Theoretical Basis of Electrocatalysis

In this chapter, we introduce the density functional theory (DFT)-based computational approaches to the study of various electrochemical reactions (hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR)) occurring on heterogeneous catalysis surfaces. A detailed computational approach to the theoretical interpretation of electrochemical reactions and structure-catalytic activity relationships for graphene-based catalysts will be discussed. The electrocatalytic activity of catalysis can be theoretically evaluated by overpotential value determined from free energy diagram (FED) of electrochemical reactions. By comparing electrocatalytic activity of systematically designed graphene-based catalysts, we will discuss the structure-catalytic activity relationships, especially the electronic and geometrical effects of heteroatom dopants

Type I interferon is critical for the homeostasis and functional maturation of type 3 γδ T cells

Iridium­(III) cyclometalates (<b>1c</b> and <b>2c</b>) in which the two carborane units on the 4- or 5-positions of 2-phenylpyridine (ppy) ligands were tethered by an alkylene linker were prepared to investigate the effect of free rotation of <i>o</i>-carborane on phosphorescence efficiency. In comparison with the unlinked complex, tethering the <i>o</i>-carboranes to the 5-positions of ppy ligands (<b>2c</b>) enhanced phosphorescence efficiency by over 30-fold in polar medium (Φ_PL = 0.37 vs 0.011 in THF), while restricting the rotation of <i>o</i>-carborane at the 4-positions (<b>1c</b>) negatively affected the phosphorescence efficiency. The different effects of restricted rotation of <i>o</i>-carborane on phosphorescence efficiency were likely a result of the different variations of the carboranyl C–C bond distances in the excited state

A robust nonprecious CuFe composite as a highly efficient bifunctional catalyst for overall electrochemical water splitting

To generate hydrogen, which is a clean energy carrier, a combination of electrolysis and renewable energy sources is desirable. In particular, for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in electrolysis, it is necessary to develop nonprecious, efficient, and durable catalysts. A robust nonprecious copper–iron (CuFe) bimetallic composite is reported that can be used as a highly efficient bifunctional catalyst for overall water splitting in an alkaline medium. The catalyst exhibits outstanding OER and HER activity, and very low OER and HER overpotentials (218 and 158 mV, respectively) are necessary to attain a current density of 10 mA cm−2. When used in a two‐electrode water electrolyzer system for overall water splitting, it not only achieves high durability (even at a very high current density of 100 mA cm−2) but also reduces the potential required to split water into oxygen and hydrogen at 10 mA cm−2 to 1.64 V for 100 h of continuous operation

Aromatic cages B: unprecedented existence of octagonal holes in boron clusters

The cage-like structures containing octagonal holes are located as the lowest-lying isomers for the B. The presence of octagonal holes, which have been found for the first time, not only gives us new insight into the bonding motif, but also marks a breakthrough in the structural characteristics of boron clusters since they were never expected to be stable units for elemental clusters. These cages are composed of both delocalized σ and π electron systems that consequently make them aromatic and thermodynamically stable.status: publishe

<i>p</i>- and <i>n</i>‑type Doping Effects on the Electrical and Ionic Conductivities of Li₄Ti₅O₁₂ Anode Materials

We systematically investigated p- and n-type doping effects on the electrical conductivity of spinel Li₄Ti₅O₁₂ (LTO) by designing theoretically stoichiometric Li₁₁Ti₁₃O₃₂ (p-type) and Li₁₀Ti₁₄O₃₂ (n-type) because LTO has a nonstoichiometric (Li)₈[Li_8/3Ti_40/3]­O₃₂ formula with the <i>Fd</i>3<i>m̅</i> space group. In this work, we present evidence that the electronic modification plays a fundamental role in the electrical conductivity of LTO, especially, n-type Li₁₀Ti₁₄O₃₂, which has superior electrical conductivity compared to p-type Li₁₁Ti₁₃O₃₂. We proposed a way to improve the electrical conductivity of pristine LTO by halogen ion doping, Li₄Ti₅O_{12–<i>x</i>}Hal_<i>x</i> (Hal: F, Cl, and Br), for an n-type doping effect. However, the substitution of halogen ions can enhance the electrical conductivity by mixing Ti⁴⁺/Ti³⁺ and impede the Li ion diffusion in the lattice. The larger size of Cl and Br increases the Li ion diffusion energy barrier with van der Waals repulsion. Therefore, our theoretical investigations of the effects of halogen doping on the electrical and ionic conductivities anticipate that the smaller-sized F may be the most promising dopant for improving the performance of LTO

<i>o</i>‑Carboranyl–Phosphine as a New Class of Strong-Field Ancillary Ligand in Cyclometalated Iridium(III) Complexes: Toward Blue Phosphorescence

Heteroleptic tris-cyclometalated Ir­(III) complexes supported by the <i>o</i>-carboranyl–phosphine ligand (<i>CBP</i>), (C^∧N)₂Ir­(<i>CBP</i>) (C^∧N = <i>ppy</i> (<b>1</b>), <i>dfppy</i> (<b>2</b>)), have been synthesized and characterized. The PL spectra of <b>1</b> and <b>2</b> displayed substantially blue shifted phosphorescence relative to the corresponding Ir­(C^∧N)₃ complexes. Electrochemical and theoretical studies showed that the <i>CBP</i> ligand functioned as a strong-field ancillary ligand, and the greater HOMO stabilization in comparison to that of the LUMO by the <i>CBP</i> ligand was responsible for the increase in band gap, leading to a large blue shift in phosphorescence