The exploration of earth‐abundant and high‐efficiency bifunctional electrocatalysts for overall water splitting is of vital importance for the future of the hydrogen economy. Regulation of electronic structure through heteroatom doping represents one of the most powerful strategies to boost the electrocatalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a rational design of O‐incorporated CoP (denoted as O‐CoP) nanosheets, which synergistically integrate the favorable thermodynamics through modification of electronic structures with accelerated kinetics through nanostructuring, is reported. Experimental results and density functional theory simulations manifest that the appropriate O incorporation into CoP can dramatically modulate the electronic structure of CoP and alter the adsorption free energies of reaction intermediates, thus promoting the HER and OER activities. Specifically, the optimized O‐CoP nanosheets exhibit efficient bifunctional performance in alkaline electrolyte, requiring overpotentials of 98 and 310 mV to deliver a current density of 10 mA cm−2 for HER and OER, respectively. When served as bifunctional electrocatalysts for overall water splitting, a low cell voltage of 1.60 V is needed for achieving a current density of 10 mA cm−2. This proposed anion‐doping strategy will bring new inspiration to boost the electrocatalytic performance of transition metal–based electrocatalysts for energy conversion applications.

Rationally generating oxygen vacancies in electrocatalysts is an important approach to modulate the electrochemical activity of a catalyst. Herein, we report a remarkable enhancement in oxygen reduction reaction (ORR) activity of NiCoO supported on hollow carbon spheres (HCS) achieved through generating abundant oxygen vacancies within the surface lattice. This catalyst exhibits enhanced ORR activity (larger limiting current density of ∼-5.8 mA cm) and higher stability (∼90% retention after 40 000 s) compared with those of NiCoO/HCS and NiCoO. The results of X-ray photoelectron spectroscopy (XPS) characterizations suggest that the introduction of oxygen vacancies optimizes the valence state of active sites. Furthermore, we carried out density functional theory (DFT) calculations to further confirm the mechanism of oxygen vacancies, and results show that oxygen vacancies enhance the density of states (DOS) near the Fermi level, decrease work function, and lower the calculated overpotential of NiCoO.

close-packed structures with lower surface energy and anisotropy, leading to great challenges in stabilizing and synthesizing 2D noble metal nanomaterials. To this end, a variety of synthetic strategies, such as hard-template-directed synthesis, capping-agent-assisted synthesis, and secondary assembly methods, have been developed for the synthesis of 2D noble metal-based nanostructures. [2] As one of the alternatives, self-assembly from 0D or 1D primary building blocks has been identified as a sophisticated and reliable approach for the generation of 2D noble metal nanostructures. [3] Ultrathin noble metal nanowires with high surface-tovolume ratios and atom utilization efficiency hold promising applications in widespread fields, including catalysis, optics devices, and biomedicine, etc. [4] Rational engineering of 1D nanowires into 2D nanosheets may bring about many novel structural characteristics, including high porosity, large area per unit volume, good flexibility, and an interconnected open pore structure. [5] Therefore, succinct-operated and controllable synthesis of ultrathin free-standing 2D nanosheets with 1D primary building blocks would be of great significance for fundamental scientific interest and technological applications, yet still remains greatly challenging.Herein, for the first time, we present a novel and facile one-pot, simultaneous stepwise self-assembly approach for the synthesis of freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) with the assistance of a functional polymer, poly(diallyldimethylammonium chloride) (PDDA; Figure S1, Supporting Information). Essentially, the obtained porous Pd nanosheets are flexibly knitted by numerous interweaved ultrathin nanowires. Different from the previously reported 2D noble metal nanosheets with smooth surface, [6,7] the obtained Pd nanosheets with large porosity and rough surface are achieved by particle spontaneous attachment and subsequent self-assembly in the one-pot synthesis process. To the best of our knowledge, this is the first report that the construction of 2D sheet-like Pd porous nanostructures through such a simple and efficient approach so far, and the elaborate adoption of eco-friendly PDDA as a structuredirecting agent also plays a crucial role in the formation of the Freestanding ultrathin 2D noble metal nanosheets have drawn enormous attention due to their potential applications in various fields. However, the synthesis of 2D noble metal nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of 2D structures. Here, a facile one-pot synthesis of ultrathin freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) flexibly knitted by interweaved ultrathin nanowires with the assistance of poly(diallyldimethylammonium chloride) is presented. Nanoparticles attachment and subsequent self-assembly in the synthetic process are responsible for the formation of such intriguing nanostructures. Moreover, finely controlling the p...

Annealing core@shell nanoparticles (NPs) yields high-entropy alloy NPs. Owing to their dispersed Pt/Pd content and low elemental diffusivity, they exhibit enhanced electrocatalytic performance and durability for the oxygen reduction reaction.

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