Recent years have witnessed an upsurge of interest in exploiting advanced photo‐/electrocatalysts for efficient energy conversion and environmental remediation. Constructing internal electric fields ...has been highlighted as a rising star to help facilitate various catalytic processes, with the merits of promoting charge transfer/separation, optimizing redox potential and creating effective active/adsorption sites. Internal electric fields are usually formed by the polarization of uneven charge distributions between different constituent layers, which widely exist in piezoelectrics, polar surface terminations, and heterostructure materials. Herein, a groundbreaking and interdisciplinary overview of the latest advances in the construction of internal electric fields to improve photo(electro)catalytic and electrocatalytic activity is provided. This critical review begins with an encyclopedic summary of the classification, advantages, and synthesis strategies of internal electric fields. Subsequently, the identification methods are thoroughly discussed based on the characterization techniques, experiments, and theoretical calculations, which can provide profound guidance for the in‐depth study of internal electric fields. To elaborate the theory–structure–activity relationships for internal electric fields, the corresponding reaction mechanisms, modification strategies, and catalytic performance are jointly discussed, along with a discussion of their practical energy and environmental applications. Finally, an insightful analysis of the challenges and future prospects for internal electric field‐based catalysts are discussed.
This review provides a clear understanding of the classification, advantages, creation, and identification of internal electric fields and the dramatic improvements in energy and environmental catalysis that result.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
As hydrogen has been increasingly considered as promising sustainable energy supply, electrochemical overall water splitting driven by highly efficient non‐noble metal electrocatalysts has aroused ...extensive attention. Transition metal phosphides (TMPs) have demonstrated remarkable electrocatalytic performance, including high activity and robust durability towards hydrogen evolution reaction (HER) in acidic and alkaline as well as neutral electrolytes. In this Review, up‐to‐date progress of TMP‐based HER electrocatalysts is summarized. Various synthesis strategies of TMPs based on selected phosphorus sources are presented, and the reaction mechanisms of HER as well as the contribution of phosphorus in the TMPs to HER activity are briefly discussed. The multiscale approaches for promoting the activity and stability of TMP‐based catalysts are discussed with respect to intrinsic electronic structure, hybrids, microstructure, and working electrode interface. Some crucial issues and future perspectives of TMPs are pointed out. These modulated approaches and challenges are also instructive for constructing other high‐activity energy‐related electrocatalysts.
Transitioning to hydrogen: In this Review, up‐to‐date progress of transition metal phosphide (TMP)‐based hydrogen evolution reaction (HER) electrocatalysts is summarized. Various synthesis strategies and the HER reaction mechanisms of TMP‐based catalysts are briefly discussed. In addition, multiscale approaches with respect to electronic structure, hybrids, microstructure, and working electrode interface are discussed for promoting HER performances.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Water splitting for the production of hydrogen and oxygen is an appealing solution to advance many sustainable and renewable energy conversion and storage systems, while the key fact depends on the ...innovative exploration regarding the design of efficient electrocatalysts. Reported herein is the growth of CoP mesoporous nanorod arrays on conductive Ni foam through an electrodeposition strategy. The resulting material of well‐defined mesoporosity and a high specific surface area (148 m2 g−1) can be directly employed as a bifunctional and flexible working electrode for both hydrogen and oxygen evolution reactions, showing superior activities as compared with noble metal benchmarks and state‐of‐the‐art transition‐metal‐based catalysts. This is intimately related to the unique nanorod array electrode configuration, leading to excellent electric interconnection and improved mass transport. A further step is taken toward an alkaline electrolyzer that can achieve a current density of 10 mA cm−2 at a voltage around 1.62 V over a long‐term operation, better than the combination of Pt and IrO2. This development is suggested to be readily extended to obtain other electrocatalysis systems for scale‐up water‐splitting technology.
Flexible, bifunctional electrodes with self‐supported CoP mesoporous nanorod arrays are fabricated through an electrodeposition strategy. The electrodes possess well‐structured mesoporosity and a high specific surface area, exhibiting high activities toward both electrochemical hydrogen and oxygen evolution reactions. In a further step, an alkaline electrolyzer with a current density of 10 mA cm−2 at 1.62 V in a long‐term operation is realized.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Photocatalytic, photoelectrochemical and electrocatalytic water splitting provide advanced approaches to produce green hydrogen as a sustainable and renewable energy carrier. The development of ...highly efficient catalysts is the key to achieving cost-effective and large-scale production of hydrogen. Recently, P-containing catalysts have gained a great deal of attention owing to their diverse chemical valence states, tunable structure and unique physicochemical properties. In this review, an overview of up-to-date progress in water splitting of P-containing photo- and electro-catalysts including elemental P, transition metal phosphides, metal phosphates/phosphonates and metal phosphorus trichalcogenides is provided. A general introduction to the water splitting mechanism and the activity origin of P-containing catalysts is briefly presented to provide rational guidance for the design of highly efficient catalysts. Notably, innovational strategies to design P-containing catalysts with enhanced catalytic activity are summarized with respect to modifying the phase, introducing foreign elements, tailoring morphology and engineering interfaces. In each section, we aim to deeply clarify the theory-structure-property relationship and provide underlying reasons behind enhanced catalytic performance. Finally, some challenges and research orientations of P-containing catalysts toward water splitting are briefly proposed from the perspectives of practical application and mechanism investigation.
The innovational strategies to design P-containing catalysts with enhanced photo-/electro-catalytic water splitting activity are reviewed with respect to phase modifying, foreign elements introducing, morphology tailoring and interface engineering.
Water electrolysis, driven by renewable energy resources, is a promising energy conversion technology that has gained intensive interest in recent years. However, conventional water electrolysis ...faces a number of challenges, including large thermodynamic potential gaps, valueless anodic products, explosive hydrogen/oxygen mixtures, reactive oxygen species, and limited pure water. Hybrid water electrolysis, appending different electrolytes in the anode compartment to circumvent the above‐mentioned challenges in conventional water electrolysis, is a particularly attractive alternative. In this review, for the first time, a holistic and subtle description of hybrid water electrolysis is provided, focusing on the design of high‐activity/selectivity/stability anodic electrocatalysts for the electrochemical oxidation of various chemicals, such as alcohol, aldehyde, amine, urea and hydrazine, or the oxygen evolution reaction in seawater electrolytes. Comprehensive judging criteria for anodic oxidation reactions, electrocatalysts, and reaction parameters in hybrid water electrolysis are discussed. Some technoeconomic assessments, feasibility analyses, mechanism explorations, and correlation comparisons are involved. Finally, perspectives on and opportunities for future research directions in hybrid water electrolysis systems are outlined.
Hybrid water electrolysis can circumvent the challenges of conventional water electrolysis and show several advantages, including energy efficiency, cost, and safety. Based on the considerations of alternative oxidation reactions, electrocatalysts and reaction parameters for hybrid water electrolysis, several judging criteria are proposed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing ...chlorine evolution, and catalyst poisoning. Hereto, the core‐shell‐structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni3S2 nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000 mA cm−2 at the overpotential of 341 mV in 1.0 m KOH seawater. The feasible surface reconstruction of Ni3S2‐FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni3S2 nanopyramids coated with FeNi2P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0 m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636 V to attain 100 mA cm−2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater.
Herein, core‐shell structured Ni3S2‐FeNi layer double hydroxides (LDH) heterointerfaces are rationally prepared. Abundant hydroxide/sulfide interfaces boost alkaline water oxidation. Impressively, electrochemical results indicate that the in situ formed sulfate layer in LDH shell largely enhances the corrosion resistance of the catalysts in the alkaline salty‐water electrolytes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Graphitic carbon nitride (g-C3N4) has been deemed a promising heterogeneous metal-free catalyst for a wide range of applications, such as solar energy utilization toward water splitting, and its ...photocatalytic performance is reasonably adjustable through tailoring its texture and its electronic and optical properties. Here phosphorus-doped graphitic carbon nitride nanostructured flowers of in-plane mesopores are synthesized by a co-condensation method in the absence of any templates. The interesting structures, together with the phosphorus doping, can promote light trapping, mass transfer, and charge separation, enabling it to perform as a more impressive catalyst than its pristine carbon nitride counterpart for catalytic hydrogen evolution under visible light irradiation. The catalyst has low cost, is environmentally friendly, and represents a potential candidate in photoelectrochemistry.
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IJS, KILJ, NUK, PNG, UL, UM
Small ZnO nanoclusters supported on dealuminated β zeolite were prepared and evaluated for catalyzing direct dehydrogenation of propane to propylene (PDH), exhibiting high catalytic performance. N2 ...sorption, XRD, TEM, 27Al and 28Si MAS NMR, IR, XRF, DR UV‐vis, XPS, and NH3‐TPD techniques were employed to characterize the physicochemical properties of this novel catalyst system. It is found that the Zn species can be accommodated in the vacant T‐atom sites of dealuminated β zeolite due to the reaction of aqueous zinc acetate solution with silanol groups, and thus, producing massive small ZnO nanoclusters as active phases in PDH. Additionally, dealuminated β zeolite can greatly depress side reactions attributable to the absence of strong acid sites, thereby guaranteeing high catalytic activity, propylene selectivity and stability. As a result, the optimal catalyst of 10 wt% Zn loaded on dealuminated β zeolite exhibits a high initial propane conversion of around 53 % and a superior propylene selectivity of about 93 % at a space velocity of 4000 cm3 gcat−1 h−1, together with the high stability and satisfactory reusability. This study may open a new way to design and synthesize highly active PDH catalysts with high selectivity and stability.
Catalysts with Zing: Small ZnO nanoclusters supported on dealuminated β zeolite can be obtained via a two‐step post‐synthesis method, showing much better catalytic performance for direct dehydrogenation of propane to propylene than that on raw Hβ zeolite.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Rational design and preparation of economical, high-efficiency, and robust electrocatalysts for the reversible oxygen reduction and evolution reactions to substitute noble-metal electrocatalysts are ...significantly vital for the development of electrocatalytic energy conversion technologies. Metal modified N-doped carbon materials have attracted tremendous interest due to the evidently improved activities and fascinating features, whereas the development of facile and efficient fabrication methodologies is still highly challenging. Herein, we elaborately developed a reliable and scalable graphitic carbon nitride (g-C
3
N
4
)-templated method to prepare uniformly dispersed N-coordinated metal (M = Fe, Co, Ni, Cu, Mn, Mo and Sn) species in porous carbon nanosheets (M-N-C PCSs) using cost-effective and sustainable polyacrylonitrile (PAN) as a heteroatom precursor and carbon source. With the assembly of sufficiently distributed N-coordinated metal species, and advanced porous nanosheet architectures, the as-synthesized M-N-C PCSs, especially Fe-N-C PCSs, exhibit an outstanding catalytic efficiency for both oxygen reduction and evolution reactions in an alkaline medium, even competing with the state-of-the-art Pt/C catalysts and recently reported highly active non-noble electrocatalysts, thus possessing an ability to work as an air cathode for rechargeable Zn-air batteries with a large peak power density and high long-term durability. This reported synthesis approach will provide novel but facile guidance to the exploration and preparation of various porous carbon materials with an outstanding efficiency for diverse energy systems.
Highly porous carbon nanosheets with N-coordinated metals are rationally developed and show outstanding electrocatalytic oxygen reduction and oxygen evolution performance.
The electrocatalytic splitting of water holds great promise as a sustainable and environmentally friendly technology for hydrogen production. However, the sluggish kinetics of the oxygen evolution ...reaction (OER) at the anode significantly hampers the efficiency of this process. In this comprehensive perspective, we outline recent advancements in innovative strategies aimed at improving the energy and economic efficiency of conventional water electrolysis, thereby facilitating efficient hydrogen generation. These novel strategies mainly include: (i) sacrificial-agent-assisted water electrolysis, which integrates thermodynamically favorable small molecules to replace the OER while simultaneously degrading pollutants; (ii) organic upgrading-assisted water electrolysis, wherein thermodynamically and kinetically favorable organic oxidation reactions replace the OER, leading to the production of high-value chemicals alongside hydrogen; (iii) self-powered electrolysis systems, achieved by coupling water splitting with metal-based batteries or fuel cells, enabling hydrogen production without the need for additional electricity input; and (iv) self-catalyzed electrolysis systems driven by the spontaneous metal oxidation at the anode, which provides electrons for hydrogen evolution at the cathode. In particular, we emphasize the design of electrocatalysts using non-noble metal elements, elucidate the underlying reaction mechanisms, and explore the construction of efficient electrolyzers. Additionally, we discuss the prevailing challenges and future prospects, aiming to foster the development of electrocatalytic systems for highly efficient hydrogen production from water in the future.
This perspective highlights recent advancements in innovative strategies to provide valuable insights into the potential for energy-saving hydrogen production through water electrolysis.
