Efficiency Of Water Electrolysis Research Articles

Co-deposition of different mixed nanoparticle concentrations with nickel as efficient OER electrocatalysts in alkaline media

The catalytic efficiency of water electrolysis is directly affected by the oxygen evolution reaction (OER). DFT simulation was used to calculate the doping of SiC nanoparticles into Ni–Co alloys. The results indicate that doping nano SiC particles enhances the intrinsic activity of Ni–Co–SiC in OER by introducing a separate RDS at each of the four reaction sites. Then, magnetic field-induced jet electrodeposition was used to manufacture Ni–Co–SiC catalytic electrodes. To obtain a larger specific surface area of the micro/nano structure, nickel nanoparticles, and SiC nanoparticles were mixed in the form of mixed nanoparticles and then added to the electrolyte. The effect of mixed nanoparticle concentration on OER performance of Ni–Co–SiC catalytic electrodes was investigated. Research showed that the Ni–Co–SiC catalytic electrode exhibits micro/nano dense cellular protrusion structures with higher surface roughness with a magnetic field. OER performance of the Ni–Co–SiC catalytic electrode further increased with the concentration of nanoparticles, the catalytic electrode has excellent catalytic performance when the concentration of mixed nanoparticles reaches 6 g/L in the electrolyte. The overpotential of the Ni–Co–SiC/Ni catalytic electrode decreased to 309 mV, and the Tafel slope was 54.5 mV/dec.

Threshold current density for diffusion-controlled stability of electrolytic surface nanobubbles

Understanding the stability mechanism of surface micro/nanobubbles adhered to gas-evolving electrodes is essential for improving the efficiency of water electrolysis, which is known to be hindered by the bubble coverage on electrodes. Using molecular simulations, the diffusion-controlled evolution of single electrolytic nanobubbles on wettability-patterned nanoelectrodes is investigated. These nanoelectrodes feature hydrophobic islands as preferential nucleation sites and allow the growth of nanobubbles in the pinning mode. In these simulations, a threshold current density distinguishing stable nanobubbles from unstable nanobubbles is found. When the current density remains below the threshold value, nucleated nanobubbles grow to their equilibrium states, maintaining their nanoscopic size. However, for the current density above the threshold value, nanobubbles undergo unlimited growth and can eventually detach due to buoyancy. Increasing the pinning length of nanobubbles increases the degree of nanobubble instability. By connecting the current density with the local gas oversaturation, an extension of the stability theory for surface nanobubbles [Lohse and Zhang, Phys. Rev. E 91, 031003(R) (2015)] accurately predicts the nanobubble behavior found in molecular simulations, including equilibrium contact angles and the threshold current density. For larger systems that are not accessible to molecular simulations, continuum numerical simulations with the finite difference method combined with the immersed boundary method are performed, again demonstrating good agreement between numerics and theories.

Solar-Powered AEM Electrolyzer via PGM-Free (Oxy)hydroxide Anode with Solar to Hydrogen Conversion Efficiency of 12.44.

Water electrolyzers powered by renewable energy are emerging as clean and sustainable technology for producing hydrogen without carbon emissions. Specifically, anion exchange membrane (AEM) electrolyzers utilizing non-platinum group metal (non-PGM) catalysts have garnered attention as a cost-effective method for hydrogen production, especially when integrated with solar cells. Nonetheless, the progress of such integrated systems is hindered by inadequate water electrolysis efficiency, primarily caused by poor oxygen evolution reaction (OER) electrodes. To address this issue, a NiFeCo─OOH has developed as an OER electrocatalyst and successfully demonstrated its efficacy in an AEM electrolyzer, which is powered by renewable electricity and integrated with a silicon solar cell.

Fe–Ni-doped metal-organic framework derived CoSe2 as an efficient and stable electrocatalyst for hydrogen evolution reaction

The development of efficient, stable and low-cost catalysts for hydrogen evolution reaction (HER) is one of the major difficulties in water electrolysis. It is also the key to realizing the large-scale production of hydrogen energy, a renewable and clean energy source. In recent years, metal-organic frameworks (MOFs) have attracted much attention as novel precursors for preparing water electrolysis catalysts due to their high porosity and large specific surface area. In this paper, we use ZIF-67 as a precursor and modify it by doping transition metal elements Fe and Ni. Afterwards, Fe–Ni–CoSe2@NC is synthesized by a thermal selenization process. The results show that the HER overpotential of the catalyst after modification is reduced by 50%, and the efficiency of water electrolysis is significantly improved. Moreover, the catalyst has good stability under alkaline condition and is more economical than the expensive Pt-based catalysts, which provides more possibilities for industrial applications.

The electronic structure of the active center of Co3Se4 electrocatalyst was adjusted by Te doping for efficient oxygen evolution

In order to enhance the energy efficiency of water electrolysis, it is imperative to devise electrocatalysts for oxygen evolution reaction that are both non-precious metal-based and highly efficient. Efficient catalyst design is generally based on electronic structural engineering. Considering the electronegativity disparity between selenium (Se) and tellurium (Te), the tunable bandgaps, and the conductive metallic nature of Te. We designed a material wherein Te atoms are uniformly doped onto the surface of Cobalt tetra selenide (Co3Se4) nanorods, leading to the synthesis of a defect-rich material. Experimental results demonstrate that Te doping in Co3Se4 increases active sites and optimizes the electronic structure of Co cations, enhancing the design of multi-defect structures. This promotes the generation of the Co(oxy) hydroxide (CoOOH) active phase, enhancing catalytic activity by maximizing the binding strength between Co sites and oxygenated intermediates. Te-Co3Se4 nanorods exhibit good catalytic activity for oxygen evolution reactions, with an overpotential of 269 mV at a driving current density of 50 mA cm−2 and excellent stability in alkaline media (over 100 h). This discovery indicates the feasibility of strategically combining various imperfect structures, thereby unlocking the latent potential of diverse catalysts in electrocatalytic reactions.

Recent advances and perspective on transition metal heterogeneous catalysts for efficient electrochemical water splitting

AbstractThe development of advanced technology for producing high‐purity and low‐cost hydrogen is crucial for the upcoming hydrogen economy. One of the most promising technologies to achieve carbon peak and carbon neutrality is hydrogen production through water electrolysis coupled with renewable energy. However, the efficiency of water electrolysis is limited by the catalyst material employed, thereby the pursuit of highly efficient catalysts is of paramount scientific significance. In this review, we focus on the synthesis of electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) through various strategies such as hydrogen spillover, heterostructure construction, element doping, monatomic construction, LDH structure modification, high entropy alloy, and other approaches. The article also provides a comprehensive overview of the challenges encountered in enhancing the activity, stability, and durability of transition metal heterogeneous catalysts for both HER and OER. Moreover, the mechanisms of HER and OER are illustrated. The electrocatalysts prepared by these strategies have exhibited promising results in terms of water splitting performance. However, there are still unresolved issues that need to be addressed, such as improving long‐term stability and reducing overall cost. Future prospects include exploring new materials and optimizing the preparation methods to further enhance the electrocatalytic activity.

Investigation of the Hydrogen Gas Production by Using Solar Energy

Hydrogen is an energy source that offers both environmental benefits and reliability, making it a promising solution for promoting sustainable growth in various sectors worldwide. As businesses and societies increasingly seek sustainable alternatives, hydrogen has emerged as a key player in the transition to a low-carbon economy based on renewable energy sources. Consequently, hydrogen production holds immense potential for replacing traditional energy sources such as petroleum, natural gas, and non-renewable energy. Various methods can be employed for hydrogen production, including fossil fuel-based processes, nuclear energy, and renewable energy sources. To achieve the goal of zero emissions, the focus has shifted towards utilizing renewable energy, specifically through photovoltaic electrolysis, to generate hydrogen gas. Photovoltaic electrolysis employs solar energy to split water molecules into hydrogen and oxygen. However, the efficiency of this method is currently quite low. Temperature plays a crucial role in increasing the efficiency of water electrolysis, making it an important factor to consider in enhancing hydrogen gas production through photovoltaic electrolysis. Therefore, there is significant value in investigating the impact of temperature on the efficiency of hydrogen gas production in photovoltaic electrolysis. In summary, hydrogen energy production has emerged as a promising solution for sustainable growth, and renewable energy sources such as photovoltaic electrolysis hold great potential for achieving zero emissions. Exploring the influence of temperature on the efficiency of hydrogen gas production in photovoltaic electrolysis is of considerable interest, aiming to improve the overall process and enhance the viability of hydrogen as a sustainable energy source.

Graphene Architecture-Supported Porous Cobalt-Iron Fluoride Nanosheets for Promoting the Oxygen Evolution Reaction.

The design of efficient oxygen evolution reaction (OER) electrocatalysts is of great significance for improving the energy efficiency of water electrolysis for hydrogen production. In this work, low-temperature fluorination and the introduction of a conductive substrate strategy greatly improve the OER performance in alkaline solutions. Cobalt-iron fluoride nanosheets supported on reduced graphene architectures are constructed by a one-step solvothermal method and further low-temperature fluorination treatment. The conductive graphene architectures can increase the conductivity of catalysts, and the transition metal ions act as electron acceptors to reduce the Fermi level of graphene, resulting in a low OER overpotential. The surface of the catalyst becomes porous and rough after fluorination, which can expose more active sites and improve the OER performance. Finally, the catalyst exhibits excellent catalytic performance in 1 M KOH, and the overpotential is 245 mV with a Tafel slope of 90 mV dec-1, which is better than the commercially available IrO2 catalyst. The good stability of the catalyst is confirmed with a chronoamperometry (CA) test and the change in surface chemistry is elucidated by comparing the XPS before and after the CA test. This work provides a new strategy to construct transition metal fluoride-based materials for boosted OER catalysts.

Concerns on the Effects of Electrode Positions in Electrolyte Container for the Oxygen Evolution Reaction.

Water electrolysis is currently a major technique to produce clean hydrogen, which is regarded as a promising and sustainable energy carrier. The efficiency of water electrolysis is highly dependent on the oxygen evolution reaction (OER) on the anode. The evaluation of an OER electrocatalyst is frequently carried out on a three-electrode system in a container of electrolyte. Herein, we found that the electrode positions in the electrolyte container could significantly affect the data acquisition of OER performance. After a detailed investigation, we reveal that the difference of the OER activity of an electrocatalyst at a different position is originated from their different iRu drop and the gas diffusion resistance. For the first time, this work evokes concerns on the accurate evaluation of electrocatalysts regarding the electrode position. For fair comparisons and reliable results, it is strongly suggested to keep the electrode position unchanged in the electrochemical measurements. In addition, the establishment of a standard electrolyzer setup for electrocatalysis evaluation in the electrochemical community is also called for.

Effect of Electrode–Normal Magnetic Field on the Motion of Hydrogen Bubbles

In comparison to alternative methods for hydrogen production, water electrolysis stands out as the optimal means for obtaining ultra-pure hydrogen. However, its widespread adoption is significantly hampered by its low energy efficiency. It has been established that the introduction of an external magnetic field can mitigate energy consumption, consequently enhancing electrolysis efficiency. While much of the research has revealed that an electrode–parallel magnetic field plays a crucial role in enhancing the bubble detachment process, there has been limited exploration of the effect of electrode–normal magnetic fields. In this work, we compare the water electrolysis efficiency of a circular electrode subjected to electrode–normal magnetic field resulting in a magnet edge effect and electrode edge effect by varying the sizes of the magnet and electrode. The findings indicate that a rotational flow caused by the Lorentz force facilitates the detachment of the hydrogen from the electrode surface. However, the rotation direction of hydrogen gas bubbles generated by the magnet edge effect is opposite to that of electrode edge effect. Furthermore, the magnet edge effect has more significant influence on the hydrogen bubbles’ locomotion than the electrode edge effect. With an electrode gap of 30 mm, employing the magnet edge effect generated by a single magnet leads to an average of 4.9% increase in current density. On the other hand, the multiple magnet effects created by multiple small magnets under the electrode can further result in an average 6.6% increase in current density. Nevertheless, at an electrode spacing of 50 mm, neither the magnet edge effect nor the electrode edge effect demonstrates a notable enhancement in conductivity. In reality, the electrode edge effect even leads to a reduction in conductivity.

Proton Conduction over the Zeolite with Surface Water Cluster for the Water Electrolysis at Neutral Condition

AbstractElectrolytic hydrogen production from water at neutral pH was achieved by using novel proton (H+) conduction system assisted by zeolite. Experimental and computational insights demonstrated that defective silanol nest generated by dealumination played an important role in the formation of water clusters and the H+ conduction over the zeolites proceeded via exchange of H‐bonding between water molecules in the cluster. In addition, a proper balance between hydrophilicity and hydrophobicity is required for effective H+ conduction and silanol nest afford the balance. Furthermore, the contribution of hydrophilicity of the zeolite for the adsorption of water molecules became more drastic at high temperatures. Water electrolysis efficiency was strongly dependent on the H+ conductivity over the beta‐type zeolite. The electrolytic cell containing the zeolite has the potential to be applied to the new hydrogen production system.

First principles study on high-efficient overall water splitting by anchoring cobalt boride with transition metal atoms

Developing efficient, low-cost electrocatalysts is of great significance for improving the efficiency of water electrolysis. In this work, the structure, electronic properties, hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) activity of transition metal-doped cobalt boride (TM@CoB) were thoroughly investigated using density functional theory. Ni@CoB and Cu@CoB exhibited excellent catalytic activity for HER. Specifically, Ni@CoB demonstrated a ΔGH* value of 0.0537 eV, surpassing the most commonly used Pt catalyst. The reaction mechanism followed the Heyrovsky mechanism, and it also showed good OER activity, making it a potential candidate for OER electrocatalysts. Compared to the original CoB, Ni@CoB showed a 70 % improvement in HER activity and a 65 % improvement in OER activity. The Ni@CoB catalyst was synthesized, and its catalytic performance was experimentally validated. This work offers a new perspective and guidance for the development of bifunctional electrocatalysts.

Harnessing magnetic fields to accelerate oxygen evolution reaction

The challenge of overcoming the bottleneck in water electrolysis can potentially be addressed by utilizing permanent magnets without extra energy consumption, but the underlying mechanism of magnetic field effects is still puzzling despite increasing efforts in last few years. In this work, by dip-coating a superhydrophilic γ-Fe2O3 layer onto different electrode substrates, their surface wettability and magnetism are modified, so the ever-tangled effects of magnetic field are separated and identified. It is determined that the primary contribution of magnetic fields at the high current density was due to additional Lorentz force and Kelvin force exerted on oxygen gas bubble, with the former being dependent on the external magnetic field's geometry and the latter closely tied to the electrodes’ magnetism. Strategies to maximize effects of magnetic field as well as the overall efficiency of water electrolysis is proposed.

1D mesoporous NiFe2O4 nanorods fabricated by electrospinning for efficient oxygen evolution reaction

Designing and preparing efficient and stable oxygen evolution reaction (OER) catalysts is crucial to improve water splitting performance. One-dimensional (1D) structural catalysts have received increasing attention for the OER due to their unique structural characteristics. In this study, 1D mesoporous NiFe2O4 (NFO) spinel nanorods are fabricated by electrospinning, and the differences in physical structure and electrochemical performance of NFO nanorods prepared by different electrospinning precursors are investigated. It is found that the NFO nanorods prepared by precursor of nickel-iron hydroxide particles (denoted as NFOH) exhibit a diameter of approximately 200 nm and a surface area of 26.4 m2 g−1. In 1 M KOH solution, NFOH nanorods achieve low overpotentials of respective 316 mV and 396 mV to obtain current densities of 10 mA cm−2 and 50 mA cm−2, as well as a low Tafel slope of 67.2 mV dec−1, even lower than commercial NFO. Notably, the nanorods also demonstrate excellent long-term stability. The high OER activity can be attributed to the small nanoparticle size, abundant electrochemical active sites provided by the 1D mesoporous nanostructure, and increased conductivity, which promote charge/electron transfer and enhance the conversion of active species, thereby improving the efficiency of water electrolysis. This work may broaden the perspective and approach for the structural design of OER catalysts.

Towards a new perspective on the efficiency of water electrolysis with anion- conducting matrix

Achieving carbon neutrality in the future involves the use of low-carbon hydrogen as an energy source - in the power industry and heat supply of isolated areas - as a carbon-neutral fuel for generation and a secondary source of energy. In the transport sector, the prospects for the use of hydrogen extend to almost all types of vehicles - from cars, trains and ships to special-purpose equipment, air transport, both in fuel cells and in internal combustion engines.Rosatom State Corporation has developed a technology for producing hydrogen by water electrolysis using an anion-conducting matrix. The matrix is an inorganic fibrous material, and anionic conductivity is achieved as a result of the introduction of potassium cations during impregnation with a KOH solution. A wide range of productivity up to 115 % and the possibility of its dynamic change make it possible to effectively combine these electrolyzers with renewable energy sources.

HEA-NiFeCuCoCe/NF through ultra-fast electrochemical self-reconstruction with high catalytic activity and corrosion resistance for seawater electrolysis

The development of an electrocatalyst with excellent corrosion resistance and catalytic performance in seawater electrolysis is of great significance for advancing and utilizing sustainable hydrogen energy in the future. Additionally, the exploration of actual active sites to enhance the performance of OER (oxygen evolution reaction) is highly valuable in improving the overall efficiency of water electrolysis. To achieve these objectives, we synthesized a Ni-Fe-Cu-Co-Ce high entropy alloy (HEA-NCFCC) on a nickel foam (NF) substrate through electrodeposition. Subsequently, by employing an effective electrochemical self-reconstruction method, we successfully introduced M−OOH on the surface of the HEA-NCFCC/NF, resulting in a catalyst that exhibits both high OER activity and exceptional corrosion resistance (HEA-NCFCC/NF@EA). The catalyst's exceptional OER performance was clearly demonstrated by the experimental results, as evidenced by the achieved overpotentials of 219 mV, 220 mV, and 236 mV at current densities of 10 mA·cm−2 in alkaline solution, alkaline simulated seawater, and alkaline seawater, respectively. Furthermore, the HEA-NCFCC/NF@EA exhibited remarkable stability during continuous OER operation in alkaline simulated seawater and alkaline seawater, with a minimum operating time of 100 h. The outstanding corrosion resistance and catalytic performance of the HEA-NCFCC/NF@EA resulted from the distinctive synergistic effect intrinsic to the high entropy alloy itself and the incorporation of a stable lattice oxygen mechanism through electrochemical self-restructuring. This ensured that the catalyst remained highly resistant to significant erosion and reconstruction caused by chloride ions during continuous seawater electrolysis.

Unraveling the Fundamental Concepts of Superaerophobic/Superhydrophilic Electrocatalysts for Highly Efficient Water Electrolysis: Implications for Future Research

AbstractElectrochemical water splitting is a highly effective method for carbon‐free hydrogen production. While significant efforts have been made to develop efficient and cost‐effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the optimization of electrode surface properties has been largely overlooked. Inadequate mass diffusion, especially at high bath voltage, hampers the energy transfer efficiency of water electrolysis. To overcome these challenges, precise design of superaerophobic/superhydrophilic electrodes can effectively separate gas bubbles from the catalyst surface and enhance mass transfer, improving overpotential and Faraday efficiency. This article underscores the importance of designing electrocatalysts with well‐designed surface properties to address these challenges. It also discusses characterization techniques for evaluating surface properties and provides examples of applications for superaerophobic/superhydrophilic electrodes in energy storage and conversion systems, electrochemical biosensors, and industrial processes, etc. Overall, optimizing the surface properties of electrocatalysts holds promise for enhancing the efficiency of gas‐involving reactions and energy conversion systems.

Insight into pH-controlled bubble dynamics on a Pt electrode during electrochemical water splitting

Bubbles adhering to the electrode surface are the major factors causing the decreased efficiency of water electrolysis. In this work, the dynamic behaviors of oxygen bubbles on vertical platinum sheet electrodes were investigated by a high-speed camera and their corresponding current densities were measured simultaneously using an electrochemical workstation. The impact of wide range of electrolyte pH values (i.e., 1–13) on both the bubble nucleation number and the dynamics behaviors of bubbles was investigated under different applied voltages. When the applied voltage was increased from 1.6 to 1.7 V vs the saturated calomel electrode, the radius of bubbles upon detachment increased in acidic environments (pH = 1–7) and decreased in alkaline environments (pH = 7–13). In an alkaline environment, the Marangoni force plays an essential role here. Furthermore, the bubble detachment radius predicted by the force balance model is well matched with our experimental results. Our results demonstrate that bubble detachment is not favorable in a strongly acidic environment, whereas oxygen bubbles exhibit rapid detachment from the electrode surface in a strongly alkaline environment.

Enhanced hydrogen evolution performance of Co/CoP in electrolysis of water by interfacial regulation of crystal plane orientation

Modulating the heterojunction interface is an effective way to improve the electrocatalytic efficiency of water electrolysis, and the metal centers with preferred crystal plane orientation offer the potential to enhance the interfacial charge transfer and electrode reaction kinetics. In this study, a Co/CoP modified hydrogen evolution electrode with selective exposure of the metal-centered Co(002) crystal face was prepared using a one-step electrodeposition method by adjusting the P/Co molar ratio. Results demonstrate that the preferential orientation of Co(002) crystal face in Co/CoP leads to an increased electrochemical active surface area, significantly reduced interfacial impedance and Tafel slope. Moreover, it brings the d-band center closer to the Fermi level, which is thermodynamically favorable for hydrogen evolution reaction (HER). Under optimized conditions, Co/CoP exhibits overpotentials of 85 mV and 183 mV at 10 mA cm−2 and 100 mA cm−2, respectively. After long-term and cyclic stability tests, no significant activity decay is observed, demonstrating excellent hydrogen evolution activity and cyclic stability.

Integrating a Fischer Tropsch process into a pulp mill - A techno-economic assessment

To reduce the greenhouse gas emissions of the transport sector, synthetic fuels based on CO2 and H2 are one viable option. This paper evaluates the integration of a Fischer Tropsch process into a pulp mill to improve efficiency and to lower CO2 emissions. Different syngas preparation technologies, plant sizes, and gas loop designs are considered. The processes were simulated with a chemical process simulation software to retrieve mass and energy balances. Based on the simulations, the processes are evaluated regarding economics, CO2 emissions, and efficiency indicators.The Power-to-Fuel efficiency reaches almost 40 % for closed loop configuration with reverse water gas shift reactor for carbon monoxide production. For the open loop configuration the efficiency is tremendously lower. In closed loop configurations, the carbon efficiency reaches 80 %. The levelized cost of syncrude ranges from 3.28 to 7.69 €/kg. The most important impact on syncrude price comes from electricity price, investment cost, and efficiency of water electrolysis. Integrating the Fischer Tropsch process into the pulp mill shows advantages in terms of Power-to-Fuel efficiency and CO2 emissions but not necessarily in terms of economics.