High-Valence Mo Doping and Oxygen Vacancy Engineering to Promote Morphological Evolution and Oxygen Evolution Reaction Activity

Synergistic regulation of d-band center photocatalytic hydrogen evolution at S-scheme heterojunction reduction sites through defect engineering and interface electric field

The efficiency of photocatalytic hydrogen evolution can be significantly enhanced while maintaining cost-effectiveness through the synergistic effect of defect surface engineering and multi-component heterojunctions. The structure and properties of NiCo2O4 nanorods were modified by inducing oxygen vacancies at different temperatures in this study, resulting in improved optical properties and electron adsorption capacity. The presence of oxygen vacancies leads to a reduction in the band gap of NiCo2O4, thereby enhancing electron transport efficiency through band gap engineering. Simultaneously, surface properties undergo changes, and vacancy defects serve as electron trapping centers, facilitating an increased participation of electrons in the hydrogen evolution reaction process. The dodecahedron KMP with a cavity structure is additionally introduced to form an S-scheme heterojunction with NiCo2O4. This establishes a novel mechanism for electron transport, which effectively enhances the separation of electron-hole pairs and improves the redox capacity of the photocatalytic system. The adsorption of intermediates in the hydrogen production process is enhanced through synergistic regulation of d-band centers via surface defect engineering and S-scheme heterojunction. Additionally, this approach improves the separation efficiency of electron-hole pairs and accelerates electron transfer dynamics, significantly enhancing hydrogen production efficiency.

Mo-Doped Mesoporous RuO2 Spheres as High-Performance Acidic Oxygen Evolution Reaction Electrocatalyst

The development of highly active and acid-stable electrocatalysts for oxygen evolution reaction (OER) is of great significance for water electrolysis technology. Herein, a highly efficient molybdenum-doped mesoporous ruthenium dioxide sphere (Mo-RuO2 ) catalyst is fabricated by a facile impregnation and post-calcination method using mesoporous carbon spheres to template the mesostructure. The optimal Mo0.15 -RuO2 catalyst with Mo doping amount of 15 mol.% exhibits a significantly low overpotential of 147 mV at 10 mA cm-2 , a small Tafel slope of 38 mV decade-1 , and enhanced electrochemical stability in acidic electrolyte, far superior to the commercial RuO2 catalyst. The experimental results and theoretical analysis reveal that the remarkable electrocatalytic performance can be attributed to the large surface area of the mesoporous spherical structure, the structural robustness of the interconnected mesoporous framework, and the change in the electronic structure of Ru active sites induced by Mo doping. These excellent advantages make Mo-doped mesoporous RuO2 spheres a promising catalyst for highly efficient electrocatalytic OER in acidic media.

Opposite Electron Transfer Induced High Valence Mo Sites for Boosting the Water Splitting Performance of Ir Atoms

Developing highly efficient and low-cost bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting poses significant challenges. In this study, a novel bifunctional electrocatalyst, Irn-CoMoPOx, was achieved via incorporating low-loading Ir single atoms and clusters with the high-valence Mo6+ modified CoPOx nanosheets. The Irn-CoMoPOx catalyst demonstrates remarkable low overpotentials of 222 mV and 36 mV for the OER and HER, respectively, in delivering a current density of 10 mA cm-2. When employed as both the anode and cathode catalyst in overall water splitting, the Irn-CoMoPOx∥Irn-CoMoPOx configuration exhibits a superior cell voltage of 1.53 V, outperforming the benchmark Pt/C∥IrO2 electrolytic cell (1.60 V) for achieving the current density of 10 mA cm-2. Benefiting from the high-valence of Mo species, the metal-support interaction of Irn-CoMoPOx was greatly strengthened, resulting in an order of magnitude increase in the mass activity of Ir for the HER. The high valence of non-noble metals plays a crucial role in tuning the local electronic configurations and optimizing the adsorption energies of the intermediates, which synergistically improves the overall performance of Ir in water splitting. The study provides valuable insights for future research in the utilization of Ir-based bifunctional catalysts for overall water electrocatalysis applications.