Theoretical Study on the High HER/OER Electrocatalytic Activities of 2D GeSi, SnSi, and SnGe Monolayers and Further Improvement by Imposing Biaxial Strain or Doping Heteroatoms

Theoretical Investigation of HER and OER Electrocatalysts Based on the 2D R-graphyne Completely Composed of Anti-Aromatic Carbon Rings

Based on the DFT calculations, two-dimensional (2D) R-graphyne has been demonstrated to have high stability and good conductivity, which can be conducive to the relevant electrocatalytic activity of the material. Different from the poor graphene, R-graphyne, which is completely composed of anti-aromatic structural units, can exhibit certain HER catalytic activity. In addition, doping the TM atoms in Group VIIIB can be considered an effective strategy to enhance the HER catalytic activity of R-graphyne. Particularly, Fe@R-graphyne, Os@R-graphyne, Rh@R-graphyne and Ir@R-graphyne can exhibit higher HER catalytic activities due to the formation of more active sites. Usually, the shorter the distance between the TM and C atoms is, the better the HER activity of the C-site is. Furthermore, doping Ni and Rh atoms of Group VIIIB can significantly improve the OER catalytic performance of R-graphyne. It can be found that ΔG_O* can be used as a good descriptor for the OER activities of TM@R-graphyne systems. Both Rh@R-graphyne and Ni@R-graphyne systems can exhibit bifunctional electrocatalytic activities for HER/OER. In addition, all the relevant catalytic mechanisms are analyzed in detail. This work not only provides nonprecious and highly efficient HER/OER electrocatalysts, but also provides new ideas for the design of carbon-based electrocatalysts.

Through the Self-Optimization process to achieve high OER activity of SAC catalysts within the framework of TMO3@G and TMO4@G: A High-Throughput theoretical study

High-throughput DFT calculations are performed to explore the oxygen evolution reaction (OER) catalytic activity of a series of 2D graphene-based systems with TMO₃ or TMO₄ functional units. By screening the 3d/4d/5d transition metal (TM) atoms, a total of twelve TMO₃@G or TMO₄@G systems had extremely low overpotential of 0.33 ∼ 0.59 V, in which the V/Nb/Ta atom in VB group and Ru/Co/Rh/Ir atom in VIII group served as the active sites. The mechanism analysis reveals that the filling of outer electrons of TM atom can play an important role in determining the overpotential value by affecting the ΔG_O* value as an effective descriptor. Especially, in addition to the general situation of OER on the clean surface of the systems containing the Rh/Ir metal centers, the self-optimization process of TM-sites was carried out, and it made most of these single-atom catalysts (SAC) systems to have high OER catalytic activity. All these fascinating findings can contribute to an in-depth understanding of the OER catalytic activity and mechanism of the excellent graphene-based SAC systems. This work will facilitate the design and implementation of non-precious and highly efficient OER catalysts in the near future.

Embedding Group VIII Elements into a 2D Rigid pc-C3N2 Monolayer to Achieve Single-Atom Catalysts with Excellent OER Activity: A DFT Theoretical Study

Under DFT calculations, a systematic investigation is carried out to explore the structures and oxygen evolution reaction (OER) catalytic activities of a series of 2D single-atom catalyst (SAC) systems, which are constructed by doping the transition metal (TM) atoms in group VIII into the cavities of rigid phthalocyanine carbide (pc-C₃N₂). We can find that when Co, Rh, Ir and Ru atoms are doped in the small or large cavities of a pc-C₃N₂ monolayer, they can be used as high-activity centers of OER. All these four new TM@C₃N₂ nanostructures can exhibit very low overpotential values in the range of 0.33~0.48 V, even smaller than the state-of-the-art IrO₂ (0.56 V), which indicates considerably high OER catalytic activity. In particular, the Rh@C₃N₂ system can show the best OER performance, given that doped Rh atoms can uniformly serve as high-OER-active centers, regardless of the size of cavity. In addition, a detailed mechanism analysis was carried out. It is found that in these doped pc-C₃N₂ systems, the number of outer electrons, the periodic number of doped TM atoms and the size of the embedded cavity can be considered the key factors affecting the OER catalytic activity, and excellent OER catalytic performance can be achieved through their effective cooperation. These fascinating findings can be advantageous for realizing low-cost and high-performance SAC catalysts for OER in the near future.

Amorphous Co-Mo-B Film: A High-Active Electrocatalyst for Hydrogen Generation in Alkaline Seawater

The development of efficient electrochemical seawater splitting catalysts for large-scale hydrogen production is of great importance. In this work, we report an amorphous Co-Mo-B film on Ni foam (Co-Mo-B/NF) via a facile one-step electrodeposition process. Such amorphous Co-Mo-B/NF possesses superior activity with a small overpotential of 199 mV at 100 mA cm-2 for a hydrogen evolution reaction in alkaline seawater. Notably, Co-Mo-B/NF also maintains excellent stability for at least 24 h under alkaline seawater electrolysis.