbon dioxide with alkali. Standard changes in enthalpy, entropy, and Gibbs free energy, as well as the electromotive force were calculated over the temperature range of 298–338 K. The influence of pH on the electromotive force value was investigated. It was observed that the process under study is accompanied by heat release and an increase in entropy, becoming thermodynamically spontaneous at pH > 12.66. From a thermodynamic point of view, this suggests exceptionally favorable energy characteristics for the studied process, promoting the development of an energy-efficient "green" hydrogen generation technology. Additionally, we demonstrate that increasing the temperature further enhances the thermodynamic features of this reaction by reducing the energy consumption for its progression.

Alleviating OH Blockage on the Catalyst Surface by the Puncture Effect of Single-Atom Sites to Boost Alkaline Water Electrolysis.

Nonprecious transition metal catalysts have emerged as the preferred choice for industrial alkaline water electrolysis due to their cost-effectiveness. However, their overstrong binding energy to adsorbed OH often results in the blockage of active sites, particularly in the cathodic hydrogen evolution reaction. Herein, we found that single-atom sites exhibit a puncture effect to effectively alleviate OH blockades, thereby significantly enhancing the alkaline hydrogen evolution reaction (HER) performance. Typically, after anchoring single Ru atoms onto tungsten carbides, the overpotential at 10 mA·cm-2 is reduced by more than 130 mV (159 vs 21 mV). Also, the mass activity is increased 16-fold over commercial Pt/C (MA100 = 17.3 A·mgRu-1 vs 1.1 A·mgPt-1, Pt/C). More importantly, such electrocatalyst-based alkaline anion-exchange membrane water electrolyzers can exhibit an ultralow potential (1.79 Vcell) and high stability at an industrial current density of 1.0 A·cm-2. Density functional theory (DFT) calculations reveal that the isolated Ru sites could weaken the surrounding local OH binding energy, thus puncturing OH blockage and constructing bifunctional interfaces between Ru atoms and the support to accelerate water dissociation. Our findings exhibit generality to other transition metal catalysts (such as Mo) and contribute to the advancement of industrial-scale alkaline water electrolysis.

Effect of Organic Corrosion Inhibitors on the Kinetics of the Cathodic Hydrogen Evolution Reaction on Steel in a Sulfuric Acid Solution

Effect of Organic Corrosion Inhibitors on the Kinetics of the Cathodic Hydrogen Evolution Reaction on Steel in a Sulfuric Acid Solution

Understanding of ammonium salts under-deposit corrosion: Electrochemical and AIMD investigations

In-situ electrochemical experiments and ab initio molecular dynamics (AIMD) simulations are combined to investigate the under-deposit corrosion and hygroscopicity of ammonium salts on SAE 1020 steel interdigital electrodes. The findings indicate that the hygroscopicity of ammonium salts influences the evolution of the interface and the accumulation of the product film. The corresponding simulations reveal that the hydrolysis of NH4+ leads to the generation of a proton transfer chain, resulting in an elevation of H+ concentration. This hydrolysis behavior is effectively catalyzed on the Fe(1 0 0) surface, promoting the occurrence of anodic adsorption and cathodic hydrogen evolution reaction, thereby inducing corrosion.

Metallic Nanoclusters for Electrochemical Water Splitting

AbstractElectrocatalytic water splitting is regarded as one of the most promising strategies for producing clean and sustainable energy sources (H2 and O2) in cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), respectively. Currently, transition metal nanoparticles (NPs) such as commercial Pt/C, IrO2, and RuO2 are still popular catalysts for industrial‐level HER and OER processes. However, both the high cost and low atomic utilization of NPs can not satisfy the requirements of atomic economy and green chemistry. Compared with NPs, metallic nanoclusters (NCs), which have higher atom utilization and optimized electronic structure than NPs, show unique activities for water splitting. In this review, the recently reported advanced design strategies for preparing various NCs are discussed in detail. The methods to control the particle size, coordinated environment, and morphology of NCs are also summarized. The electrochemical activity and stability of NCs can be influenced by the synergistic effect between NCs and supporting materials, which is also mentioned. Then, the recently reported state‐of‐art‐catalysts for both HER and OER along with the detailed catalytic mechanism are described to show the advanced design principles. Finally, the future perspectives and some remaining challenges are also presented.

First‐principle screening of corrosion resistant solutes (Al, Zn, Y, Ce, and Mn) in Mg alloys for Integrated Computational Materials Engineering guided stainless Mg design

AbstractMg alloy suffers from its poor corrosion resistance as a result of anodic dissolution of Mg and hydrogen evolution reaction (HER) in humid environments. In this study, the effects of alloying elements (Al, Zn, Y, Ce, and Mn) on both processes in Mg alloys have been quantitatively predicted. Using first‐principle calculations, we first obtained the substitution energies of alloying elements to compare their segregation preference, and then analyzed the influence of solutes at different layers on the stability and hydrogen adsorption properties of Mg(0001) surface by calculating the formation enthalpy, surface energy, vacancy formation energy, work function, Bader charge, deformation charge density, and adsorption free energy of H atom. It has been found that, on the one hand, the interior Mn solute atoms reduce the dissolution of Mg atoms and the transfer of electrons, consequently slowing down the anodic dissolution process. On another hand, the Mn, Y, and Ce elements on the surface inhibit the cathodic HER process by elevating the absolute value of hydrogen adsorption free energy, as a result of those solutes effectively controlling H adsorption behavior on Mg(0001) surface. In contrast, all five elements dissolved inside the Mg grain do not show significant effects on the H adsorption behavior.

Nickel‐Foam‐ and Carbon‐Nanotubes‐Fiber‐Supported Bismuth Oxide/Nickel Oxide Composite; Highly Active and Stable Bifunctional Electrocatalysts for Water Splitting in Neutral and Alkaline Media

To increase the effectiveness of both the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER), significant efforts are made to produce bifunctional water‐splitting electrocatalysts. In this study, bismuth oxide/nickel oxide (Bi2O3/NiO)‐based composite is supported over the nickel foam (Bi2O3/NiO‐NF) and carbon nanotube fiber (Bi2O3/NiO‐CNTF) to develop two different electrode systems for water‐splitting studies. For OER, Bi2O3/NiO‐NF and Bi2O3/NiO‐CNTF require overpotential of 401 and 369 mV, respectively, to achieve the current density of 50 mA cm−2 in alkaline media, while the current density of 50 mA cm−2 is achieved at overpotential of 398 and 304 mV, respectively, in neutral media. For HER, Bi2O3/NiO‐NF and Bi2O3/NiO‐CNTF achieve the current density of 50 mA cm−2 at overpotential of 301 and 268 mV, respectively, in neutral media. For overall water splitting in neutral media, Bi2O3/NiO‐CNTF achieves the current density of 50 mA cm−2 at cell voltage of 1.654 V. The promising performance of synthesized electrocatalysts reveals that the mixed metal oxides (p‐block and d‐block elements)‐based electrocatalysts can be potential candidates for practical water splitting in basic (1 M KOH) as well as neutral media (1 M phosphate‐buffered saline).

Recent Advances in Hydrogen Production from Hybrid Water Electrolysis through Alternative Oxidation Reactions

AbstractWater splitting driven by green electricity from renewable energy input to produce H2 has been widely considered as a promising strategy to realize the goals for future clean energy. However, in conventional overall water electrolysis, the sluggish kinetics and high onset potential of anode OER limit the cathode HER rate, which lowers the overall energy conversion efficiency. Over the past decade, an innovative concept involving hybrid water electrolysis by replacing OER with thermodynamically more favorable oxidation reactions coupling with the cathodic hydrogen evolution reaction has been devised to alleviate the limitations associated with the anodic OER. In this review, we summarize the recent progress concerning electrochemical hydrogen production by coupling the oxidation of molecules incorporating hydroxyl, aldehyde, and amino functional groups, with special emphasis on alternative reactions involving CO and sulfide. Finally, the remaining challenges and future perspectives are also discussed. We hope this review will accelerate the development of novel strategies for practicable H2 production from hybrid water electrolysis.

Climbing the Hydrogen Evolution Volcano with a NiTi Shape Memory Alloy.

Alkaline water electrolysis is a sustainable way to produce green hydrogen using renewable electricity. Even though the rates of the cathodic hydrogen evolution reaction (HER) are 2-3 orders of magnitude less under alkaline conditions than under acidic conditions, the possibility of using non-precious metal catalysts makes alkaline HER appealing. We identify a novel and facile route for substantially improving HER performance via the use of commercially available NiTi shape memory alloys, which upon heating undergo a phase transformation from the monoclinic martensite to the cubic austenite structure. While the room-temperature performance is modest, austenitic NiTi outperforms Pt (which is the state-of-the-art HER electrocatalyst) in terms of current density by ≤50% at 80 °C. Surface ensembles presented by the austenite phase are computed with density functional theory to bind hydrogen more weakly than either metallic Ni or Ti and to have binding energies ideally suited for HER.

An efficient cathode electrocatalyst for anion exchange membrane water electrolyzer

A high performance and durable electrocatalyst for the cathodic hydrogen evolution reaction (HER) in anion exchange membrane (AEM) water electrolyzers is crucial for the emerging hydrogen economy. Herein, we synthesized Pt–C core-shell nanoparticles (core: Pt nanoparticles, shell: N-containing carbon) were uniformly coated on hierarchical MoS2/GNF using pyrolysis of h-MoS2/GNF with a Pt-aniline complex. The synthesized Pt–C core-shell@h-MoS2/GNF (with 11.3 % Pt loading) showed HER activity with a lower overpotential of 30 mV at 10 mA cm−2 as compared to the benchmark catalyst 20 % Pt–C (41 mV at 10 mA cm−2) with improved durability over 94 h at 10 mA cm−2. Furthermore, we investigated the structural stability and hydrogen adsorption energy for Pt13 cluster, C90 molecule, h-MoS2 sheet, Pt13–C90 core-shell, and Pt13–C90 core-shell deposited h-MoS2 sheets using density functional theory (DFT) simulations. We investigated the Pt–C core-shell@h-MoS2/GNF catalyst active sites during HER performance using in-situ Raman analysis as well as DFT. We fabricated AEM water electrolyzers with cathode catalysts of Pt–C core-shell@h-MoS2/GNF and evaluated device performance with 0.1 and 1.0 M KOH at 20 and 60 °C. Our work provides a new pathway to design core-shell electrocatalysts for use in AEM water electrolyzers to generate hydrogen.

Bromine-mediated strategy endows efficient electrochemical oxidation of amine to nitrile.

Conventional methods for nitrile synthesis bring inherent environmental risks due to their reliance on oxidants and harsh reaction conditions. Meanwhile, direct electrooxidation of amines to nitriles suffers from low current density. In this study, we propose an innovative indirect electrooxidation strategy for nitrile formation, mediated by Br-/Br2, utilizing a highly efficient CoS2/CoS@Graphite Felt (GF) electrode. Notably, the anodic nitrile generation can be synergistically coupled with the cathodic hydrogen evolution reaction (HER). Through meticulous optimization of reaction parameters, we achieve an impressive 98% selectivity for octanenitrile at a current density of 60 mA cm-2 with a remarkable faradaic efficiency (FE) of 87%. Furthermore, our approach demonstrates excellent versatility, as we successfully evaluate both aliphatic and aromatic primary amines, highlighting its promising potential for practical applications in the field.

Advanced and Scalable Polyol-Mediated Synthesis Route for Highly Active Ni Metal Sulfides (M = Fe, Mn, Cr, Mo) As Efficient Electrocatalysts for Sea/Saline Water Oxidation

Recent studies have made significant progress in addressing oxygen evolution (OER), a bottleneck reaction in water electrolysis, by utilizing innovative electrode materials and catalysts to enable low-grade and saline water splitting, thus offering promising prospects for advancing sustainable hydrogen production systems.1 This study applied a modified polyol-mediated strategy2 to describe an advanced procedure for synthesizing NiMSx where M = (Fe, Mn, Cr, Mo). Several physical and chemical characterization tools are applied to investigate the obtained saline/seawater oxidation electrocatalysts, including XRD, SEM, TEM, and electrochemical characterization. The outcomes of these characterizations were displayed as graphs. The catalysts reveal nanoclusters morphologies. The figure below depicts the preliminary findings, illustrating the electrochemical performance and the physical characterizations. Figure 1 (a) and (b) represent the polarisation curves of the oxygen evolution activity of the synthesized MNiSx electrocatalysts on Carbon cloth and Ni foam working electrodes, respectively, in a three-electrode configuration with Pt wire serving as the counter and Hg/HgO serving as the reference electrode in 1M KOH plus natural seawater from the Galway Bay Ireland. The catalysts obtained a high current exchange density of above and close to the 200 mAcm-2. Figure 1(c) displays the images of the catalyst-coated working electrodes prepared via dip coating, both Ni foam and carbon cloth, while Figures 1(d) and 1(e) reveal the nanostructure-based clusters of the produced materials with the scanning and transmission electron microscopy, respectively. In addition, we are evaluating the efficacy of this high-performance anode electrocatalyst in a single cell with a working electrode area of 3 cm2 for the oxygen evolution reaction (OER) and Pt/C as a cathode for hydrogen evolution reaction (HER). Our research project aims to develop highly efficient Oxygen Evolution Reaction (OER) catalysts.We will employ various ex-situ and in-situ characterization techniques, including, Impedance spectroscopy, chronopotentiometry/chronoamperometry, Powder X-ray diffraction (XRD), Raman spectroscopy, and FTIR spectroscopy. Impedance spectroscopy determines the system's impedance as a function of frequency and offers insights into electrochemical behavior, such as resistance, capacitance, and charge transfer resistance. Chronopotentiometry/chronoamperometry will be applied to check the long-term stabilities of catalysts. X-ray diffraction (XRD) will examine the crystal structure of the stimuli in real-time during OER. X-ray photoelectron spectroscopy (XPS) will be applied to analyze the materials' surface chemistry and elemental composition by measuring the energies of emitted photoelectrons from X-ray irradiation. In-situ Raman spectroscopy will enable us to study changes in the catalysts' electronic structure and coordination environment during the reaction providing valuable insights into the underlying mechanism of OER. FTIR spectroscopy will reveal information about the response intermediates and mechanisms during OER. We can obtain a detailed understanding of the reaction pathway by monitoring the changes in the vibrational spectra of the reactants and products. Finally, post-mortem analysis of the catalysts will be performed after electrochemical testing to assess their degradation. Above all will help us optimize the catalysts' design for long-term stability and high-performance OER. Acknowledgments The authors acknowledge the ANEMEL Project funded by the Horizon Europe (European Innovation Council) Grant agreement 101071111. References Tong, W.; Forster, M.; Dionigi, F.; Dresp, S.; Sadeghi Erami, R.; Strasser, P.; Cowan, A. J.; Farràs, P., Electrolysis of low-grade and saline surface water. Nature Energy 2020, 5 (5), 367-377. Zhang, H.; Hyun, B.-R.; Wise, F. W.; Robinson, R. D., A generic method for rational scalable synthesis of monodisperse metal sulfide nanocrystals. Nano letters 2012, 12 (11), 5856-5860. Figure 1

(Keynote) Development of Advanced High Surface Area Metal Oxide Aerogels for Oxygen Evolution Reaction Electrocatalysis

The growing demand to shift energy production to sustainable sources poses some serious challenges. One of the biggest are the intermittent energy (wind and sun). To mitigate this issue, there is a critical need for large energy storage technologies, to store excess energy during the peak hours and carry it over for the rest of the day, weeks, and seasons. The best way to do so is through the Hydrogen Economy. At the heart of this scheme is green hydrogen production using water electrolysis.There are two distinct chemical reactions that take place in water electrolyzers: the cathodic hydrogen evolution reaction (HER), and the anodic oxygen evolution reaction (OER). Both reaction require catalysts to execute at high rates, and while the HER is considered to be relatively facile and takes place at low overpotentials, the OER requires relatively high overpotentials and high loadings of precious metal catalysts. It is considered the bottleneck reaction. The OER is a four electrons oxidation reaction per generated O2 molecule and proceeds in four distinct reaction steps. This leads to a very sluggish reaction kinetics and high overpotentials to reach viable current densities.In recent years, more and more non-precious metal OER catalyst have been developed. Most notably is the family of mixed nickel-iron oxyhydroxides (NiFeOOH), which are relatively cheap, selective and efficient catalysts in alkaline media, and their performance has been increased by optimizing the Ni:Fe ratio. One challenge that still remains is to increase the NiFeOOH surface area, and by that the electrochemically active site density (EASD).In this regard, one class of materials that has been attracting the attention of materials’ scientists in recent years are aerogels. Aerogels can be made from many different materials, such as silicates, carbons, metal organic materials, bio-inspired molecules, metals, and metal oxides. They consist of distinct units which form a porous 3D covalent framework (COF). Because of their diversity, aerogels have many different applications, e.g. as insulators, sensors, or catalysts.In this talk we will report the synthesis of NixFeyMzOOH aerogels, with a modified easy synthetic method via an epoxide route. These aerogels show much higher utilization of the material and overall increase in mass activity when catalyzing the OER when compared to other NiFeOOH derived materials. They were tested for their OER electrocatalytic activity and to the best of our knowledge these are the first aerogel materials that propagate OER themselves, rather than being used merely as support material for OER catalysts. The catalytic activity depends largely on the Ni:Fe ratio and not the surface area, which can lead to mass transport limitations when too high, showing an optimum for the ratio and the surface area.