Atomically Thin Holey Two-Dimensional Ru₂P Nanosheets for Enhanced Hydrogen Evolution Electrocatalysis

The defect engineering of low-dimensional nanostructured materials has led to increased scientific efforts owing to their high efficiency concerning high-performance electrocatalysts that play a crucial role in renewable energy technologies. Herein, we report an efficient methodology for fabricating atomically thin, holey metal-phosphide nanosheets with excellent electrocatalyst functionality. Two-dimensional, subnanometer-thick, holey Ru2P nanosheets containing crystal defects were synthesized via the phosphidation of monolayer RuO2 nanosheets. Holey Ru2P nanosheets exhibited superior electrocatalytic activity for the hydrogen evolution reaction (HER) compared to that exhibited by nonholey Ru2P nanoparticles. Further, holey Ru2P nanosheets exhibited overpotentials of 17 and 26 mV in acidic and alkaline electrolytes, respectively. Thus, they are among the best-performing Ru–P-based HER catalysts reported to date. In situ spectroscopic investigations indicated that the holey nanosheet morphology enhanced the accumulation of surface hydrogen through the adsorption of protons and/or water, resulting in an increased contribution of the Volmer–Tafel mechanism toward the exceptional HER activity of these ultrathin electrocatalysts

Interface Engineering of Oxygen Vacancy-Enriched Ru/RuO₂–Co₃O₄ Heterojunction for Efficient Oxygen Evolution Reaction in Acidic Media

RuO2 is currently regarded as a benchmark electrocatalyst for water oxidation in acidic media. However, its wide application is still restricted by limited durability and high cost. Herein, we report a Ru/RuO2–Co3O4 catalyst for boosting the acidic oxygen evolution reaction catalytic performance via constructing a heterointerface between RuO2 and Co3O4 and vacancy engineering. The resulting Ru/RuO2–Co3O4 shows a 226 mV overpotential at 10 mA cm–2 and excellent stability with a small overpotential increase after continuous testing for 19 h, greatly surpassing that of commercial RuO2 in a 0.1 M HClO4 solution. Depth structure characterizations involved in XPS, XANES, and EXAFS indicate that the favorable catalytic performance of Ru/RuO2–Co3O4 is mainly ascribed to the interfacial charge transfer by heterojunction interfaces between Co species and Ru species. Co3O4 is adjacent to RuO2 and donates electrons, making the valence state of Ru lowered and the Ru–O covalency weakened, which greatly suppress the dissolution of Ru and thus enhance stability. Meanwhile, the existing oxygen vacancies improve the intrinsic catalytic activity. This study is highly expected to favor the design and synthesis of more highly efficient electrocatalysts applied in energy-related devices

Sm-Induced Symmetry-Broken Ru Centers for Boosting Acidic Water Oxidation

Ruthenium oxide (RuO2) as a promising acidic oxygen evolution reaction (OER) electrocatalyst for proton exchange membrane water electrolyzers still suffers from severe excessive oxidation and Ru dissolution, leading to the loss of activity. Herein, a Sm doping in amorphous/crystalline heterophase RuO2 (AC-Sm-RuO2) catalyst is designed for boosting the acidic OER catalytic performance by altering the electronic properties and number of active sites. The representative AC-Sm-RuO2 displays robust OER performance with an overpotential of 200 mV to achieve 10 mA cm–2, and significantly enhanced stability compared to synthesized RuO2 (S-RuO2) and commercial RuO2 (Com. RuO2). Electrochemical measurements combined with advanced characterizations reveal that the high activity in AC-Sm-RuO2 originated from the symmetry-broken Ru active sites, which lowers the formation energy barrier of *OOH; meanwhile, the improved stability arises from the strong interplay within the local Ru–O–Sm units and the characteristics of the amorphous/crystalline hybrid. This work emphasizes the effective means to design high-performance acidic OER catalysts via the synergy of microstructure symmetry disturbance and crystal phase engineering

Synergistic Effect of Electronic Particle–Support Interactions on the Ir-Based Multiheterostructure for Acidic Water Oxidation

Exploiting durable electrocatalysts with high specific activity for acidic water oxidation is a great challenge due to the high energy barrier for the multiple oxygen evolution reaction (OER) intermediates. Deliberately taking advantage of the synergistic effect of electronic particle–support interactions on both the particle and support may address this concern. Here, we deliberately design a multiheterostructure with an IrO2 shell-coated Ir core anchored on the Co3O4 framework as an efficient acidic OER electrocatalyst. Detailed characterizations (depth-resolved XPS, XANES, and EXAFS) of the electrocatalysts demonstrate that the electronic particle–support interactions lead to a unique electron transfer at the interface from IrO2 and Co3O4 to Ir. Such an electron transfer will result in compressed Ir–O bonds and Co–O bonds, thus simultaneously reducing free energies for OER intermediates on the surfaces of both IrO2 and Co3O4, sufficiently stimulating the synergistic effect to enhance OER activity and stability

Intrabasal Plane Defect Formation in NiFe Layered Double Hydroxides Enabling Efficient Electrochemical Water Oxidation

Defect engineering has proven to be one of the most effective approaches for the design of high-performance electrocatalysts. Current methods to create defects typically follow a top-down strategy, cutting down the pristine materials into fragmented pieces with surface defects yet also heavily destroying the framework of materials that imposes restrictions on the further improvements in catalytic activity. Herein, we describe a bottom-up strategy to prepare free-standing NiFe layered double hydroxide (LDH) nanoplatelets with abundant internal defects by controlling their growth behavior in acidic conditions. Our best-performing nanoplatelets exhibited the lowest overpotential of 241 mV and the lowest Tafel slope of 43 mV/dec for the oxygen evolution reaction (OER) process, superior to the pristine LDHs and other reference cation-defective LDHs obtained by traditional etching methods. Using both material characterization and density functional theory (DFT) simulation has enabled us to develop relationships between the structure and electrochemical properties of these catalysts, suggesting that the enhanced electrocatalytic activity of nanoplatelets mainly results from their defect-abundant structure and stable layered framework with enhanced exposure of the (001) surface

Coiled Conformation Hollow Carbon Nanosphere Cathode and Anode for High Energy Density and Ultrafast Chargeable Hybrid Energy Storage

Lithium-ion batteries and pseudocapacitors are nowadays popular electrochemical energy storage for many applications, but their cathodes and anodes are still limited to accommodate rich redox ions not only for high energy density but also sluggish ion diffusivity and poor electron conductivity, hindering fast recharge. Here, we report a strategy to realize high-capacity/high-rate cathode and anode as a solution to this challenge. Multiporous conductive hollow carbon (HC) nanospheres with microporous shells for high capacity and hollow cores/mesoporous shells for rapid ion transfer are synthesized as cathode materials using quinoid:benzenoid (Q:B) unit resins of coiled conformation, leading to ∼5-fold higher capacities than benzenoid:benzenoid resins of linear conformation. Also, Ge-embedded Q:B HC nanospheres are derived as anode materials. The atomic configuration and energy storage mechanism elucidate the existence of mononuclear GeOx units giving ∼7-fold higher ion diffusivity than bulk Ge while suppressing volume changes during long ion-insertion/desertion cycles. Moreover, hybrid energy storage with a Q:B HC cathode and Ge–Q:B HC anode exploit the advantages of capacitor-type cathode and battery-type anode electrodes, as exhibited by battery-compatible high energy density (up to 285 Wh kg–1) and capacitor-compatible ultrafast rechargeable power density (up to 22 600 W kg–1), affording recharge within a minute

Coiled Conformation Hollow Carbon Nanosphere Cathode and Anode for High Energy Density and Ultrafast Chargeable Hybrid Energy Storage

Lithium-ion batteries and pseudocapacitors are nowadays popular electrochemical energy storage for many applications, but their cathodes and anodes are still limited to accommodate rich redox ions not only for high energy density but also sluggish ion diffusivity and poor electron conductivity, hindering fast recharge. Here, we report a strategy to realize high-capacity/high-rate cathode and anode as a solution to this challenge. Multiporous conductive hollow carbon (HC) nanospheres with microporous shells for high capacity and hollow cores/mesoporous shells for rapid ion transfer are synthesized as cathode materials using quinoid:benzenoid (Q:B) unit resins of coiled conformation, leading to ∼5-fold higher capacities than benzenoid:benzenoid resins of linear conformation. Also, Ge-embedded Q:B HC nanospheres are derived as anode materials. The atomic configuration and energy storage mechanism elucidate the existence of mononuclear GeOx units giving ∼7-fold higher ion diffusivity than bulk Ge while suppressing volume changes during long ion-insertion/desertion cycles. Moreover, hybrid energy storage with a Q:B HC cathode and Ge–Q:B HC anode exploit the advantages of capacitor-type cathode and battery-type anode electrodes, as exhibited by battery-compatible high energy density (up to 285 Wh kg–1) and capacitor-compatible ultrafast rechargeable power density (up to 22 600 W kg–1), affording recharge within a minute

Spinel-Anchored Iridium Single Atoms Enable Efficient Acidic Water Oxidation via Intermediate Stabilization Effect

Iridium oxide is considered the only practical catalyst for oxygen evolution reaction (OER) in commercial proton exchange membrane (PEM) electrolyzers. However, its low activity and high cost greatly hinder the large-scale development of PEM electrolyzers for hydrogen production. Herein, we report atomically dispersed Ir atoms incorporated into a spinel Co3O4 lattice as an acidic OER catalyst, which exhibits excellent activity and stability for water oxidation. The catalyst significantly lowers the overpotential down to 226 mV at 10 mA cm–2 with an ultrahigh turnover frequency value of 3.15 s–1 (η = 300 mV), 3 orders of magnitude higher than that of commercial IrO2. Meanwhile, the catalyst shows superior corrosion resistance in an acidic OER condition, reaching a lifespan of up to 500 h at 10 mA cm–2. First-principles calculations reveal that the key *OOH intermediate can be stabilized by the lattice oxygen coordinated to the Ir active site via hydrogen bond formation, which substantially regulates the rate-limiting step and lowers the activation free energy of the OER process. This work demonstrates a strategy for improving the OER activity of Ir-based catalysts and provides insights into the regulation of the reaction mechanism