MoS2 with 2D structure shows efficient hydrogen evolution reaction (HER) performance because undercoordinated Mo–S edges have ideal hydrogen adsorption free energy. MoS2 usually does not satisfy the bifunctional catalysts because of the poor intrinsic oxygen evolution reaction (OER) catalytic activity. Herein, it is proposed to construct heterostructure with OER active components to induce efficient bifunctional catalytic activity along with heteroatom doping to modify the electronic structure to optimize the adsorption and desorption capabilities of reaction intermediates. La‐doped Ni3S2/MoS2 grown on nickel foam (La‐NMS@NF) is synthesized as bifunctional catalyst taking advantage of the excellent OER performance of Ni3S2. La‐NMS@NF evolves into nanoflower‐like structures with the addition of La dopant, which provides abundant pore channels to facilitate mass transfer and exposure of active sites. Density functional calculations reveal that the La‐doped Ni3S2/MoS2 heterointerface can optimize the water adsorption and H* adsorption/desorption, improving the HER performance. The La‐NMS@NF exhibits an overpotential of 154 and 300 mV for HER and OER at 100 mA cm−2 in 1.0 m KOH. Herein, a heteroatom‐driven heterostructure activation strategy for electron rearrangement and structural evolution in electrocatalysts to decrease energy consumption in overall water splitting is demonstrated.
The surface structures, bond variations, and segregation of oxygen vacancies play crucial roles in the structural stability and functionality of nanocrystalline rare‐earth zirconate pyrochlores. In this work, the stabilities of (1 0 0), (1 1 0), and (1 1 1) surfaces of pyrochlore A2Zr2O7 (A = La, Ce, Pr, Nd, Pm, Sm, Eu, or Gd) are investigated by first‐principles calculations. Surface reconstruction occurs on (1 1 0) surface with a transition of ZrO6 octahedron to ZrO4 tetrahedron, leading to their large relaxation energies. In combination with the small amount of broken bonds during the surface formation process, the (1 1 0) surfaces are identified having the lowest surface formation energies than the (1 0 0) and (1 1 1) surfaces. Moreover, the reconstructed (1 1 0) surface has characteristics of the segregation of oxygen vacancies. The surface oxygen vacancies have the low migration barriers (<1.2 eV), which are comparable with those in bulk and ensure the long‐distance diffusion of oxygen vacancies in A2Zr2O7. These discoveries provide fundamental insight to the surface structure and related oxygen vacancy behavior, which are expected to guide the optimization of the surface related properties for nanocrystalline rare‐earth zirconates.
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