One of the main research challenges for electrocatalysis that produces carbon-containing products from CO2 is avoiding the competing hydrogen evolution reaction. Instead of totally eliminating hydrogen, our approach makes use of the readily available protons in aqueous electrolyte to co-produce CO and H2, making synthesis gas (syngas) with a tunable CO:H2 ratio. The resulting syngas can then be used as feedstock for existing thermocatalytic processes, such as Fischer–Tropsch and methanol synthesis reactions [1]. We will present our results in identifying palladium hydride (PdH), formed under electrocatalytic reaction conditions, as an effective electrocatalyst that enables the syngas production [2]. We will also report our efforts in reducing the loading of Pd by alloying Pd with inexpensive secondary metals, supporting Pd on transition metal carbides and nitrides, and utilizing single atom Pd catalysts. For each type of the catalysts, we monitor the phase transition from Pd to PdH under reaction conditions with in-situ synchrotron-based X-ray absorption and X-ray diffraction techniques. We also identify descriptors for syngas production on PdH, bimetallic PdH, and supported PdH catalysts by performing DFT calculations of the effect of PdH formation on the binding strength of reaction intermediates. The research methodology established here should be useful not only for continued optimization of Pd-based syngas-producing electrocatalysts, but also for enhancing activity while reducing the loading of precious metals for other electrocatalytic applications.

Electrocatalytic conversion of CO2 to syngas with controlled CO/H2 ratios

ACS Spring 2022

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