The electronic metal–support interaction (EMSI) plays a crucial role in catalysis as it can induce electron transfer between metal and support, modulate the electronic state of the supported metal, and optimize the reduction of intermediate species. In this work, the tailoring of electronic structure of Pt single atoms supported on N‐doped mesoporous hollow carbon spheres (Pt1/NMHCS) via strong EMSI engineering is reported. The Pt1/NMHCS composite is much more active and stable than the nanoparticle (PtNP) counterpart and commercial 20 wt% Pt/C for catalyzing the electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 40 mV at a current density of 10 mA cm−2, a high mass activity of 2.07 A mg−1Pt at 50 mV overpotential, a large turnover frequency of 20.18 s−1 at 300 mV overpotential, and outstanding durability in acidic electrolyte. Detailed spectroscopic characterizations and theoretical simulations reveal that the strong EMSI effect in a unique N1−Pt1−C2 coordination structure significantly tailors the electronic structure of Pt 5d states, resulting in promoted reduction of adsorbed proton, facilitated H−H coupling, and thus Pt‐like HER activity. This work provides a constructive route for precisely designing single‐Pt‐atom‐based robust electrocatalysts with high HER activity and durability.

Water-electrolysis technology can realize zero CO 2 emission and acquire large-scale hydrogen with high purity (>99.9%), and thus potentially serves as a key component in future sustainable energy systems. [1,2] However, this technology accounts for only 4% of current hydrogen production, which is mainly attributed to its higher cost in comparison with other methods such as the conversion of natural fossil fuels. [3] For commercial water electrolysis systems, the existing key problems mainly focus on the use of efficient but exorbitant iridium, ruthenium or platinum catalysts, or economically practical nickel meshes and stainless steel with the unsatisfying activity. [4] Exploring highly active and costeffective catalysts with good durability is imperative but challenging. Though important breakthroughs have been made recently in investigating high-efficiency first-row transition metal catalysts for oxygen and hydrogen evolution reactions (OER and HER), [5-9] a certain gap still exists between the test condition (almost at room temperature, Table S1, Supporting Information) and the industrial one (at 50-80 °C). Therefore, it is essential to evaluate the catalytic performance and compatibility of catalysts under such harsh operating condition for further practical applications. Rational design of HER and OER catalysts which can be well operated at industrial temperatures is highly desirable for practical alkaline water electrolysis (AWE) application. Our reported MoO 2-Ni arrays exhibited a Pt-like HER activity at 25.0 °C, and the convenient synthesis route was beneficial to its mass production. [10] Such a catalyst serves as a potential candidate because its heterogeneous components may avoid agglomeration under high-temperature catalytic conditions. For anodic OER, some researchers recently evaluated the catalytic performance at 80 °C, such as NiFe-LDH [11] in alkali or CoFePbO x [12] in acid, however with only ≈20 h operation. Our recent works have focused on the reconstruction chemistry of catalysts, demonstrating that the deeply/completely reconstructed (denoted as DR/CR) catalysts are a potential choice. The reported DR-NiOOH was operated well with activity decay of 0.35 mV h −1 in 40 h tested at 52.8 °C. [13] In addition, the DR catalysts with abundant active species can realize high component utilization and thus high-mass-activity catalysis. Nevertheless, the lithiation Evaluating the alkaline water electrolysis (AWE) at 50-80 °C required in industry can veritably promote practical applications. Here, the thermally induced complete reconstruction (TICR) of molybdate oxygen evolution reaction (OER) pre-catalysts at 51.9 °C and its fundamental mechanism are uncovered. The dynamic reconstruction processes, the real active species, and stereoscopic structural characteristics are identified by in situ low-/ high-temperature Raman, ex situ microscopy, and electron tomography. The completely reconstructed (CR) catalyst (denoted as cat.-51.9) is interconnected by thermodynamically stable (oxy)hydroxide nanopartic...

The mechanism of Ti3C2-MXene ambient oxidation has been revealed by electron microscopy, disclosing the effects of defects and Ti-ion diffusion.

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The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally attributed to the phase transitions from the layered structure to spinel and rocksalt structures that contain less lattice oxygen. Here, a different degradation pathway in LiCoO2 is found, through oxygen vacancy facilitated cation migration and reduction. This process leaves undercoordinated oxygen that gives rise to oxygen release while the structure integrity of the defect-free region is mostly preserved. This oxygen release mechanism can be called surface degradation due to the kinetic control of the cation migration but has a slow surface to bulk propagation with continuous loss of the surface cation ions. It is also strongly correlated with the high-voltage cycling defects that end up with a significant local oxygen release at low temperatures. This work unveils the thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach.