Atomic-level Ru-Ir mixing in rutile-type (RuIr)O2 for efficient and durable oxygen evolution catalysis

Nitrogen-doped carbon nanotube encapsulated CoCu bimetallic alloy particles to promote efficient oxygen evolution reaction via electronic structure regulation

The rational design of efficient and cost-effective transition metal alloy electrocatalysts represents a huge challenge for the oxygen evolution reaction (OER). Herein, the bimetallic CoCu-MOF is employed as a template to significantly enhance the catalytic activity through in situ pyrolysis into melamine-assisted nitrogen-doped carbon nanotube (NCNT) encapsulated metal alloy electrocatalyst (Co1Cu1@NCNT/CC). The Co1Cu1@NCNT/CC demonstrates superior OER activity in 1 M KOH. The overpotential is 263 mV at 10 mA cm-2. Meanwhile, the catalyst exhibits superior long-term stability. The experimental results and density functional theory (DFT) calculations reveal the bimetallic synergies regulate the electronic structure and strong electronic metal-support interaction (EMSI) of the catalysts, increase the electron transport efficiency and optimize the adsorption capacity of oxygen-containing intermediates, leading to a significant improvement in both the OER activity and stability.

Distribution of Oxygen Vacancies in RuO2 Catalysts and Their Roles in Activity and Stability in Acidic Oxygen Evolution Reaction

By combining density functional theory (DFT) calculations and the cluster expansion (CE) model in an active-learning framework, we comprehensively studied the distribution features of oxygen vacancies (OV's) as well as their contributions to the stability and activity of the RuO2 catalyst in acidic oxygen evolution reaction (OER). The results show that OV's prefer to be located at bridge oxygen sites on the RuO2(110) surface and the next-nearest-neighbor trans positions of surface RuO6 octahedra in pairs due to interactions between two OV's, and high concentrations of OV's exhibit a continuous zigzag distribution in the (110) plane of RuO2. The oxygen vacancy distribution can be explained by the charge repulsion between the low-valent Ru and O, which is referred to as the "heterovalent ion-oxygen exclusion principle". In addition, the DFT results show that the presence of OV's cannot improve the inherent OER activity of specific Ru sites since low-valent Ru sites hinder deprotonation of the second water molecule. Nevertheless, OV's can improve the stability of RuO2 by suppressing the lattice oxygen mechanism (LOM) path. In summary, this work provides deeper insights into the mechanism of the OER of RuO2 with OV's in acidic media and a possible way to improve catalyst performance by using oxygen vacancy engineering.

Bi-Doped NiCo2O4 Catalyst for Electrocatalysis Glucose Oxidation Accompanied Hydrogen Generation

The slow dynamics of oxygen evolution reaction and the use of the proton exchange membrane have been troubling the hydrogen production from electrolytic water splitting. Reducing the electrolytic voltage and avoiding the utilization of proton exchange membranes are crucial targets for electrolytic hydrogen evolution. Bi-doped NiCo2O4 catalyst is prepared and applied in electrocatalysis glucose oxidation coupled hydrogen generation. Structural characterizations confirm the successful preparation of NiCo2O4 and the existence of Bi. Bi leads to the electrons transfer from Co to Ni, increasing the content of Co3+, and lowers the oxidation potential of Co. Electrochemical experiments indicate that NiCo2O4-Bi has good electrocatalytic activity and stability toward electrochemical glucose oxidation, with a potential of 1.13 V vs RHE at 10 mA cm-2 current density. The asymmetric electrolysis of two electrodes requires just 1.26 V to achieve a 10 mA cm-2 current density. The design of NiCo2O4-Bi is an exploration for electrocatalytic glucose oxidation coupled hydrogen production with low voltage and no proton exchange membrane.