A series of tetragonal zirconia-supported CuO oxide catalysts with various CuO loadings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), ultraviolet and visible diffuse reflectance spectroscopy (UV/vis-DRS), and temperature-programmed reduction (TPR) measurements. The results indicate that the dispersion capacity of copper oxide on this support is approximately 8.6 Cu(2+) ions/nm(2) ZrO(2). The state of the resulting supported copper species depends on the CuO loading. At CuO loadings below the dispersion capacity, only highly dispersed copper ion species are present on the surface of t-ZrO(2). In particular, isolated Cu ions are the predominant species at low loadings. In contrast, pair Cu ions become the most abundant species at loadings near the dispersion capacity. It has been proposed that these dispersed CuO (isolated and paired Cu ions) have a symmetric 5-fold-oxygen-coordination symmetry (C(3)(v) symmetry) and can be described as distorted octahedra with a missing corner or a trigonal bipyramids. Finally, at CuO loadings above the dispersion capacity the formation of crystalline CuO is observed. TPR results reveal that the dispersed Cu ion species have a different reducibility from CuO crystallites, presumably due to strong interactions between these species and the t-ZrO(2) support. The catalytic activity of these CuO/t-ZrO(2) catalysts for the decomposition of N(2)O can also be directly correlated to CuO dispersion, with paired Cu ions being the most active species for this reaction.

due to the largely increased number of active sites and more effective dangling bonds/defects. Despites these flashing points, the poor crystallinity and defective structure in amorphous materials often lead to the high solubility and low stability in aqueous solution, [7] and thus limit the practical utilization of amorphous catalysts. Therefore, it is needed to develop efficient strategies to stabilize amorphous catalysts.Molybdenum oxysulfide (MoS x O y ) as a potential hydrogen evolution reaction (HER) catalyst overcomes the in-plane inertness and low conductivity of molybdenum disulfide due to the highly active Mo-oxo and metallic nature of molybdenum oxides. [7,8] However, amorphization induces obvious degradation of stability in oxygen-containing molybdenum compounds due to their high solubility in aqueous electrolyte to form molybdic acid. [9] Two strategies are employed to solve this critical issue: one is to coat a thin layer of catalysts to a substrate (e.g., graphene) with the bridging group to strengthen the interaction between catalysts and substrate; [10] the other method is to convert unstable phases/structures to aqueous solution-resistant ones. [11] Although these attempts can enhance the stability to a certain extent, a balanced strategy to simultaneously maintain the active species/structure and enhance the stability remains not yet achieved. Amorphization is an efficient strategy to activate intrinsically inert catalysts. However, the low crystallinity of amorphous catalysts often causes highsolubility and poor electrochemical stability in aqueous solution. Here, a different mechanism is developed to simultaneously stabilize and activate the water-soluble amorphous MoS x O y via a charge-balancing strategy, which is induced by different electronegativity between the co-dopants Rh (2.28) and Sn (1.96). The electron-rich Sn prefers to stabilize the unstable apical O sites in MoS x O y through charge transfer, which can prevent the H from attacking. Meanwhile, the Rh, as the charge regulator, shifts the main active sites on the basal plane from inert Sn to active apical Rh sites. As a result, the amorphous RhSn-MoS x O y exhibits drastic enhancement in electrochemical stability (η 10 increases only by 12 mV) after 1000 cycles and a distinct activity (η 10 : 26 mV and Tafel: 30.8 mV dec −1 ) for the hydrogen evolution reaction in acidic solution. This work paves a route for turning impracticably water-soluble catalysts into treasure and inspires new ideas to design high-performance amorphous electrocatalysts.

Fabrication of advanced electrocatalysts acting as an electrode for simultaneous hydrogen and oxygen evolution reactions (i.e., HER and OER) in an overall cell has attracted massive attention but still faces enormous challenges. This study reports a significant strategy for the rapid synthesis of high-entropy alloys (HEAs) by pulsed laser irradiation. Two types of intrinsic atomic hollow sites over the surface of HEAs are revealed that enable engaging bifunctional activities for water splitting. In this work, a novel senary HEA electrocatalyst made of FeCoNiCuPtIr facilitates the redox of water at only 1.51 V to achieve 10 mA cm −2 and still remains steadily catalytic and durable after being subjected to a 1m KOH solution for more than 20 h. First-principles calculations reveal that the incorporation of Ir and Pt atoms with neighboring elements donate valence electrons to hollow sites weakening the coupling strength between adsorbate and alloy surface and, consequently accelerating both HER and OER. This work delivers a powerful technique to synthesize highly efficient HEA catalysts and unravels the formation mechanism of active sites across the surface of HEA catalysts.

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