Transition metal oxides or (oxy)hydroxides have been intensively investigated as promising electrocatalysts for energy and environmental applications. Oxygen in the lattice was reported recently to actively participate in surface reactions. Herein, we report a sacrificial template-directed approach to synthesize Mo-doped NiFe (oxy)hydroxide with modulated oxygen activity as an enhanced electrocatalyst towards oxygen evolution reaction (OER). The obtained MoNiFe (oxy)hydroxide displays a high mass activity of 1910 A/g_metal at the overpotential of 300 mV. The combination of density functional theory calculations and advanced spectroscopy techniques suggests that the Mo dopant upshifts the O 2p band and weakens the metal-oxygen bond of NiFe (oxy)hydroxide, facilitating oxygen vacancy formation and shifting the reaction pathway for OER. Our results provide critical insights into the role of lattice oxygen in determining the activity of (oxy)hydroxides and demonstrate tuning oxygen activity as a promising approach for constructing highly active electrocatalysts.

Multielement solid solution alloys are intrinsically disordered on the atomic scale, and many of their advanced properties originate from the local structural characteristics. The local structure of a NiCoCr solid solution alloy is measured with x-ray or neutron total scattering and extended x-ray absorption fine structure (EXAFS) techniques. The atomic pair distribution function analysis does not exhibit an observable structural distortion. However, an EXAFS analysis suggests that the Cr atoms are favorably bonded with Ni and Co in the solid solution alloys. This short-range order (SRO) may make an important contribution to the low values of the electrical and thermal conductivities of the Cr-alloyed solid solutions. In addition, an EXAFS analysis of Ni ion irradiated samples reveals that the degree of SRO in NiCoCr alloys is enhanced after irradiation.

The capacity and stability of the constituent electrodes critically determine the performance of Li-ion batteries (LIBs). In this study, density functional theory is employed to explore the potential application of the recently synthesized two dimensional phosphorene as an electrode material in LIBs. Our results show that Li atoms can bind strongly with the phosphorene monolayer and double layer with significant electron transfer. Besides, the structure of phosphorene is not influenced much by lithiation and the volume change is only 0.2%. After lithiation, a semiconductor-to-conductor transition is observed. The diffusion barrier values of Li are calculated to be 0.76 and 0.72 eV on monolayer and double layer phosphorene, respectively. We further demonstrate that the theoretical specific capacity of the phosphorene monolayer is 432.79 mA h g⁻¹, which is larger than those of other commercial anode materials. The influence of Si and S implantation is also examined and our results indicate that Si-doped phosphorene greatly improves the binding of Li atoms, while the diffusion barrier is not affected. Our findings show that the high capacity, low open circuit voltage, small volume change and electrical conductivity of lithiated phosphorene make it a good candidate for application as an electrode material in batteries.

The distribution of migration energies of vacancies and interstitials in Ni _0.5 Fe _0.5 has a region of overlap, an indication of their comparable mobility compared to pure Ni (indicated by dotted line), which will greatly facilitate the recombination of Frenkel pairs.