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To harness the full potential of electrochemical water splitting for hydrogen and oxygen production, recent efforts have focused on the development of single atom catalysts (SACs) to enhance electrocatalytic performance while maximizing metal atom utilization. In this context, we have designed and assessed the feasibility of late first-row transition metal (TM) linked 1-Azahomocubane dimer as SACs for facilitating the water splitting reaction. The effectiveness of these designed electrocatalysts has been thoroughly evaluated through density functional theory (DFT) calculations. Remarkably, the Fe containing SAC demonstrated exceptional activity towards the hydrogen evolution reaction (HER) (ΔG H = −0.06), indicating the ability of Fe metal to facilitate the adsorption of hydrogen ions and their release as hydrogen gas. Furthermore, the Fe containing SAC revealed high stability and sufficient conductivity. This investigation underscores the potential utility of the Fe containing SAC as effective precious-metal free electrocatalysts for the HER. [Display omitted] • TM linked 1-Azahomocubane dimer SAC for water the splitting reactions. • Fe@2Cubane revealed ultra-high catalytic activity toward the HER. • The Fe based SACs serves as precious-metal free, chemically stable, and sufficiently conductive SACs. [ABSTRACT FROM AUTHOR]

In the pursuit of efficient hydrogen and oxygen production via water electrolysis, the deployment of single atom catalysts (SACs) plays a pivotal role in reducing the overpotential of this process on a large scale. Hence, the quest for suitable support materials remains imperative for the design of superior SACs. In this study, we explored the potential of the recently proposed penta-belt structure as a support matrix for anchoring late first-row transition metals (Fe - Zn). The catalytic prowess of these engineered SACs in facilitating water electrolysis is assessed through density functional theory (DFT) calculations. Remarkably, the Cu@Penta-belt SACs exhibits the highest catalytic activity for the hydrogen evolution reaction (HER), with a remarkably low ΔG H value of 0.17 eV. Additionally, Ni@Penta-belt demonstrates a competitively moderate overpotential of 0.72 V for the oxygen evolution reaction (OER). To deepen our comprehension of the bonding interactions between the metal atoms and the support structure, we introduce and apply a systematic approach for identifying and analyzing the primary binding molecular orbital. This innovative methodology can be extended to diverse doping investigations that necessitate non-periodic DFT calculations. [Display omitted] • Application of TM doped Penta-belt for the water splitting reaction. • A new method to identify and analyze the binding MOs for non-periodic systems. • Great catalytic potential towards the HER and OER of TM@Penta-belt. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable clean energy sources, the hydrogen evolution reaction (HER) has attained significant interest from the scientific community. Single-atom catalysts (SACs) are among the most promising candidates for future electrocatalysis because they possess high thermal stability, effective electrical conductivity, and excellent percentage atom utilization. In the present study, the applicability of late first-row transition metals (Fe-Zn) decorated on the magnesium oxide nanocage (TM@Mg 12 O 12 ) as SACs for the HER has been studied, via density functional theory. The late first-row transition metals have been chosen as they have high abundance and are relatively low-cost. Among the studied systems, results show that the Fe@Mg 12 O 12 SAC is the best candidate for catalyzing the HER reaction as it exhibits the lowest activation barrier for HER. Moreover, Fe@Mg 12 O 12 shows high stability ( E int = -1.64 eV), which is essential in designing SACs to prevent aggregation of the metal. Furthermore, the results of the electronic properties' analysis showed that the HOMO-LUMO gap of the nanocage is decreased significantly upon doping of Fe (from 4.81 to 2.28 eV), indicating an increase in the conductivity of the system. This study highlights the potential application of the TM@nanocage SAC systems as effective HER catalysts., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)