Bimetal zeolite imidazolate framework derived Mo0.84Ni0.16-Mo2C@NC nanosphere for overall water splitting in alkaline solution

Non-carbonization annealing toward regulation of cobalt-based organic-inorganic hybrids as advanced electrocatalysts for water splitting

High-temperature carbonization typically used in the preparation of advanced electrocatalysts poses significant challenges in preserving abundant functional groups essential for reactant adsorption and component stabilization. To address this, a solvothermal synthesis followed by non-carbonization annealing approach is proposed to fabricate a series of cobalt-based organic-inorganic hybrids derived from cobalt-based glycerate nanospheres (GNs). Notably, annealing in phosphorous and inert atmospheres preserves the solid nanospherical structure, whereas treatment in sulfur-rich environments results in the formation of hollowed nanospheres. Among these hybrids, phosphorized solid cobalt GNs (Co-P-GNs) exhibit the highest catalytic activity for hydrogen evolution reaction (HER), achieving a low overpotential of 152 mV at 10 mA cm-2. Meanwhile, sulfurized hollow cobalt-iron GNs (Co-Fe-S-HGNs) demonstrate good performance in catalyzing oxygen evolution reaction (OER), with a low overpotential of 273 mV at 10 mA cm-2. Both catalysts exhibit robust stability and maintain 100 % Faradaic efficiency during operation in electrolyzers for water splitting. The high performance not only stems from the well-dispersed phosphide and sulfide crystallites, offering ample catalytic active sites; but also benefits from the partially thermolyzed organic matrix enriched with heteroatoms and functional groups, which facilitates ion adsorption to initiate the reactions and tightly clenches loaded components to stabilize the active species.

Process of metal-organic framework (MOF)/covalent-organic framework (COF) hybrids-based derivatives and their applications on energy transfer and storage

The fossil-fuel shortage and severe environmental issues have posed ever-increasing demands on clean and renewable energy sources, for which the exploration of electrocatalysts has been a big challenge toward energy transfer and storage. Some indispensable features of electrocatalysts, such as large surface area, controlled structure, high porosity, and effective functionalization, have been proved to be critical for the improvement of electrocatalytic activities. Recently, the rapid expansion of metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and porous-organic polymers has provided extensive opportunities for the development of various electrocatalysts. Moreover, combining diverse descriptions of porous-organic frameworks (such as MOFs and COFs) can generate amazing and fantastic properties, affording the formed MOF/COF (including core-shell MOF@MOF and MOF@COF and layer-on-layer MOF-on-MOF or COF-on-MOF) heterostructures wide applications in diverse fields, especially in clean energy and energy transfer. To further boosts electronic conductivity, catalytic performances, and energy storage abilities, these MOF/COF hybrid materials have been widely utilized as versatile precursors for the manufacture of transition metal catalysts embedded within mesoporous carbon nitrides (M@CN_x) and porous carbon nitride frameworks (CN_x) via a facile pyrolysis process. Given that these M@CN_x and CN_x hybrids are composed of abundant catalytic centers, rich functionalities, and large specific surface areas, vast applications in energy transfer and energy storage fields can be realized. In this mini-review, we summarize the preparation strategies of MOF/COF-based hybrids, as well as their derivatives, nanostructure formation mechanism of M@CN_x and CN_x hybrids from MOF/COF-based hybrid materials, and their applications as catalysts for driving diverse reactions and electrode materials for energy storage. Further, current challenges and future prospects of applying these derivatives into energy conversion and storage devices are also discussed.