Exploring highly active and inexpensive bifunctional electrocatalysts for water‐splitting is considered to be one of the prerequisites for developing hydrogen energy technology. Here, an efficient simultaneous etching‐doping sedimentation equilibrium (EDSE) strategy is proposed to design and prepare hollow Rh‐doped CoFe‐layered double hydroxides for overall water splitting. The elaborate electrocatalyst with optimized composition and typical hollow structure accelerates the electrochemical reactions, which can achieve a current density of 10 mA cm−2 at an overpotential of 28 mV (600 mA cm−2 at 188 mV) for hydrogen evolution reaction (HER) and 100 mA cm−2 at 245 mV for oxygen evolution reaction (OER). The cell voltage for overall water splitting of the electrolyzer assembled by this electrocatalyst is only 1.46 V, a value far lower than that of commercial electrolyzer constructed by Pt/C and RuO2 and most reported bifunctional electrocatalysts. Furthermore, the existence of Fe vacancies introduced by Rh doping and the typical hollow structure are demonstrated to optimize the entire HER and OER processes. EDSE associates doping with template‐directed hollow structures and paves a new avenue for developing bifunctional electrocatalysts for overall water splitting. It is also believed to be practical in other catalysis fields as well.

Rationally designing efficient and robust catalysts for the oxygen evolution reaction (OER) is increasingly vital for energy conversion technologies. Herein, we develop a core–shell electrocatalyst consisting of an amorphous/crystalline heterophase NiFe alloy encapsulated by ultrathin graphene layers (a/c-NiFe-G) via a rapid microwave thermal shock strategy. The amorphous/crystalline heterostructure generates enriched active sites with high intrinsic activity, while the graphene coatings serve as electron transport pathways and protective layers, resulting in dramatically enhanced OER performance in 1 M KOH with an overpotential (η10) of 250 mV at 10 mA cm–2, a Tafel slope of 36.5 mV dec–1, a high turnover frequency (TOF) of 0.87 s–1 that is 24 times as high as that of the crystalline counterpart when evaluated on a glassy carbon electrode. Further, when supported on porous Ni foam, the catalyst exhibited an η10 as low as 217 mV, along with excellent durability (136 h). Various characterization methods, including X-ray absorption fine structure analysis and density functional theory calculations, reveal that unsaturated coordination configurations and abundant amorphous/crystalline boundaries in a/c-NiFe-G are responsible for its superior OER performance. This work offers insights for constructing metastable amorphous/crystalline heterophase catalysts toward highly efficient electrocatalysis.

Metal‐ and nitrogen‐doped carbon (M–N–C) materials as a unique class of single‐atom catalysts (SACs) have increasingly attracted attention as the replacement of platinum for the hydrogen evolution reaction (HER); however, their employment as HER electrodes at high current densities of industrial level remains a grand challenge. Herein, an aligned porous carbon film embedded with single‐atom Co–N–C sites of exceptional activity and stability at high current densities is designed. Within the film, the atomic CoNx moieties exhibit high intrinsic activity, while the multiscale porosity of the carbon frameworks with vertically aligned microchannels afford facilitated mass transfer under the conditions of high production rate and ultrathick electrodes. Moreover, the superwetting properties of the film promote electrolyte wetting and ensure the timely removal of the evolving H2 gas bubbles. The as‐designed film can work as an efficient HER electrode to deliver 500 and 1000 mA cm−2 in acid at overpotentials of 272 and 343 mV, respectively, and can operate uninterruptedly and stably at 1000 mA cm−2 for at least 32 h under static conditions. These findings pave the road toward the rational design of SACs with improved activity and stability at high current densities in gas‐evolving electrocatalytic processes.

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Charge and mass transfer at the interface between electrode and electrolyte are of vital significance for energy conversion and storage in aqueous rechargeable zinc ion batteries (ZIBs). Approaching rational design and preparation of unique nanostructures with enhanced mass transfer is still facing great challenges in response to these problems. Herein, the highly uniform and round new‐state nsutite‐type vanadium dioxide (VO2) nanoplates with novel ancient Chinese coin structure (with thickness of ≈50 nm and diameter of ≈500 nm, with a hole in the middle) are prepared successfully. During the hydrothermal process, the VO2 nanoplate undergoes an interesting Ostwald ripening guided dissolution‐regrowth process, resulting in the formation of the unusual ancient Chinese coin structure. Impressively, based on structural merits of the abundant electrolyte‐accessible sites and transfer pathways, the mass transfer can be enhanced at the surface of as‐prepared VO2 nanoplates‐based electrode. The VO2 nanoplates further deliver high reversible specific capacity and rate ability for rechargeable ZIBs. Hence, this work presents a new avenue for designing unique nanostructure vanadium oxides to boost the electrochemical properties of aqueous ZIBs.

The development of strategies for tuning the electronic structure of the metal sites in single-atom catalysts (SACs) is the key to optimizing their activity. Herein, we report that iodine doping within the carbon matrix of a cobalt–nitrogen–carbon (Co–N–C) catalyst can effectively modulate its electronic structure and catalytic activity toward the hydrogen evolution reaction (HER). The iodine-doped Co–N–C catalyst shows exceptional HER activity in acid with an overpotential of merely 52 mV at 10 mA cm–2, a small Tafel slope of 56.1 mV dec–1, making it among the best SACs based on both precious and nonprecious metals. Moreover, this catalyst possesses a high turnover frequency (TOF) value of 1.88 s–1 (η = 100 mV), which is about 1 order of magnitude larger than that (0.2 s–1) of the iodine-free counterpart. Experimental and theoretical studies demonstrate that the introduction of iodine dopants lowers the chemical oxidation state of the Co sites, resulting in the optimized hydrogen adsorption and facilitated HER kinetics. This work provides an alternative strategy to regulate the electronic structure of SACs for improved performance.

Single-atom catalysts (SACs) hold great promise for highly efficient heterogeneous catalysis, yet the practical applications require the development of highdensity active sites with flexible geometric structures. The lack of understanding in the dynamic formation process of single atoms in the host framework has been plaguing the controllable synthesis of next generation SACs. Here using Co-based metal-organic frameworks (MOFs) as a starting substrate, we fully elucidated the formation of high-density Pt single atoms with inter-site interactions in derived Co 3 O 4 host. The cation exchange process and dynamic evolution of PtÀ Pt interactions, organic ligand cleavage and Pt-oxygen coordination formation during the pyrolysis process have been unambiguously interpreted by a series of in situ/ex situ spectroscopic measurements and theoretical computation. These findings would direct the synthesis of highdensity SACs with metal-metal interactions, which demonstrate significantly enhanced structural flexibility and catalytic properties.

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