The application of anion exchange membrane fuel cells is hampered by the development of highly efficient and earth-abundant anode hydrogen oxidation reaction (HOR) catalysts. Here, a series of nickel catalysts (denoted as Ni-X) with different lattice oxygen (LO) contents were synthesized by H2 reduction of nickel hydroxide at temperatures (X) ranging from 300 to 500 °C. The Ni-400 (LO/Ni = 0.41, NiO0.41) catalyst with an optimum LO content showed excellent HOR activity and stability, comparable to current Ni-based electrocatalysts. An X-ray photoemission spectroscopic study, combined with density functional theory calculations, suggested that introducing LO into Ni modified the metal d-band electronic structure and in turn the hydrogen binding energy, which played a major role in determining the HOR performance.
Rational modulation of co-catalyst properties through strategic metal doping and structural engineering emerges a promising approach to simultaneously tackle critical challenges in photocatalytic hydrogen evolution—specifically, suppressing photogenerated carrier recombination and optimizing hydrogen adsorption thermodynamics. This work demonstrates the synergistic integration of manganese doping and amorphous core-shell architecture in a bimetallic sulfide co-catalyst (Mn-CoS x ), designed to overcome the inherent limitations of conventional crystalline CoS systems. The developed Mn-CoS x features a homogeneous nanostructure with an enlarged specific surface area (SSA ≈ 112.46 m 2 g −1 ) and abundant exposed sulfur active sites, while Mn incorporation effectively reduces the hydrogen adsorption free energy (ΔG H∗ = −0.51 eV) through d-band electronic structure modulation. When coupled with CdS photocatalysts, the optimized Mn-CoS x /CdS composite achieves exceptional hydrogen evolution rates of 19.1 mmol g −1 h −1 under visible light irradiation, representing 9-fold enhancement over benchmark CoS/CdS, 112-fold over bare CdS, and 21-fold over Pt/CdS systems, respectively. Notably, the amorphous core-shell configuration not only facilitates efficient charge separation but also enables dynamic surface reconstruction during catalytic operation. This work establishes a universal design principle for transition metal-based co-catalysts through the synergistic combination of atomic-level doping strategies and nanoscale structural engineering, providing new insights into the development of cost-effective, noble metal-free photocatalytic systems for sustainable energy conversion.
Zhiqian Hou,Chaozhu Shu,Peng Hei,Tingshuai Yang,Ruixin Zheng,Zhiqun Ran,Minglu Li,Jianping Long
The degradation of oxygen electrodes caused by oxygen species in lithium–oxygen (Li–O2) batteries deteriorates their energy efficiency and cyclability and seriously hinders their commercial application. To achieve high energy efficiency and long-term cycle life, gradient-porous ultrathin FeCo2S4 nanosheets on Ni foam (FeCo2S4@Ni) were deliberately designed as a noncarbonaceous freestanding oxygen electrode for Li–O2 batteries. Notably, the gradient-porous structure in FeCo2S4@Ni can offer sufficient active sites as well as mitigate polarization caused by the mass transfer during discharge and charge. The synergistic effect of the two transition metals, Fe2+ and Co3+, optimizes their d-band electronic structure and enhances the intrinsic activity of the oxygen electrode. Benefiting from the above merits, the FeCo2S4@Ni based Li–O2 battery demonstrates greatly increased discharge capacity (8001 mA h g−1), improved rate capability (with a high capacity of 4401 mA h g−1 at 500 mA g−1), and enhanced cycling stability (with a low overpotential of below 1 V after 109 cycles). Our work demonstrates that the battery performance can be improved by regulating the structure and composition of the oxygen electrode and provides a promising strategy for developing high performance Li–O2 batteries.
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