Alkaline Water Research Articles

N-Doped Carbon-Incorporated Cobalt-Iron Mixed-Metal Phosphide Nanoboxes as Efficient Bifunctional Catalysts for Overall Water Splitting.

Optimizing the composition and structure of nanocatalysts is an efficient approach to achieving the top electrocatalytic performance. However, the construction of hollow nanocomposites composed of metal phosphides and highly conductive carbon to promote the electrocatalytic performance of metal phosphide-based catalysts is rarely reported. Herein, a CoFeP/C nanobox nanocomposite consisting of Co-Fe mixed-metal phosphides and N-doped carbon was successfully fabricated through an ion-exchange phosphidation strategy derived from ZIF-67 nanocubes. Benefiting from the synergistic effects between multiple components and the unique hollow structure, CoFeP/C nanoboxes can catalyze the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with high activity and stability. Furthermore, in the construction of an alkaline water electrolyzer using CoFeP/C nanoboxes as both OER and HER catalysts, they were capable of efficiently splitting water with a current density of 10 mA cm-2 achieved by applying only 1.62 V of cell voltage and exhibited outstanding durability. Density functional theory calculations demonstrate that synergistic effects among multiple components in CoFeP/C nanoboxes can lower the hydrogen adsorption free energy of the HER and OER energy barrier of the rate-determining step, thus promoting the catalytic reactions. The design and synthesis of CoFeP/C nanoboxes highlight the importance of the composition and structural characteristics in achieving high-performance water electrolysis.

Nanotechnology for sustainability of agriculture and environment: Green synthesis and application of nanoparticles – A review

Moreover, with the continuous population increase worldwide, there is more demand of food and other daily necessities, which require double agriculture production to provide adequate food for humanity from the same available natural resources. Therefore, looking for new techniques to combat various challenges is instantly needed to sustain crop production and provide enough food for humanity. The use of nano-technology in agriculture field represents an important tool for consistent production of agriculture crops and assists farmers with new practice management systems such as precision agriculture systems, the aim of which is to increase productivity and reduce expenses. Nanotechnology plays an important role in altering agriculture food production. The particles ranging from 1 to 100 nm are accounted as nanoparticles, which usually have high surface energy, big surface area and quantum quarantine. Most notably, nanoparticles increase crop yield by increasing the effectiveness of agricultural inputs to enable site-targeted, controlled nutrient delivery, assuring the least amounts of agro-inputs needed. Additionally, the main aim in agricultural production is to facilitate plants' faster adaptation to the increasingly severe climate change factors, such as high temperatures, low water availability, salinity, alkalinity and environmental pollution with heavy metals, without jeopardizing the delicate ecosystems that are currently in place. This review illustrates the effect of numerous nanoparticles on diverse plants of many concentrations, sizes and shapes. The molecular and genetic response to NPs, their method of action and their interactions with biomolecules should be the main areas of study in the future.

Electrode Selection and Catalyst Evaluation in Hydrogen Production from Alkaline Water Electrolysis: A Review

Generating hydrogen, through alkaline water electrolysis shows promise as an energy source. This review delves into the significance of choosing the electrodes and evaluating catalysts to enhance the efficiency and performance of hydrogen production. It summarizes the activation energy and losses linked to reactions in alkaline electrolysis emphasizing the necessity for electrode materials and catalysts. The review also touches upon challenges such as electricity consumption and platinum group metal based electro catalysts proposing various electrode materials and catalysts with superior activity and selectivity for hydrogen production. Additionally, it discusses electrolysis cell designs that facilitate separating by-products from hydrogen gas. The study reveals that with low over potentials of 70, 318, and 361 mV at 10, 500, and 1000 mA cm−2, respectively, NiOx/NF exhibits strong alkaline hydrogen evolution activity, resulting in great performance in alkaline HER. Moreover, it outlines advancements in alkaline water electrolysis technology focusing on enhanced efficiency and reduced operating costs associated with electricity consumption. Overall this review underscores the role of selecting electrodes and evaluating catalysts in optimizing hydrogen production from alkaline water electrolysis.

Holistic Dynamic Modeling and Simulation of Alkaline Water Electrolysis Systems Based on Heat Current Method

Hydrogen production technology is becoming increasingly important with the rapid development of hydrogen energy. Among existing hydrogen production technologies, alkaline water electrolysis (AWE) is drawing wide attention due to its advantages such as high maturity and low cost, and its performance analysis and optimization are important for applications. However, the AWE system contains processes with different physical and mathematical properties such as electrochemical reaction and heat transport processes, bringing difficulties to the system modeling. Moreover, the electrical and thermal processes have different characteristic time scales, and the system shows a sophisticated dynamic behavior, which has not been well studied yet. Here, a homomorphic dynamic model of the AWE system in the form of electrical circuit is built to describe the thermal and electrochemical processes uniformly, where the two parts are integrated via the energy conservation seamlessly. The model is verified by comparing with the experimental data and shows a high accuracy. The dynamic simulation analysis is conducted to investigate the dynamic response characteristics of the system under current step changes and fluctuations. The temperature overshoot and oscillation phenomena caused by delays in heat transport processes are studied. Results show that the time delay yields a maximum temperature overshoot of 10 °C, which would reduce the lifespan of the stack. This also highlights the importance of dynamic system analysis.

Distribution Characteristics and Formation Mechanism of Main Hydrochemical Ions in Qingshui River

Qingshui River is a vital source for human life and industrial production in Zhangjiakou City. Determination of the formation mechanism of the main hydrochemical ions is important for the sustainable development and utilization of surface water resources in the Qingshui River. In view of this, 20 surface water samples were collected from the agricultural and urban reaches of the Qingshui River in July 2022. Based on the detection of hydrochemical ions and stable isotopes （δ2H-H2O and δ18O-H2O）, the hydrogeochemical methods, multivariate statistical analysis, and positive matrix factorization model （PMF） were used to comprehensively understand the chemical formation mechanism of surface water from qualitative to quantitative perspectives. The results showed that the average pH value in the Qingshui River was 8.66, indicating weakly alkaline water. The average concentrations of cations and anions decreased in the orders of Ca2+ > Na+ > Mg2+ > K+ > NH4+ and HCO3- > SO42- > NO3- > Cl- > F- > NO2- in the river water, respectively. The main hydrochemical type was identified as HCO3-Ca·Mg water. For the natural background, surface water was mainly controlled by rock weathering and evaporation crystallization and rock weathering was identified as the primary driving factor. The main hydrochemical compositions in the Qingshui River were derived from the dissolution of carbonate rocks and silicate rocks. Regarding anthropogenic activities, the portions of river water in the agricultural reaches were mainly affected by the excessive application of chemical fertilizers. Furthermore, the concentration of NO3- （1.88-47.4 mg·L-1） exceeded the standard for drinking purposes （10 mg·L-1）. The concentration of F- （0.38-1.92 mg·L-1） was above the acceptable limit for drinking purposes （1.0 mg·L-1） in the southern urban reaches portion of the river water, which could have been attributed to the industrial sewage discharge. The obtained results from the PMF model showed that the hydrochemical compositions in the river water of agricultural reaches were mainly controlled by four factors, namely synthetic fertilizers （29.6%）, livestock manure （16.4%）, rock weathering （17.4%）, and natural geology （13.7%）, while hydrochemical compositions in the river water of urban reaches were mainly affected by the domestic pollutants （30.5%）, industrial discharges （20.1%）, natural geology （18.4%）, and rock weathering （16.7%）.

Thin Nickel Coatings on Stainless Steel for Enhanced Oxygen Evolution and Reduced Iron Leaching in Alkaline Water Electrolysis

ABSTRACTOne of the most mature technologies for green hydrogen production is alkaline water electrolysis. However, this process is kinetically limited by the sluggish oxygen evolution reaction (OER). Improving the OER kinetics requires electrocatalysts, which can offer superior catalytic activity and stability in alkaline environments. Stainless steel (SS) has been reported as a cost‐effective and promising OER electrode due to its ability to form active Ni‐Fe oxyhydroxides during OER. However, it is limited by a high Fe‐to‐Ni ratio, leading to severe Fe‐leaching in alkaline environments. This affects not only the electrode activity and stability but can also be detrimental to the electrolyzer system. Therefore, we investigate the effect of different Ni‐coatings on both pure Ni‐ and SS‐supports on the OER activity, while monitoring the extent of Fe‐leaching during continuous operation. We show that thin layers of Ni enable enhanced OER activities compared to thicker ones. Especially, a less than 1 µm thick Ni layer on an SS‐support shows superior OER activity and stability with respect to the bare supports. X‐ray photoelectron spectroscopy reveals traces of oxidized Fe species on the catalyst surface after OER, suggesting that Fe from the SS may be incorporated into the layer during operation, forming active Ni‐Fe oxyhydroxides with a very low Fe leaching rate. Utilizing inductively coupled plasma‐optical emission spectroscopy, we prove that thin Ni layers on SS decrease Fe leaching whereas the Fe from the uncoated SS‐support dissolves into the electrolyte during operation. Thus, OER active and stable electrodes can be obtained while maintaining a low Fe concentration in the electrolyte. This is particularly relevant for application in high‐performance electrolyzer systems.

Construction of δ-FeOOH/NiMn2S4 heterointerface for efficient alkaline oxygen evolution reaction

Alkaline water electrolysis driven by sustainable energy is a viable approach for large-scale green hydrogen production. The development of non-precious metal-based electrocatalysts that combine high activity and stability for the alkaline oxygen evolution reaction (OER) is of great importance. In this work, we design and construct a δ-FeOOH/NiMn2S4/NF heterointerface using a solvothermal/calcination process followed by a facile successive ionic layer adsorption reaction (SILAR) treatment. Experimental tests indicate that the formation of the heterogeneous interface between the δ-FeOOH and the NiMn2S4 creates a good electron transport channel for an efficient electrocatalytic process and improves the charge transfer kinetics. As a result, the prepared δ-FeOOH/NiMn2S4/NF exhibits a low overpotential of 210 mV at 10 mA cm−2 and a low Tafel slope value of 46.6 mV dec−1, and satisfactory stability with a 92.9 % retention after 72 h of OER operation at around 100 mA cm−2. In situ Raman and in-situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) tests show that the introduction of δ-FeOOH inhibits the oxidation of Ni2+ to Ni3+ and stabilizes the Ni-S bond to prevent its auto-oxidation, leads to an increase in the electrocatalytic OER activity.

Insights over the in-situ grown copper sulfide/NiFe-LDH composites for alkaline and urea water electrolysis

Harnessing hydrogen fuel through electrocatalytic water splitting offers an eco-friendly alternative to the traditional fossil fuels. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are the two half-cell reactions, that make up the electrocatalytic water splitting. Replacing the sluggish OER in the electrocatalytic water splitting with less energy demanding urea oxidation reaction (UOR) might benefit overall water splitting with reduced cell voltages. On the other hand, developing electrodes based on non-precious metals is essential for cost-effective and efficient water splitting. Herein, composites comprising non-precious nickel iron layered double hydroxide (NiFe-LDH) and copper (II) sulfide (CuS) are grown over the nickel foam and subjected to electrochemical measurements for alkaline water electrolysis (AWE) and urea water electrolysis (UWE). Structural and morphological investigations reveal that the 10 wt% CuS composited NiFe-LDH (NFCS10) is supposed to have effective catalytic features for water electrolysis. The electrochemical investigations in the three-electrode system with silver/silver chloride (Ag/AgCl, reference electrode) and platinum (Pt, counter electrode) revealed that the NFCS10 requires only a minimal overpotential (Ƞ50) of 235 mV for UOR and 400 mV for OER respectively. For bifunctional performance, NFCS10 requires an overall cell potential (OCP) of 1.65 V and 1.50 V to reach 10 mA/cm2 current density in AWE and UWE, respectively. X-ray photoelectron spectroscopy identifies the enrichment of oxygen vacancies in NiFe-LDH:CuS heterostructure, which could influence the charge transport and stability of the proposed electrode. This study emphasizes the interfacial interactions between the LDH and metallic sulfide, as well as their impact on the electrocatalytic activity in alkaline and urea water splitting.

Dynamic simulation of wind-powered alkaline water electrolysis system for hydrogen production

Alkaline water electrolysis (AWE) is a mature and cost-effective technology, especially suited for large-scale deployment, yet faces challenges in adapting to the dynamic nature of renewable energy sources. Evaluating AWE's adaptability to fluctuating renewable energy inputs is crucial. This study introduces a dynamic model to assess the influence of wind energy on a 250 kW industrial-scale AWE system for hydrogen production. This paper pioneers the utilization of Aspen Plus Dynamics for dynamic modeling, offering a comprehensive approach that incorporates all vital components and controllers of the balance of plant, such as gas-liquid separator, heat exchangers, deionized water supply, pumps, and the cooling loop. This methodology allows comprehensive simulation at the system level, revealing the real dynamic characteristics of the system under fluctuating wind energy conditions. Due to the absence of a dedicated module for AWE in Aspen Plus Dynamics, an integrated dynamic operation unit for the electrolyzer is constructed using Aspen Custom Modeler. The study analyzes the dynamic characteristics of the AWE system, specifically focusing on temperature, voltage, and liquid level. The study compares two temperature control strategies, before-stack and after-stack, with the refined after-stack method effectively addressing over-temperature issues and improving system energy efficiency by 1.44%.

Highly Efficient and Durable Water Electrolysis at High KOH Concentration Enabled by Cationic Group-Free Ion Solvating Membranes in Free-standing Gel Form.

The degradation of fixed cationic groups in most anion exchange membranes (AEMs) under alkaline environments limits their durability for alkaline water electrolysis (AWE). Ion-solvating membranes (ISMs) have emerged as a promising alternative to address this issue. Herein, a cationic group-free ion solvating membrane in a free-standing gel form (ISM-PBI-FG) is presented, created through a sol-to-gel transformation process followed by KOH imbibing. This approach yields a 3D porous microstructure composed of entangled polybenzimidazole (PBI) nanofibrils, achieving 89% porosity, which enables ultrahigh alkali uptake (346% in 6 M KOH) and exceptional ionic conductivity (763 mS cm-1 at 80 °C). The absence of cationic groups avoids the attack by OH-, thus ensures good alkaline stability with a conductivity retention rate of 91.6% over a 3120 h ex situ test in 6 M KOH. The resulting membrane delivered outstanding AWE performance with current densities of 5.5 A cm-2 using platinum-group-metal (PGM) catalysts and 2.2 A cm-2 using PGM-free catalysts at 2.0 V. Notably, the in situ electrolyzer device based on ISM-PBI-FG offers extensive operational flexibility ranging from 40-100 °C and demonstrates record durability in concentrated alkaline conditions, with a voltage decay rate of only 23.5µVh-1, outperforming most reported AEMs and ISMs.

Atmosphere-driven oriental regulation of Ru valence for boosting alkaline water electrolysis

Modulating the electronic characteristics of nanomaterials has been key to advancing sustainable energy technologies. In this study, we controlled the Ru electronic properties of NiRuOx by varying the calcination atmospheres (Air and Argon), resulting in two distinct electrocatalysts: NiRuOx-O2 with Ru4+ species and NiRuOx-Ar with Ru0 species as the main component. We established the relationship between the valence of Ru and its HER and OER catalytic activity as NiRuOx for example. Specifically, NiRuOx-Ar with metallic Ru demonstrates better alkaline HER activity with a smaller overpotential (94 mV) at 100 mA cm−2 than NiRuOx-O2 with Ru4+ due to the reduced Ru0 superiority towards H*. Conversely, NiRuOx-O2 shows superior alkaline OER performance with only 275 mV overpotential at 100 mA cm−2 compared with that of NiRuOx-Ar (383 mV) due to Ru4+ receiving electrons from Ni species and reduced Ru–O covalence. The NiRuOx-O2//NiRuOx-Ar electrolyzer in 1 M KOH achieves 10 mA cm−2 at 1.475 V with 100 h durability, surpassing the RuO2//Pt/C cell (1.516 V). Revealing the correlation between Ru valence and activity offers important insights for the rational design of Ru-based catalysts for HER and OER.

Numerical modeling of two-phase flow considering multiple bubble sizes in an alkaline water electrolyzer

Precise bubble flow description is crucial for predicting water electrolysis performance. This study employs the Euler-Euler model to simulate bubble flow in an alkaline water electrolysis cell, categorizing the dispersed gas bubble phase into three size classes: 30 ▪ (small), 90 ▪ (medium), and 270 ▪ (large). The volume fraction and velocity fields for each size class were simulated across three current densities, revealing distinct flow patterns: large bubbles exited directly through the outlet, while smaller bubbles were carried along by the circulating liquid. The simulated flow fields were compared with experimentally visualized flow fields, validating the model. Finally, the proposed model demonstrated its advantages over existing models, such as the monodispersed model and the population balance model (PBM), particularly in terms of upward flow velocity near the electrode and bubble descending height in the downward flow.

Effect of α-FeOOH in KOH Electrolytes on the Activity of NiO Electrodes in Alkaline Water Electrolysis for the Oxygen Evolution Reaction

Iron cation impurities reportedly enhance the oxygen evolution reaction (OER) activity of Ni-based catalysts, and the enhancement of OER activity by Fe cations has been extensively studied. Meanwhile, Fe salts, such as iron hydroxide and iron oxyhydroxide, in the electrolyte improve the OER performance, but the distinct roles of Fe cations and Fe salts have not been fully clarified or differentiated. In this study, NiO electrodes were synthesized, and their OER performance was evaluated in KOH electrolytes containing goethite (α-FeOOH). Unlike Fe cations, which enhance the performance via incorporation into the NiO structure, α-FeOOH boosts OER activity by adsorbing onto the electrode surface. Surface analysis revealed trace amounts of α-FeOOH on the NiO surface, indicating that physical contact alone enables α-FeOOH to adsorb onto NiO. Moreover, interactions between α-FeOOH and NiO were observed, suggesting their potential role in OER activity enhancement. These findings suggest that Fe salts in the electrolyte influence OER performance and should be considered in the development of OER electrodes.

3 nm-sized porous graphene-based anion exchange membranes for efficient and stable water electrolysis

Alkaline water electrolysis is one of the primary drivers of hydrogen energy development, and anion exchange membranes (AEMs) play a dual role in ensuring both conductivity and safety. However, traditional polymer AEMs have a wide pore size distribution and poor chemical stability, making it difficult to achieve a long-term balance between conductivity and safety of the water electrolysis system. Here, we select inorganic two-dimensional multilayer graphene oxide (GO) membranes as AEMs, using carboxylated wrinkled graphene (WG) and ethylenediamine (EDA) to create a cation-modified porous EDA-WG/GO (E-W/G) composite membrane with a 3 nm pore size. The enlarged channel size and enhanced hydrophilicity improve OH− permeability compared to the pristine GO membrane, while the strengthened hydration layer acts as a barrier to hydrophobic gases for O2/H2 separation. The results show that the prepared E-W/G membrane exhibits superior current density (600 mA cm−2) and gas impermeability (gas purity 99.99%) compared to the commercial Fumasep FAA-3-50 membrane (590 mA cm−2 and 99.81%, respectively). Furthermore, after continuous testing for 168 h in high-temperature and alkaline environments, the E-W/G membrane maintained conductivity comparable to its initial state and showed enhanced gas impermeability. Our strategy provides new insights into the design of high-performance AEMs and is expected to contribute to the advancement of the hydrogen energy industry.

FeCoNi-Based Alloy Coatings as Low Overpotential Electrocatalysts for Alkaline Water Electrolysis.

Developing efficient, stable and low-cost electrocatalysts is a viable approach to solve the current energy crisis. It is found that increasing the surface area of the electrodes can effectively promote the electrocatalytic efficiency. Herein, the atmospheric plasma spraying (APS) technology was used to prepare FeCoNi-Ni3C alloy coating by adding Ni3C powder to FeCoNi powder with an equal molar ratio. After mechanical mixing, the atomic ratios of Ni3C in the powder are 25 %, 50 %, and 75 %, respectively. The results prove that the pores on the surface of the coating have increased after Ni3C doping, which can provide more active sites in the electrocatalytic process to promote the electrocatalytic reaction. By controlling the proportion of Ni3C, the porosity of the coating surface can be effectively regulated. The results suggested that in 1.0 M KOH electrolyte and 10 mA cm-2, the FeCoNi coating shows an overpotential of 191 and 277 mV for HER and OER, respectively, the HER overpotential of 50 at % Ni3C FeCoNi-Ni3C coating is 105 mV, and the OER overpotential is 212 mV. It is worth noting that the 50 at % Ni3C FeCoNi-Ni3C coating has a low Tafel slope of 45.78 mV dec-1 (HER) and 44 mV dec-1 (OER). Meanwhile, the attenuation of the overpotential of the 50 at % Ni3C FeCoNi-Ni3C coating after the stability test is almost negligible, indicating that the prepared catalyst has excellent electrocatalytic stability. Furthermore, the 50 at.% Ni3C FeCoNi-Ni3C coating catalyst has a low potential of 1.664 V at 10 mA cm-2 in a water-splitting system. This work provids a new idea for designing inexpensive electrocatalysts.

Electrodes: Flat vs Pin-Type Topology in Alkaline Water Electrolysis

The energy transition is already underway, and hydrogen plays a crucial role by enabling renewable energy storage without emitting carbon dioxide and other greenhouse gases. Given the intermittency of renewable energy sources, energy storage is essential in this transition. Hydrogen technologies are recognized as promising solutions. One method to produce green hydrogen is through water electrolysis using renewable energy sources, a process identified with significant potential for decarbonization. However, it needs to enhance efficiency, reduce component costs, and consequently, production costs to expand its adoption. Alkaline water electrolysis for hydrogen production is a mature technology with commercially available megawatt (MW) scale installations. To enhance the performance of alkaline electrolyzers, this study focuses on evaluating flat and pin-type electrodes. To analyze their performance, the electrodes were tested at, 20 degrees Celsius, varying electrode distances between them. Tests were conducted in an electrochemical cell, where different operating voltages were applied incrementally, from 0.1 [V] every 30 seconds, across a range of 0 to 2.7 [V]. From the analyzed distances, the highest current densities were obtained at 1.95 [mm] for the pin type and 4.59 [mm] for the flat. Comparing performances at comparable distances, it is observed that the flat electrode generates a higher current density than the pin type. Although the pin-type electrode increases its surface area by approximately 83%, it hinders the detachment of bubbles, causing them to remain on the electrode’s surface for a longer time and reducing its performance.

Influence of Physico-Chemical Parameters on the Seasonal Dynamic of <i>Salmonella </i>spp Isolated from Urban Streams in Yaounde (Cameroon)

As water resources in urban areas are becoming increasingly degraded, due in large part to poor sanitation, a study has been was conducted to examine the influence of physicochemical parameters and seasonal variation on the distribution of the enterobacteria <i>Escherichia coli</i> and <i>Salmonella </i>spp that have been isolated from the urban streams in the city of Yaounde. Bi-monthly water samples were collected from nine rivers during 12 months (April 2010 to March 2011). The isolation of bacterial germs was done according to the classical method. Physicochemical parameters were analyzed according to Standard methods. <i>Salmonella </i>spp was detected all over the studied year with a high prevalence of 49.4%. This prevalence varies from one season to another. <i>Escherichia coli</i> ranged between 2.5 x 10<sup>3</sup> to 67.1 x 10<sup>3</sup>UFC/100ml with highest prevalence observed during the long dry season. Physicochemical parameters revealed neutral to slightly alkaline waters (pH6.7 – 8.8), with low mineralization (EC= 126 – 743 µS/cm). Dissolved oxygen was generally less than 4 mg/l. Physicochemical parameters also showed temporal homogeneity in most of the variables (pH, EC, TDS, total hardness, alkalinity, Na, K, Mg, Ca). None of the physicochemical environmental variables analyzed had any specific influence on the presence of <i>Escherichia coli</i> or <i>Salmonella</i>. Furthermore, there was no significant correlation between the presence of <i>Escherichia coli</i> and <i>Salmonella </i>spp, as the sources of <i>Salmonella</i> spp contamination are probably different from those of <i>E. coli</i>. The observed pollution of rivers is related to the large anthropogenic activities in particular, the multiplicity of small farming closed to markets and houses, and husbandry activities along the streams which are important sources of organic matter. These rivers constitute a pool of <i>Salmonella</i> that can be easily disseminated in to different ecological systems and therefore represent a serious health risk for people who may come into direct or indirect contact with this pathogen.

Fe dimers incorporated within Ni(OH)2 nanosheets to enable rapid oxygen radical coupling and exceptional durability in oxygen evolution

Earth-abundant NiFe (oxy)hydroxides are promising substitutes for scarce noble-metal electrocatalysts in the oxygen evolution reaction (OER), yet their commercialization in alkaline water electrolyzers is hindered by poor durability. Here, we report that different Fe configurations can be deliberately incorporated into Ni(OH)2 nanosheets in FezNi1-zOxHy (z=0–0.4) via in-situ electrochemical delamination. The strongly synergistic catalysis between Fe dimers and low-valence host Ni(2-δ)+ is enhanced by the interactively roaming space-charge, which dynamically adapts to varying intermediates, mediating the oxide path mechanism, thereby accelerating deprotonation and oxygen radical coupling. Beyond high catalytic activity, the extended Ni-O shells surrounding Fe dimers create a locally flexible reaction microenvironment that prevents Fe dissolution at dynamic catalyst/electrolyte interfaces, ensuring ultralong-term stability at industrial OER current densities. This study highlights the great potential for commercial alkaline freshwater and seawater electrolysis, and offers new strategies for atomically manipulating metal species in (oxy)hydroxides to develop active and durable electrocatalysts.

Synergistic Configuration of Binary Rhodium Single Atoms in Carbon Nanofibers for High-Performance Alkaline Water Electrolyzer.

Electrochemical alkaline water electrolysis offers significant economic advantages; however, these benefits are hindered by the high kinetic energy barrier of the water dissociation step and the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline media. Herein, the ensemble effect of binary types of Rh single atoms (Rh-Nx and Rh-Ox) on TiO2-embedded carbon nanofiber (Rh-TiO2/CNF) is reported, which servesas potent active sites for high-performance HER in anion exchange membrane water electrolyzer (AEMWE). Density functional theory (DFT) analyses support the experimental observations, highlighting the critical role of binary types of Rh single atoms facilitated by the TiO2 sites. The Rh-TiO2/CNF demonstrates an impressive areal current density of 1 A cm-2, maintaining extended durability for up to 225 hin a single-cell setup. Furthermore, a 2-cell AEMWE stack utilizing Rh-TiO2/CNF is tested under industrial-scale conditions. This research makes a significant contribution to the commercialization of next-generation high-performance and durable AEMWE stacks for clean hydrogen production.

Benchmarking performance: A round-robin testing for liquid alkaline electrolysis

Liquid alkaline water electrolysis has gained considerable interest in recent years due to its promising role in an energy sector based on renewable energy sources. Its main advantage is the low investment cost of industrial alkaline water electrolyzers compared to other electrolysis technologies. A challenge remains in developing cost-efficient materials, stable in corrosive electrolytes, and offering competitive cell performance. Although there are many publications in liquid alkaline electrolysis, there is insufficient standardization of experimental conditions and procedures, reference materials, and hardware. As a result, comparability and reproducibility suffer, significantly slowing down research progress. This manuscript presents the initial efforts towards the development of such reference hardware and procedures within the framework of Task 30 Electrolysis in the Technology Collaboration Programme on Advanced Fuel Cells (AFC TCP) of the International Energy Agency (IEA). For this purpose, a homogenized setup including the electrolysis cell, functional materials, experimental conditions, and a test protocol was developed. The protocol and hardware were tested simultaneously at eleven different institutions in Europe and North America. To evaluate the success of this approach, polarization and run-in data were collected and analyzed for comparison, and performance differences were calculated. Significant disparities between the laboratories were observed and some key influence factors were identified: iron content in the electrolyte resulted to be a main source of deviation between experiments, along with temperature control and the conditioning of the cells. The results suggest that additional attention to detailed experimental conditions should be paid to obtain meaningful performance data in future research.