Single-Atom Catalysts for H2O2 Electrosynthesis via Two-Electron Oxygen Reduction Reaction

Oxygen reduction reaction via the two-electron route (2e⁻ ORR) provides a green method for the direct production of hydrogen peroxide (H₂O₂) along with in situ utilization. The effective catalysts with high ORR activity, 2e⁻ selectivity, and stability are essential for the application of this technology. Single-atom catalysts (SACs) have attracted intensively attention for H₂O₂ electrosynthesis owing to the unique geometric and electronic configurations. In this review, the mechanism and theoretical predictions for 2e⁻ ORR over SACs are first introduced. Then, the recent advances of various SACs for the electrosynthesis of H₂O₂ are documented. And the correlation between the central atom, coordination atoms, and coordination environment of SACs and the corresponding electrocatalytic ORR performance including activity, selectivity, and stability are emphatically analyzed and summarized. Finally, the major challenges and opportunities regarding the future design of SACs for the H₂O₂ production are pointed out.     

Equiatomic binary phases of Copper-Rare Earth Elements. An overview of monocuprides from first-principles calculations

Equiatomic binary phases of copper with rare earth (RE) elements exhibit either primitive cubic ( ) or orthorhombic (Pnma) structures and in some cases both. By using density functional theory (DFT), we calculated the enthalpies of formation along the series of RE elements combined equimolarly with copper. For RE from Sc to Lu, the calculated enthalpies of formation fall in the range −49.8 kJ/mol for LuCu to −9.1 kJ/mol for the least thermodynamically stable CeCu. Except NdCu, all the other cubic or orthorhombic compounds exhibit lattice stability. Either forms of NdCu indicated lattice instability. Along the Sc-group, the hypothetical primitive cubic and orthorhombic forms of LuCu are found thermodynamically and mechanically stable. The overall trend of the formation enthalpies as a function of the Meyer Periodic Number is consistent with the energy trend of the 4 f-orbital filling as moving from Sc to Lu monocuprides. In addition, the calculated Gibbs free energies indicate that the thermodynamic stability is largely due to the entropic contributions. All standard DFT calculations were also repeated with DFT+U to better describe the correlation between the 5d–4f and 3d shells of RECu compounds. It has been found that DFT+U slightly affects the enthalpies of formation of RECu binaries. Moreover, DFT+U shifts up the f-band energies of RECu with light RE elements (such as La, Ce and Pr) and in contrast lowers them in the case of RECu with heavy RE elements from Nd to Lu.     

Ni Single Atoms on Hollow Nanosheet Assembled Carbon Flowers Optimizing Polysulfides Conversion for Li−S Batteries

The sluggish conversion kinetics and shuttling behavior of lithium polysulfides (LiPSs) seriously deteriorate the practical application of lithium–sulfur (Li–S) batteries. Herein, Ni single atoms on hollow carbon nanosheet-assembled flowers (Ni-NC) are synthesized via a facile pyrolysis-adsorption process to address these challenges. The as-designed Ni-NC with enhanced mesoporosity and accessible surface area can expose more catalytic sites and facilitate electron/ion transfer. These advantages enable the Ni-NC-modified separator to exhibit both enhanced confinement-catalysis ability and suppressed shuttling of LiPSs. Consequently, the Li−S battery with Ni-NC-modified separator shows an initial capacity of 1167 mAh g⁻¹ with a low capacity decay ratio (0.033% per cycle) over 700 cycles at 1 C. Even at the sulfur loading of 6.17 mg cm⁻², a high areal capacity of 5.17 mAh cm⁻² is realized at 0.1 C, together with superior cycling stability over 300 cycles. This work provides a facile catalyst design strategy for the development of high-performance Li−S batteries.