Electrochemical Ruthenium-Catalysed C–H Activation in Water Through Heterogenization of a Molecular Catalyst

Efficient catalytic oxidative C–H activation of organic substrates remains an important challenge in synthetic chemistry. Here, we show that the combination of a transition metal catalyst, surface immobilisation and an...

Copper(II) tetrakis(pentafluorophenyl)porphyrin: Highly Active Copper-based Molecular Catalyst for Electrochemical CO2 Reduction

We report a highly active copper-based catalyst for electrochemical CO2 reduction. Electrochemical analysis revealed that the maximum turnover frequency for CO2 to CO conversion reached to 1,460,000 s-1 at an...

A ruthenium-based catalyst on carbon electrodes for electrochemical water splitting

Electrochemical water splitting constitutes one of the most promising strategies for converting water into hydrogen-based fuels, and this technology is predicted to play a key role in our transition towards a carbon-neutral energy economy. To enable the design of cost-effective electrolysis cells based on this technology, new and more efficient anodes with augmented water splitting activity and stability will be required. Herein, we report an active molecular Ru-based catalyst for electrochemically-driven water oxidation and two simple methods for preparing anodes by attaching this catalyst onto multi-walled carbon nanotubes. The anodes modified with the molecular catalyst were characterized by a broad toolbox of microscopy and spectroscope techniques, and interestingly no RuO2 formation was detected during electrocatalysis over 4 h. These results demonstrate that the herein presented strategy can be used to prepare anodes that rival the performance of state-of-the-art metal oxide anodes.

Tandem electrocatalytic N2 fixation via concerted proton-electron transfer

New electrochemical ammonia (NH3) synthesis technologies are of interest as a complementary route to the Haber-Bosch (HB) process for distributed fertilizer generation, and towards exploiting ammonia as a zero-carbon fuel produced via renewably-sourced electricity.1–4 Apropos of these goals is a surge of fundamental research targeting heterogeneous materials5–7 as electrocatalysts for the nitrogen reduction reaction (N2RR). These systems generally suffer from poor stability and NH3 selectivity; competitive hydrogen evolution reaction (HER) outcompetes N2RR.8 Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy,9 but progress has thus far been thwarted by the same selectivity issue; HER dominates. Herein we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N2 reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate concerted proton-electron transfer (CPET) steps, facilitating N−H bond formation at a favorable applied potential and overall thermodynamic efficiency. Without CPET, certain intermediates of the N2RR cycle would be unreactive via independent electron transfer (ET) or proton transfer (PT) steps, thereby shunting the system. Promisingly, complexes featuring several metals (W, Mo, Os, Fe) achieve N2RR electrocatalysis at the same applied potential in the presence of the CPET mediator, pointing to the generality of this tandem approach.

Tandem electrocatalytic N2 fixation via concerted proton-electron transfer

New electrochemical ammonia (NH3) synthesis technologies are of interest as a complementary route to the Haber-Bosch (HB) process for distributed fertilizer generation, and towards exploiting ammonia as a zero-carbon fuel produced via renewably-sourced electricity. Apropos of these goals is a surge of fundamental research targeting heterogeneous materials as electrocatalysts for the nitrogen reduction reaction (N2RR). These systems generally suffer from poor stability and NH3 selectivity; competitive hydrogen evolution reaction (HER) outcompetes N2RR. Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy, but progress has thus far been thwarted by the same selectivity issue; HER dominates. Herein we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N2 reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate concerted proton-electron transfer (CPET) steps, facilitating N−H bond formation at a favorable applied potential and overall thermodynamic efficiency. Without CPET, certain intermediates of the N2RR cycle would be unreactive via independent electron transfer (ET) or proton transfer (PT) steps, thereby shunting the system. Promisingly, complexes featuring several metals (W, Mo, Os, Fe) achieve N2RR electrocatalysis at the same applied potential in the presence of the CPET mediator, pointing to the generality of this tandem approach.

Selective Catalytic Conversion of Acetylene to Ethylene Powered by Water and Visible Light

The production of polymer-grade ethylene requires the purification of ethylene feed from acetylene contaminant. Accomplishing this task by state-of-the-art thermal hydrogenation requires high temperature, external feed of H2 gas, and noble metal catalysts, and is not only expensive and energy-intensive but also prone to overhydrogenate to ethane. We report a photocatalytic system to reduce acetylene to ethylene with >99% selectivity for ethylene under both non-competitive (no ethylene co-feed) and competitive (ethylene co-feed) conditions, and near 100% conversion under the latter industrially relevant condition. Our system uses a molecular catalyst based on earth-abundant cobalt operating under ambient conditions and sensitized by either [Ru(bpy)3]2+ or an inexpensive organic semiconductor (mpg-CN) under visible light. These features and the use of water as a proton source offer substantial advantages over current hydrogenation technologies with respect to selectivity and sustainability.