Computational Electrochemistry of Water Oxidation on Metal-Doped and Metal-Supported Defective h-BN

Single Ir atom anchored in pyrrolic-N4 doped graphene as a promising bifunctional electrocatalyst for the ORR/OER: a computational study

The development of highly-efficient electrocatalysts with bifunctional catalytic activity for oxygen reduction reaction (ORR) and oxygen evolution reaction. (OER) still remains a great challenge for the large-scale application of renewable energy conversion and storage technologies. Herein, by means of comprehensive density functional theory (DFT) computations, we systematically explored the potential of pyrrolic-N doped graphene (pyrrolic-N₄-G) supported various transition metal atoms (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Pd, W, Os, Ir, and Pt) as electrocatalysts for the ORR and OER. Our results revealed that these TM/pyrrolic-N₄-G candidates exhibit high electrochemical stability due to their positive dissolution potentials. Especially, the Ir/pyrrolic-N₄-G can perform as a promising bifunctional electrocatalyst for both ORR and OER with the low overpotentials (η^ORR = 0.34 V and η^OER = 0.32 V). Interestingly, multiple-level descriptors, including energy descriptor (ΔG_OH* - ΔG_O*), (ΔG_OH*), structure descriptor (φ), and d-band center (ε) can well rationalize the origin of the high catalytic activity of Ir/pyrrolic-N₄-G for the ORR/OER. Our findings not only further enrich the SACs, but also open a new avenue to develop novel 2D materials-based SACs for highly efficient oxygen electrocatalysts.

Carbon and Oxygen Coordinating Atoms Adjust Transition Metal Single-Atom Catalysts Based On Boron Nitride Monolayers for Highly Efficient CO2 Electroreduction

Although single-atom catalysts (SACs) with transition metal-nitrogen complexes have been studied widely, investigations that use light-element atoms to adjust the coordination environment of the central metal atoms in metal-nitrogen complexes are still rare but show enormous potential for various electrocatalytic reactions. Herein, we design novel SACs based on monolayer BN adjusted by B, C, or O coordinating atoms as catalysts for the CO₂ reduction reaction (CRR). These SACs are denoted as M@BN_D (BN = monolayer boron nitride; D = B, C, or O atom; M = Co, Cr, Fe, Mn, Mo, Pd, Pt, Ru, V, W, Ni, Zn, Zr, Ag, Au, Cu, or Ti atom) and are investigated as CRR catalysts using density functional theory calculations. Among these structures, we identified some promising candidate catalysts for CRR with impressive low limiting potential (U_L): Pt@BN_C with a U_L of -0.18 for the product CH₄ and Co@BN_C and Au@BN_O with U_L of -0.41 and -0.37 V, respectively, for the product CH₃OH. In particular, Pt@BN_C shows a remarkable reduction in U_L for the product CH₄ compared to any existing catalysts, synthesized or predicted. In addition, the ultralow U_L for CRR on Pt@BN_C was derived from the unique bonding feature between the single metal atom and adsorbates and the modulation of ionic interactions induced by the coordination effect of the C atom.

Rational design of the carbon doping of hexagonal boron nitride for oxygen activation and oxidative desulfurization

The doping of hexagonal boron nitride (h-BN) materials has a great influence on their catalytic oxidation performance, but the mechanism of doping has still not been studied in depth to date. Herein, carbon-doped h-BN materials were systematically investigated. Three different doping modes were established, and their performance for O₂ activation and oxidative desulfurization (ODS) were explored. DFT calculation showed that not all carbon-doped forms of the h-BN surface could activate O₂. Specifically, two of the dispersed doping forms could activate O₂, whereas the π-doping form could not activate O₂, and thus the ODS reaction could not be carried out. For the two dispersed doping forms, the O₂ adsorption on the C_B-doped h-BN surface (C-doped in B position) was too strong, which hampered its ODS performance; whereas the O₂ adsorption on the C_N-doped h-BN surface (C-doped in the N position) was moderate, resulting in good catalytic activity for ODS. Therefore, to design effective BN-based catalysts by C doping, it is suggested that the C dopant should be dispersed to substitute the N atom of h-BN, and C_N-doped h-BN will play an important role in ODS with moderate O₂ activation. This study can be used as a reference for the catalytic oxidation of boron nitride.