J. P. Pramod, B. Nagarjuna Reddy, B. Prasanna Lakshmi, P. R. Sekhar Reddy
The oxygen evolution reaction (OER) plays a critical role in electrochemical water splitting and renewable energy conversion systems. However, the sluggish reaction kinetics and high overpotential of OER remain major challenges for efficient hydrogen production. Recently, cobalt oxide (Co 3 O 4) nanomaterials have attracted significant attention as promising electrocatalysts due to their low cost, high catalytic activity, environmental compatibility, and rich redox chemistry. Various nanostructured morphologies including nanoparticles, nanosheets, nanowires, hollow structures, and porous architectures have demonstrated improved electrocatalytic performance by increasing active surface area and facilitating rapid charge transfer. Furthermore, composite formation with conductive carbon materials and heteroatom doping strategies have significantly enhanced the electrical conductivity and stability of Co 3 O 4 -based catalysts. This mini review summarizes recent advances in Co 3 O 4 nanomaterials for oxygen evolution reactions, focusing on synthesis methods, nanostructure engineering, electrical properties, and electrochemical performance. In addition, current challenges and future perspectives for developing highly efficient and durable Co 3 O 4 electrocatalysts are discussed.
Sakshi Bhardwaj, Greesh Kumar, Tahir Naveed Jahangir, Raju Kumar Gupta, Takaya Ogawa, Manisha Das, Laurent Billon, Sabuj Kanti Das
Developing economical and highly active metal-free electrocatalysts for the hydrogen evolution reaction (HER) is crucial for advancing sustainable hydrogen energy through water electrolysis. Although alkaline water electrolysis holds great potential as a scalable technology, the process is hindered by two major challenges: the sluggish water dissociation step and the limited intrinsic activity of metal-free catalysts. Here, we report TFPheMePh, a nitrogen-containing, hydroxyl-functionalized covalent organic framework (COF) synthesized via polycondensation, yielding a crystalline, porous material with a high BET surface area of 1309 m 2 g -1. To maximise catalyst utilisation and facilitate efficient electron transport, the synthesized COF was drop-casted onto a three-dimensional dynamic hydrogen bubble template copper foam (DHBT-Cuf). Its interconnected porous architecture provides a highly conductive scaffold, enhanced electrolyte accessibility, and abundant exposed active sites, thereby facilitating water activation and HER. The resulting COF/DHBT-Cuf electrode delivers efficient HER activity in 1 M KOH, achieving an overpotential of 285 mV at 10 mA cm -2 with a Tafel slope of 263 mV dec −1. This performance arises from the synergy of nitrogen-rich active sites, phenolic groups, the electron-donating inductive effect of methyl substituents, a high-surface-area microporous channel network, and an extended π-conjugated backbone, collectively promoting charge transport, reactant accessibility, and catalytic kinetics. This work highlights the potential of the rational design of COFs integrated with three-dimensional conductive architectures as efficient metal-free electrocatalysts for alkaline HER and provides valuable insights into the development of advanced organic framework-based catalysts for sustainable green hydrogen production.
Akeem Adeyemi Oladipo, Aliyu Ahmed Ibrahim, Abimbola O. Aleshinloye, Adewale Sulaiman Oladipo
The dual imperatives of carbon-neutral chemical manufacturing and advanced wastewater remediation require high-performance electrocatalysts capable of orchestrating complex, multi-electron reactions. However, pristine catalyst lattices are fundamentally bottlenecked by linear scaling relations. This critical review establishes defect engineering as the definitive strategy for bypassing these thermodynamic limitations, offering a unified mechanistic framework that bridges sustainable energy conversion and environmental remediation. Moving beyond empirical material catalogues, this work systematically interrogates how localized structural imperfections—vacancies, dopants, and synergistic interfaces—act as precision atomic-scale electronic regulators. By modulating the transition-metal d-band center and triggering spatial charge redistribution, defects successfully decouple intermediate binding energies to steer reaction pathways thermodynamically. A comprehensive analysis elucidates the electronic origins of defect-mediated performance across green ammonia synthesis (nitrogen and nitrate reduction) and advanced wastewater treatment (electro-Fenton, targeted non-radical persulfate activation, and priority pollutant electroreduction). Furthermore, this review challenges the pervasive assumption of static active sites, emphasizing how operando interrogation reveals the highly dynamic, transient nature of defect architectures under applied electrochemical bias. Finally, the frontier of artificial intelligence-guided discovery and multi-defect synergy is highlighted, charting a translational roadmap from atomic-level precision to robust industrial reactor integration. Ultimately, this review elevates defect electrocatalysis from a purely descriptive phenomenon into a predictive, quantitatively guided design discipline essential for achieving closed-loop global sustainability.
Syed Shaheen Shah, Tauqir Ahmad, Sidra Khalid, Sikandar Khan, Sami Ullah, Qaiser Khan, Md. Abdul Aziz
Renewable electricity-driven water electrolysis offers a promising route to low-emission hydrogen, yet exceptional laboratory catalyst performance does not necessarily translate into efficient, durable, and scalable electrolyzer operation. This review examines nanostructured electrocatalysts across interconnected length scales, linking atomic-level electronic structure and adsorption energetics with the potential dependent active phase, electrode transport processes, and complete device integration. Noble metal catalysts, nickel–molybdenum systems, molybdenum disulfide, nickel–iron oxyhydroxides, reconstructing precatalysts, atomically dispersed sites, and compositionally complex materials are critically assessed according to the evidence needed to identify active sites and validate long-term stability. Particular attention is given to alkaline water electrolysis, proton-exchange membrane water electrolysis, anion-exchange membrane water electrolysis, oxygen ion solid oxide electrolysis, and proton-conducting ceramic electrolysis. The review shows that apparent activity can be overstated by surface roughness, transient reconstruction, electrolyte purity, or low catalyst loading, while practical deployment is limited by catalyst layer uniformity, membrane compatibility, ion transport, water supply, gas removal, dissolution, thermal management, dynamic loading, and manufacturing constraints. A unified translation framework is proposed to distinguish mechanistic promise from device-relevant progress and guide the development of efficient, durable, resource-conscious, and verifiably low-emission hydrogen production at scale.
Joseph A. Olaniyan, Daniel Pacheco, Evangelos Miliordos
The efficient and simultaneously selective conversion of methane to methanol has been one of the most research-intensive topics in catalysis over the past decades. The weaker C-H bond of methanol promotes the production of over-oxidized species. The present computational study examines the catalytic performance of organometallic complexes with electron rich Earth abundant metals (cobalt, nickel, copper, formally negatively charged). A deliberately designed ligand is proposed to secure the negative charge on the metal and enable the formation of stable terminal metal-oxygen bonds. The ligand coordinates the metal with metal-carbon bonds, and the skeleton of the ligand is chosen to constrain the motion of the coordinated carbon atoms, avoiding the insertion of oxygen to the metal-carbon bond. We found that the energy barriers for methane activation are less than 15 kcal/mol across all three metals, and that the turnover frequency is determined by the methanol-release step, which is highly temperature-sensitive. Therefore, solvent effects and temperature can be tuned to improve the overall catalytic efficiency. The most impressive result of our study is that the activation barriers for methane and methanol are competitive (within 1–2 kcal/mol). This observation makes catalysts with electron rich metal centers unique and promising for efficient and selective conversion of methane to methanol.
