Analysis of Trends and Emerging Technologies in Water Electrolysis Research Based on a Computational Method: A Comparison with Fuel Cell Research

Research and Development Investment and Collaboration Framework for the Hydrogen Economy in South Korea

South Korea developed its hydrogen strategies to achieve carbon neutrality and dominate the hydrogen economy amidst, and with the impetus, of the coronavirus disease 2019 (COVID-19) pandemic. The government strives toward the goal via continuous investment in green hydrogen technologies, as well as strategic collaborations. To facilitate the transition into the hydrogen economy, this study presents a research and development (R&D) investment and collaboration framework as a national strategy. The framework offers abundant information to elucidate the technology, R&D spectrum, and regional dimensions of the strategy. Furthermore, the proposed framework was applied to the Korean hydrogen economy comprising 955 nationally funded projects worth USD 565.7 million. The statuses and trends of the government’s investment in nationally funded research projects are illustrated with regard to the value chains of the hydrogen economies of 16 regions, as well as nine technology clusters relating to the hydrogen economy, thereby determining the research organizations that played crucial roles in each cluster of the 16 regions between 2015 and 2020. The results indicate that the research organizations in Daejeon acquired the highest government R&D funding in many hydrogen-economy-related research fields, and that an R&D spectrum-based research/strategic collaboration is required to accomplish specialized complexes in the regions.

High crystallinity design of Ir-based catalysts drives catalytic reversibility for water electrolysis and fuel cells

The voltage reversal of water electrolyzers and fuel cells induces a large positive potential on the hydrogen electrodes, followed by severe system degradation. Applying a reversible multifunctional electrocatalyst to the hydrogen electrode is a practical solution. Ir exhibits excellent catalytic activity for hydrogen evolution reactions (HER), and hydrogen oxidation reactions (HOR), yet irreversibly converts to amorphous IrO_x at potentials > 0.8 V/RHE, which is an excellent catalyst for oxygen evolution reactions (OER), yet a poor HER and HOR catalyst. Harnessing the multifunctional catalytic characteristics of Ir, here we design a unique Ir-based electrocatalyst with high crystallinity for OER, HER, and HOR. Under OER operation, the crystalline nanoparticle generates an atomically-thin IrO_x layer, which reversibly transforms into a metallic Ir at more cathodic potentials, restoring high activity for HER and HOR. Our analysis reveals that a metallic Ir subsurface under thin IrO_x layer can act as a catalytic substrate for the reduction of Ir ions, creating reversibility. Our work not only uncovers fundamental, uniquely reversible catalytic properties of nanoparticle catalysts, but also offers insights into nanocatalyst design.

Reversible multifunctionality in electrocatalysts can allow voltage reversal during device operation. Here, authors design a crystalline Ir-based electrocatalyst with a thin reversible metallic-Ir/IrO_x layer that shows activity for O₂ evolution, H₂ evolution, and H₂ oxidation.

Ar plasma-assisted P-doped Ni3S2 with S vacancies for efficient electrocatalytic water splitting

Doping engineering is considered an effective way to improve the electrocatalytic water splitting performance of catalysts. In this paper, P-doped Ni₃S₂/NF was prepared by Ar plasma-assisted chemical vapor deposition, where the P dopant was efficiently introduced into Ni₃S₂/NF under the assistance of Ar plasma. Meanwhile, numerous vacancies were generated due to plasma bombardment. In the doping process, the P dopants replace the S vacancies, which contributes to the strong bonding between the P dopants and Ni₃S₂. Due to the synergistic effect of the P dopants and S vacancies, the S_v-Ni₃S_2-xP_x-4 catalyst has low HER and OER overpotentials of 89 mV and 216 mV at 10 mA cm^-2, with a lower impedance value and good stability. The present work shows a facile route to introduce dopants and vacancies into catalyst materials for adding active sites, eventually improving their electrocatalytic performance.

An Optimized Balance of Plant for a Medium-Size PEM Electrolyzer: Design, Control and Physical Implementation

The progressive increase in hydrogen technologies’ role in transport, mobility, electrical microgrids, and even in residential applications, as well as in other sectors is expected. However, to achieve it, it is necessary to focus efforts on improving features of hydrogen-based systems, such as efficiency, start-up time, lifespan, and operating power range, among others. A key sector in the development of hydrogen technology is its production, renewable if possible, with the objective to obtain increasingly efficient, lightweight, and durable electrolyzers. For this, scientific works are currently being produced on stacks technology improvement (mainly based on two technologies: polymer electrolyte membrane (PEM) and alkaline) and on the balance of plant (BoP) or the industrial plant (its size depends on the power of the electrolyzer) that runs the stack for its best performance. PEM technology offers distinct advantages, apart from the high cost of its components, its durability that is not yet guaranteed and the availability in the MW range. Therefore, there is an open field of research for achievements in this technology. The two elements to improve are the stacks and BoP, also bearing in mind that improving BoP will positively affect the stack operation. This paper develops the design, implementation, and practical experimentation of a BoP for a medium-size PEM electrolyzer. It is based on the realization of the optimal design of the BoP, paying special attention to the subsystems that comprise it: the power supply subsystem, water management subsystem, hydrogen production subsystem, cooling subsystem, and control subsystem. Based on this, a control logic has been developed that guarantees efficient and safe operation. Experimental results validate the designed control logic in various operating cases, including warning and failure cases. Additionally, the experimental results show the correct operation in the different states of the plant, analyzing the evolution of the hydrogen flow pressure and temperature. The capacity of the developed PEM electrolysis plant is probed regarding its production rate, wide operating power range, reduced pressurization time, and high efficiency.

Sixteen Percent Solar-to-Hydrogen Efficiency Using a Power-Matched Alkaline Electrolyzer and a High Concentrated Solar Cell: Effect of Operating Parameters

The effect of electrode area, electrolyte concentration, temperature, and light intensity (up to 218 sun) on PV electrolysis of water is studied using a high concentrated triple-junction (3-J) photovoltaic cell (PV) connected directly to an alkaline membrane electrolyzer (EC). For a given current, the voltage requirement to run an electrolyzer increases with a decrease in electrode sizes (4.5, 2.0, 0.5, and 0.25 cm²) due to high current densities. The high current density operation leads to high Ohmic losses, most probably due to the concentration gradient and bubble formation. The EC operating parameters including the electrolyte concentration and temperature reduce the voltage requirement by improving the thermodynamics, kinetics, and transport properties of the overall electrolysis process. For a direct PV-EC coupling, the maximum power point of PV (P _max) is matched using EC I-V (current-voltage) curves measured for different electrode sizes. A shift in the EC I-V curves toward open-circuit voltage (V _oc) reduces the P _op (operating power) to hydrogen efficiencies due to the increased voltage losses above the equilibrium water-splitting potential. The solar-to-hydrogen (STH) efficiencies remained comparable (∼16%) for all electrode sizes when the operating current (I _op) was similar to the short-circuit current (I _sc) irrespective of the operating voltage (V _op), electrolyzer temperature, and electrolyte concentration.

Electric Load Influence on Performances of a Composite Plant for Hydrogen Production from RES and its Conversion in Electricity

The analysis here presented investigates the influence of electrical load on the operational performances of a plant for hydrogen production from solar energy and its conversion in electricity via a fuel cell. The plant is an actual one, currently under construction, in Reggio Calabria (Italy), at the site of the Mediterranean university campus; it is composed of a Renewable Energy Source (RES) section (photovoltaic panels), a hydrogen production section, and a fuel cell power section feeding the electrical energy demand of the load. Two different load configurations have been analysed and simulations have been carried out through HomerTM simulation code. Results allow interesting conclusions regarding the plant operation to be drawn. The study could have a remarkable role in supporting further research activities aimed at the assessment of the optimal configuration of this type of pioneering plants, designed for feeding electrical loads, possibly, in a self-sufficient way.

Powering the Hydrogen Economy from Waste Heat: A Review of Heat-to-Hydrogen Concepts

Ever-increasing energy demands and environmental concerns require new and clean energy supplies, many of which are intermittent and do not correlate with demand. To balance supply with demand, a universal energy vector should be employed such that intermittent renewable energy can be stored and transported and then used when needed. Hydrogen is the perfect universal energy vector and a possible solution that ensures environmental cleanliness, maximum utilization of renewable energy sources, and high efficiency, whereby the combustion of the fuel yields only water. One abundant and freely available energy source-both anthropogenic and natural-is heat. Heat can be obtained from industrial processes and is indeed often viewed as a waste product with a premium to remove but is notoriously difficult to capture, store, and transport. Capturing and storing low-grade heat therefore provides a significant opportunity and can be achieved by coupling thermoelectric generators and water electrolyzers. A thermoelectric generator is placed within a thermal energy gradient and produces a flow of current that is fed to the electrolysis unit with which it produces hydrogen and oxygen as the final products. The hydrogen can be stored for long periods and transported for "on-demand" use in fuel cells for electricity from hydrogen burners for a return to thermal energy. This Review summarizes the current state-of-the-art research into implementing thermoelectric generators and utilizing heat as a primary energy source to produce hydrogen, which could replace the need for extra electric power to run hydrogen production units. Furthermore, suitable requirements, modifications, and other related aspects associated with such a new and novel method of hydrogen generation are discussed. Hydrogen produced from otherwise-wasted energy sources can be considered to be green.

Recent Advances in Power-to-X Technology for the Production of Fuels and Chemicals

Environmental issues related to greenhouse gas emissions are progressively pushing the transition toward fossil-free energy scenario, in which renewable energies such as solar and wind power will unavoidably play a key role. However, for this transition to succeed, significant issues related to renewable energy storage have to be addressed. Power-to-X (PtX) technologies have gained increased attention since they actually convert renewable electricity to chemicals and fuels that can be more easily stored and transported. H2 production through water electrolysis is a promising approach since it leads to the production of a sustainable fuel that can be used directly in hydrogen fuel cells or to reduce carbon dioxide (CO2) in chemicals and fuels compatible with the existing infrastructure for production and transportation. CO2 electrochemical reduction is also an interesting approach, allowing the direct conversion of CO2 into value-added products using renewable electricity. In this review, attention will be given to technologies for sustainable H2 production, focusing on water electrolysis using renewable energy as well as on its remaining challenges for large scale production and integration with other technologies. Furthermore, recent advances on PtX technologies for the production of key chemicals (formic acid, formaldehyde, methanol and methane) and fuels (gasoline, diesel and jet fuel) will also be discussed with focus on two main pathways: CO2 hydrogenation and CO2 electrochemical reduction.

Multi-walled carbon nanotube and carbide-derived carbon supported metal phthalocyanines as cathode catalysts for microbial fuel cell applications

Metal phthalocyanine (CoPc and FePc) modified MWCNT or CDC materials were explored as superior cathode catalysts for MFC technology.

Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.

A New Class of Zn1 -x Fex -Oxyselenide and Zn1- x Fex -LDH Nanostructured Material with Remarkable Bifunctional Oxygen and Hydrogen Evolution Electrocatalytic Activities for Overall Water Splitting

The scalable and cost-effective H₂ fuel production via electrolysis demands an efficient earth-abundant oxygen and hydrogen evolution reaction (OER, and HER, respectively) catalysts. In this work, for the first time, the synthesis of a sheet-like Zn_{1- x} Fe_x -oxyselenide and Zn_{1- x} Fe_x -LDH on Ni-foam is reported. The hydrothermally synthesized Zn_{1- x} Fe_x -LDH/Ni-foam is successfully converted into Zn_{1- x} Fe_x -oxyselenide/Ni-foam through an ethylene glycol-assisted solvothermal method. The anionic regulation of electrocatalysts modulates the electronic properties, and thereby augments the electrocatalytic activities. The as-prepared Zn_{1- x} Fe_x -LDH/Ni-foam shows very low OER and HER overpotentials of 263 mV at a current density of 20 mA cm^-2 and 221 mV at 10 mA cm^-2 , respectively. Interestingly, this OER overpotential is decreased to 256 mV after selenization and the HER overpotential of Zn_{1- x} Fe_x -oxyselenide/Ni-foam is decreased from 238 to 202 mV at 10 mA cm^-2 after a stability test. Thus, the Zn_{1- x} Fe_x -oxyselenide/Ni-foam shows superior bifunctional catalytic activities and excellent durability at a very high current density of 50 mA cm^-2 . More importantly, when the Zn_{1- x} Fe_x -oxyselenide/Ni-foam is used as the anode and cathode in an electrolyzer for overall water splitting, Zn_{1- x} Fe_x -oxyselenide/Ni-foam(+)ǁZn_{1- x} Fe_x -oxyselenide/Ni-foam(-) shows an appealing potential of 1.62 V at 10 mA cm^-2 . The anionic doping/substitution methodology is new and serves as an effective strategy to develop highly efficient bifunctional electrocatalysts.