Recent Advances and Future Prospects on Industrial Catalysts for Green Hydrogen Production in Alkaline Media

Abstract

Green hydrogen is obtained by electrochemical water splitting using electricity converted from renewable energy sources. When green hydrogen undergoes combustion, it produces only water, leading to zero CO2 emissions from the source, which is important for the global energy transition. The sluggish kinetics of the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) in alkaline media have hindered an enhancement in hydrogen production from electrochemical water splitting. A detailed understanding of the alkaline reaction kinetics is important to accomplish the global mission of carbon neutrality. This review presents the theoretical kinetics for the HER and OER in alkaline media using different designed electrocatalysts, and discusses their corresponding reaction mechanisms. Subsequently, current design concepts and generalities on catalysts for water electrolysis are discussed. Enhancements in the OER activity for alkaline water electrolysis can be achieved through strategies that are classified into two major categories. In the first category, the exposure of numerous active sites is achieved by engineering the morphology and obtaining a high surface area. In the second category, the intrinsic activity of the catalyst toward the OER is enhanced by heteroatomic participation, vacancy formation, and the use of heterogeneous media. Advanced characterization techniques and in-situ testing techniques have confirmed the presence of complex oxidation media for the OER, which have a significant impact on the catalyst structure and local coordination. Research on the active sites of the catalyst, high concentrations of active species, and the design of highly efficient reaction media is required to further drive catalyst development for the OER. The evaluation of electrocatalysts exhibiting high performance at high current densities to produce green hydrogen is crucial for their implementation in industrial applications. Currently, large-scale synthesis a key technology to obtain industrial electrodes. Meanwhile, the construction of superaerophobic electrodes and threedimensional electrodes facilitates the design of high-performance industrial catalytic electrodes. Subsequently, three different electrolytic cells that are typically used to obtain green hydrogen at the industrial scale are presented. The limitations to the design of electrolytic cells and the related solutions are also discussed. In-depth investigations on the design of either industrial electrocatalysts, commercial membranes, or electrolyzers can improve the understanding of industrial design principles to be applied to obtain industrial electrolyzers with increased efficiency, safety, and practicality. Finally, recent developments on electrocatalysts for water splitting and their limitations for industrial applications are presented to provide new perspectives and guidelines on the preparation of next-generation electrolytic catalysts.

Study on Water Splitting of the 214-Type Perovskite Oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga)

“…The rate-determining steps for these three catalysts include all of the generation of O 2 from the OOH*, and the calculated Gibbs free energy changes (Δ G ) are 4.10, 2.68, and 3.37 eV, respectively. PrSrCoO 4 exhibits the lower Δ G and the larger DOS, reducing the energy barrier of the OER reaction process and improving the electrocatalytic performance. − …”

Tin as a co-catalyst for electrocatalytic oxidation and reduction reactions

“…For example, as an ultimate solution for providing energy resources, green hydrogen, produced through the HER during water electrolysis, provides hope for the future, applicable not only in fuel cells but also in various industries. [6][7][8][9][10][11] On the other hand, the ORR plays a critical role as the rate-determining reaction in various fuel cells such as proton exchange membrane fuel cells (PEMFCs) and zinc-air batteries. [12][13][14][15][16][17][18] Toward the electrochemical oxidation of biomass-derived alcohols, including ethanol, the utilization of the EOR in direct ethanol fuel cells (DEFCs) offers an effective means of harnessing the chemical energy of ethanol to produce clean electricity, particularly for mobile and portable devices.…”

Nanoporous Nickel Cathode with an Electrostatic Chlorine-Resistant Surface for Industrial Seawater Electrolysis Hydrogen Production

“…Alkaline seawater electrolysis based on offshore renewable energy electricity has emerged as a sustainable and economically viable technology for green hydrogen production. − Electrodes are at the heart of the electrolytic system and play a pivotal role in determining the energy efficiency of such a electricity–hydrogen conversion process. − Metallic Ni mesh/foam serves as the cathode material in a commercially mature alkaline water electrolysis system. − However, the Ni mesh/foam materials suffer from significant deficiencies in a seawater electrolysis environment: (I) chloride-ion-associated Ni metal corrosion, resulting in the poor structural and electrochemical stability of Ni mesh/foam electrodes; − (II) limited electrode surface area and (III) low intrinsic activity of metallic Ni sites, both of which lead to limited electrocatalytic activity and high working overpotentials. − To date, developing a Ni-based cathode with high electrocatalytic activity and stability for industrial seawater electrolysis remains a tough challenge.…”