Immobilization of a Molecular Re Complex on MOF-derived Hierarchical Porous Carbon for CO2 Electroreduction in Water/Ionic Liquid Electrolyte.

The development of molecular catalysts for CO2 electroreduction within electrolyzers requests their immobilization on the electrodes. While a variety of methods have been explored for the heterogenization of homogeneous complexes, a novel approach using a hierarchical porous carbon material, derived from a metal-organic framework, is reported as a support for the well-known molecular catalyst [Re(bpy)(CO)3 Cl] (bpy=2,2'-bipyridine). This cathodic hybrid material, named Re@HPC (HPC=hierarchical porous carbon), has been tested for CO2 electroreduction using a mixture of an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIM) and water as the electrolyte. Interestingly, it catalyzes the conversion of CO2 into a mixture of carbon monoxide and formic acid, with a selectivity that depends on the applied potential. The present study thus reveals that Re@HPC is a remarkable catalyst, enjoying excellent activity (turnover numbers for CO2 reduction of 7835 after 2 h at -1.95 V vs. Fc/Fc+ with a current density of 6 mA cm-2 ) and good stability. These results emphasize the advantages of integrating molecular catalysts onto such porous carbon materials for developing novel, stable and efficient, catalysts for CO2 reduction.

Zn-Cu Alloy Nanofoams as Efficient Catalysts for the Reduction of CO2 to Syngas Mixtures with a Potential-Independent H2 /CO Ratio.

Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 versus H+ reduction. By varying the Zn/Cu ratio, tailored syngas mixtures are obtained without the production of other gaseous products, which is attributed to preferential CO- and H2 -forming pathways on the alloys. The syngas ratios are also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis with renewable power sources that have fluctuating intensity. As such, industrially relevant syngas ratios are achieved at large currents (-60 mA) for extensive operating times (>9 h), demonstrating the potential of this strategy for fossil-free fuel production.