Catalytic coordinates are essentially the dynamic interactions of frontier orbitals when interacting with electrocatalysts and adsorbates under optimal reaction conditions. Flexible modifications in orbital hybridization enable intrinsic control over both the thermodynamics and kinetics of electrochemical reactions. However, systematic depictions of this phenomenon in electrocatalysis are currently lacking, despite being extremely important. In this tutorial review, a comprehensive interpretation of orbital hybridization involved in the catalyst system and its role in electrocatalysis is provided. This review starts with the fundamentals of orbital hybridization, covering basic theories (valence bond theory, hybrid orbit theory, molecular orbital theory, and frontier orbital theory), classifications (binary‐ and multi‐orbital interactions), and descriptors (such as orbital overlap degree, energy level matching, and Fermi energy level). It further introduces the key roles of orbital hybridization in manipulating the intrinsic activity, selectivity, and stability of electrocatalysts, as well as extending the device lifespan. Recent advances in tuning orbital hybridization for enhanced electrochemical reactions (e.g., HER, OER, ORR, NRR, and CO2RR) through various strategies (external field modulation, electronic structure modulation, geometric structure modulation, and coordination microenvironment regulation). Challenges and perspectives for future research related to orbital hybridization are discussed at the end.

P-block metal-based catalysts are an emerging, effective, and sustainable alternative to precious metal electrocatalysts for energy conversion. These p-block-based materials exhibit unique characteristics, such as oxophilicity, weak hydrogen adsorption, and flexible electronic tuning, which rival those of Pt-group metals. Several morphologies (single-atom catalysts, pure metals, alloys, compounds, and doped systems) have achieved remarkable catalytic efficiencies and selectivity utilizing p-block metals. Recent advances have focused on tailoring the electronic band, surface morphology, and coordination environments, significantly enhancing catalytic stability and activity. Mechanistic studies highlight deviations from traditional d-band scaling relationships, offering novel design strategies for reaction-specific optimization. However, challenges remain. Achieving industrially relevant current densities, long-term stability, and scalable synthesis remains troublesome. This review synthesizes recent progress in p-block metal-based electrocatalysts across various morphologies to identify performance and mechanistic trends for energy conversion applications (e.g., oxygen reduction, nitrate reduction, and carbon dioxide reduction reactions). Critical research directions are identified, and fundamental gaps in p-block metal research are discussed. By establishing the core understanding, future research can focus on untapping the potential of p-block metals for next-generation electrocatalysts.Full Tex

Palladium (Pd)‐based catalysts are considered compelling alternatives to platinum (Pt)‐based counterparts in various electrocatalytic reactions. Recently, Pd metallene‐based nanomaterials have emerged as innovative materials for electrocatalysis, demonstrating unique functional properties and exceptional catalytic activity. This review aims to discuss recent research progress on Pd metallene‐based electrocatalysts for energy conversion applications, providing an overview of their design strategies and pivotal advantages. Seven pivotal construction strategies for Pd metallene‐based electrocatalysts, including defect engineering, interface engineering, strain effect, phase engineering, alloying effect, and doping effect, are meticulously introduced and comprehensively discussed, highlighting their critical roles in modulating the electronic structure and coordination environment. Finally, the current challenges and perspectives on the future directions of Pd metallene‐based electrocatalysts are provided.

Polyoxometalates (POMs) are polyatomic ions with closed three-dimensional frameworks. Their unique structure contains a large number of redox active sites, making them promising electrocatalysts for electrochemical energy conversion and storage applications. Thus, this paper presents an overview of the use of POMs as electrocatalysts for electrochemical energy conversion and storage devices, such as batteries, supercapacitors, fuel cells, or water electrolyzers. A discussion of the viability of these materials as alternatives to noble metal-based electrocatalysts is made. The current status of these materials to respond to the challenges of converting modern energy systems into more sustainable ones is also envisaged

Photocatalysis and electrocatalysis have emerged as promising technologies for addressing the energy crisis and environmental issues. However, the widespread application of these technologies is hampered by the challenge of scaling up the production of photo/electrocatalysts that are not only highly active and stable but also cost‐effective and environmentally benign. This review delves into the latest advancements in the large‐scale synthesis of photo/electrocatalysts. The factors to be considered in the large‐scale production of catalysts are discussed first. The synthesis methods for batch preparation of photo/electrocatalysts are then comprehensively introduced, with a thorough discussion of their respective advantages and limitations. Moreover, the data analysis via machine learning techniques, which not only accelerates the identification and refinement of potential new catalysts but also offers insights for enhancing the high‐throughput synthesis of catalysts, is introduced in detail. Then the representative examples are presented to illustrate the applications of large‐scale catalysts in the field of industrial‐level photo/electrocatalysis. Finally, the challenges and prospects in the development of large‐scale production of photo/electrocatalysts are discussed. By bridging the gap between laboratory research and industrial application, this review aims to provide a reference for the future of large‐scale preparation of photo/electrocatalysts in sustainable energy conversion and beyond.

Clusters (<10 nm) with dimensions between molecules and nanoparticles are emerging materials with enormous potential, mainly for catalytic applications. They behave like superatoms, with exciting sizes and facet-dependent and dynamic intrinsic properties. They also have showed improved activity for a variety of electrochemical applications, including water splitting, CO 2 reduction reaction, and N 2 reduction reaction. In this chapter, we aim to discuss the clusters in terms of their unique physicochemical properties, cluster size effects, cluster composition, cluster-support interactions, and various recent advances in electrochemical energy conversion applications. Moreover, we will discuss the existing challenges and future prospects of enhancing the performance of cluster-based electrocatalysts

Abstract MXenes, due to their tailorable chemistry and favourable physical properties, have great promise in electrocatalytic energy conversion reactions. To exploit fully their enormous potential, further advances specific to electrocatalysis revolving around their performance, stability, compositional discovery and synthesis are required. The most recent advances in these aspects are discussed in detail: surface functional and stoichiometric modifications which can improve performance, Pourbaix stability related to their electrocatalytic operating conditions, density functional theory and advances in machine learning for their discovery, and prospects in large scale synthesis and solution processing techniques to produce membrane electrode assemblies and integrated electrodes. This Review provides a perspective that is complemented by new density functional theory calculations which show how these recent advances in MXene material design are paving the way for effective electrocatalysts required for the transition to integrated renewable energy systems.

Carboxydothermus hydrogenoformans is a thermophilic strictly anaerobic bacterium that catalyses the water gas shift reaction, the conversion of carbon monoxide with water to molecular hydrogen and carbon dioxide. The thermodynamically favorable growth temperature, compared to existing industrial catalytic processes, makes this organism an interesting alternative for production of cheap hydrogen gas suitable to fuel CO-sensitive fuel cells in a future hydrogen economy, provided sufficiently low levels of CO are reached. Here we study CO conversion and final CO levels in cultures of C. hydrogenoformans grown in batch cultures that were started with a 100% CO gas phase with and without removal of formed CO2. Final CO levels were 117 ppm without CO2 removal and below 2 ppm with CO2 removal. The Gibbs free energy change calculated with measured end concentrations and the detection of acetate suggest that C. hydrogenoformans shifted from a hydrogenogenic to an acetogenic metabolism

The need for enhanced energy storage and improved catalysts has led researchers to explore advanced functional materials for sustainable energy production and storage. Herein, we demonstrate a reductive electrosynthesis approach to prepare a layer-by-layer (LbL) assembled trimetallic Fe-Co-Ni metal-organic framework (MOF) in which the metal cations within each layer or at the interface of the two layers are linked to one another by bridging 2-amino-1,4-benzenedicarboxylic acid linkers. Tailoring catalytically active sites in an LbL fashion affords a highly porous material that exhibits excellent trifunctional electrocatalytic activities toward the hydrogen evolution reaction (ηj=10 = 116 mV), oxygen evolution reaction (ηj=10 = 254 mV), as well as oxygen reduction reaction (half-wave potential = 0.75 V vs reference hydrogen electrode) in alkaline solutions. The dispersion-corrected density functional theory calculations suggest that the prominent catalytic activity of the LbL MOF toward the HER, OER, and ORR is due to the initial negative adsorption energy of water on the metal nodes and the elongated O-H bond length of the H2O molecule. The Fe-Co-Ni MOF-based Zn-air battery exhibits a remarkable energy storage performance and excellent cycling stability of over 700 cycles that outperform the commercial noble metal benchmarks. When assembled in an asymmetric device configuration, the activated carbon||Fe-Co-Ni MOF supercapacitor provides a superb specific energy and a power of up to 56.2 W h kg-1 and 42.2 kW kg-1, respectively. This work offers not only a novel approach to prepare an LbL assembled multimetallic MOF but also provides a benchmark for a multifunctional electrocatalyst for water splitting and Zn-air batteries.

This paper deals with a hierarchical structure composed by an event-based supervisor in a higher level and two distinct proportional integral (PI) controllers in a lower level. The controllers are applied to a variable speed wind energy conversion system with doubly-fed induction generator, namely, the fuzzy PI control and the fractional-order PI control. The event-based supervisor analyses the operation state of the wind energy conversion system among four possible operational states: park, start-up, generating or brake and sends the operation state to the controllers in the lower level. In start-up state, the controllers only act on electric torque while pitch angle is equal to zero. In generating state, the controllers must act on the pitch angle of the blades in order to maintain the electric power around the nominal value, thus ensuring that the safety conditions required for integration in the electric grid are met. Comparisons between fuzzy PI and fractional-order PI pitch controllers applied to a wind turbine benchmark model are given and simulation results by Matlab/Simulink are shown. From the results regarding the closed loop point of view, fuzzy PI controller allows a smoother response at the expense of larger number of variations of the pitch angle, implying frequent switches between operational states. On the other hand fractional- order PI controller allows an oscillatory response with less control effort, reducing switches between operational states

Biomass is a low-cost, abundant and renewable resource that can be used to manufacture porous carbon-based materials for a variety of applications. Different mesoporous carbon supports can be obtained from the various synthetic approaches that are aimed at increasing the specific surface area and functionalization. Currently, most of the biomass is used for energy recovery. The circular economy approach could lead to the development of cheap and sustainable materials, and turning of wastes into a precious resource. In this review, we provide the recent advances in the field of electrochemistry for porous carbon materials derived from biomass, which offers wider applications in proton exchange membrane fuel cells (PEMFCs), anion exchange membrane fuel cells (AEMFCs) and Zn-air batteries (ZABs). The focus is on understanding the required properties of the materials and the role of synthetic pathways in platinum group metal (PGM) free electrocatalysts. The most promising materials are evaluated towards the oxygen reduction reaction (ORR) in PEMFC, AEMFC, and ZAB. The results achieved showed that the expected performances on these energy conversion devices still lack for deployment in practice, especially if compared with commercially available PGM-free electrocatalysts. This review article provides insights on how to improve the actual electrocatalytic activity of biomass-derived materials.

The successful commercialization of advanced energy devices, including fuel cells and solar cells (e.g., dye-sensitized solar cells) is somewhat dependent on the cost, activity and durability of the electrocatalysts. Nowadays, precious metal electrodes are the most widely used. Accordingly, the manufacturing costs are relatively high, which constrains wide application. Recently, some reports have introduced some promising non-precious electrocatalysts to be exploited in both oxidation and reduction reactions. It was concluded that immobilization of the functional material on a proper support can distinctly improve catalytic activity. Moreover, due to the synergetic effect, metallic alloy nanoparticles show very good electrocatalytic activity in this regard. This Special Issue aims to cover the most recent progress and the advances in the field of the immobilized non-precious electrocatalysts. This includes, but is not limited to, non-precious electrocatalysts for alcohol (methanol, ethanol, etc.) oxidation, oxygen reduction reaction and electrolyte reduction in dye-sensitized solar cells

Electrochemical and thermochemical conversion of CO2 into fuels are significant carbon conversion technologies to mitigate carbon emissions. Based on the captured CO2, many previous studies carried out tech-economic and environmental analyses for the CO(2 )conversion systems. However, it is unclear about the energy efficiency and emission reduction of the full-chain system after applying carbon conversion technologies to the carbon sources such as coal power plants and chemical industries. With a unified coal-fired power plant as the carbon source, this study conducted a full-chain systematic analysis of three representative CO2 conversion technologies (shown as routes 1, 2, and 3). Routes 1, 2, and 3 converted the emitted CO2 into fuels via CO2 electrolysis, MEA-CO2 electrolysis, and CO2 hydrogenation. The performance of three Routes in terms of energy efficiency and carbon emissions was comprehensively analyzed. And this work also investigated the energy efficiency improvement potential of three Routes. The results indicated that the energy efficiency of Route 1 was the greatest. And Route 2 exhibited optimal emission reduction. The core factors for enhancing the performance of full-chain systems were improving the efficiency of photovoltaic power generation and developing low-energy-consumption CO2 absorbents. The results also indicated that to date, from the perspective of converting CO2 into the fuel gas CO, no Routes had advantages over coal power plants with carbon capture and storage (CCS) or syngas production directly from coal gasification in terms of energy efficiency and carbon emissions. However, converting CO2 into high-value-added products might be more significant for integrating carbon emission reduction and storing renewable electricity

Efficient energy conversion and storage applications (e.g. liquid fuel cell and water splitting) have been identified as promising solutions to future energy depletion. However, practical installation of energy conversion and storage applications is impeded by the low performance and high cost of electrocatalysts. Therefore, it is imperative to improve the electrocatalysts’ performance so as to decrease the overall cost. The objective of this thesis is to design and synthesize electrocatalysts for energy conversion and storage applications. To this end, several works have been conducted. First, 3D Palladium nanoarchitectures were prepared, with abundant catalytic sites and open space for electrooxidation of formic acid. Second, overpotential for hydrogen evolution was lowered by fabricating two dimensional Co/NC. Third, a hybrid of MOFs was fabricated for introducing synergistic effect towards oxygen evolution. Lastly, a heterostructure of layered double hydroxides was produced for electrochemical oxygen evolution.Doctor of Philosoph

Since Boudart???s pioneering work on the use of tungsten carbide as a non-precious metal catalyst for some important catalytic reactions, metal carbides have attracted continuous interest in heterogeneous catalysis. With ever-increasing importance of hydrogen-based energy cycle, metal carbides have received increasing attention as alternative electrocatalysts for Pt-group metal catalysts in renewable energy conversion reactions. This Mini-review provides recent advances in transition metal carbide (TMC)-catalyzed energy conversion reactions. We summarize major attributes of TMCs as electrocatalysts and highlight structural design and reactivity of TMCs for hydrogen-, oxygen-, and carbon-involving energy conversion reactions with notable examples. We also describe future challenges and opportunities of TMC electrocatalysts in this field

Energy’s efficient conversion and storage are closely correlated to the development of electrochemical energy technologies, such as fuel cells, batteries, electrolyzers, etc [...]

The production of hydrogen through electrochemical water splitting driven by clean energy becomes a sustainable route for utilization of hydrogen energy, while an efficient hydrogen evolution reaction (HER) electrocatalyst is required to achieve a high energy conversion efficiency. Nickel phosphides have been widely explored for electrocatalytic HER due to their unique electronic properties, efficient electrocatalytic performance, and a superior anti-corrosion feature. However, the HER activities of nickel phosphide electrocatalysts are still low for practical applications in electrolyzers, and further studies are necessary. Therefore, at the current stage, a specific comprehensive review is necessary to focus on the progresses of the nickel phosphide electrocatalysts. This review focuses on the developments of preparation approaches of nickel phosphides for HER, including a mechanism of HER, properties of nickel phosphides, and preparation and electrocatalytic HER performances of nickel phosphides. The progresses of the preparation and HER activities of the nickel phosphide electrocatalysts are mainly discussed by classification of the preparation method. The comparative surveys of their HER activities are made in terms of experimental metrics of overpotential at a certain current density and Tafel slope together with the preparation method. The remaining challenges and perspectives of the future development of nickel phosphide electrocatalysts for HER are also proposed