Power-to-X concepts promise a reduction of greenhouse gas emissions simultaneously guaranteeing a safe energy supply even at high share of renewable power generation, thus becoming a cornerstone of a sustainable energy system. Power-to-syngas, that is, the electrochemical conversion of steam and carbon dioxide with the use of renewably generated electricity to syngas for the production of synfuels and high-value chemicals, offers an efficient technology to couple different energy-intense sectors, such as "traffic and transportation" and "chemical industry". Syngas produced by co-electrolysis can thus be regarded as a key-enabling step for a transition of the energy system, which offers additionally features of CO -valorization and closed carbon cycles. Here, we discuss advantages and current limitations of low- and high-temperature co-electrolysis. Advances in both fundamental understanding of the basic reaction schemes and stable high-performance materials are essential to further promote co-electrolysis.

High-temperature co-electrolysis of carbon dioxide and steam is a promising method to produce 'white' syngas by making use of renewable energy and carbon dioxide as sustainable feedstock. The technological key advantage is the possibility to tailor syngas compositions over a broad range. This paper presents a systematic investigation of the syngas tailoring process by establishing relationships between feed gas compositions and flow rates to the syngas ratio. A linear dependence between the H 2 O:CO 2 ratio in the feed gas and the H 2 :CO ratio in the output gas was observed. Furthermore, the syngas ratio remains mostly invariant upon variations in electrochemical potential and fluctuating gas utilizations/flow rates during operation of a co-electrolysis cell. Most importantly, the co-electrolysis performance was demonstrated to operate at high current densities of up to 3.2 A•cm −2 over a broad range of feed gas compositions with faradaic efficiencies of nearly 100%. The possibility to operate co-electrolysis under transient load conditions renders this method particularly suitable in future scenarios of intermittent availability of renewables. The results described here illustrate the versatility of co-electrolysis, which can produce all relevant syngas compositions in a single-step process at constantly high performance.

Chemical industries rely heavily on fossil resources for the production of carbon-based chemicals. A possible transformation towards sustainability is the usage of carbon dioxide as a source of carbon. Carbon dioxide is activated for follow-up reactions by its conversion to carbon monoxide. This can be accomplished by electrochemical reduction in solid oxide cells. In this work, we investigate the process performance of the direct high-temperature CO2 electrolysis by current-voltage characteristics (iV) and Electrochemical Impedance Spectroscopy (EIS) experiments. Variations of the operation parameters temperature, load, fuel utilization, feed gas ratio and flow rate show the versatility of the procedure with maintaining high current densities of 0.75 up to 1.5 A·cm−2, therefore resulting in high conversion rates. The potential of the high-temperature carbon dioxide electrolysis as a suitable enabler for the activation of CO2 as a chemical feedstock is therefore appointed and shown.

Formic acid is considered a promising energy storage medium, and its selective dehydrogenation enables the generation of high-purity H2. Herein we report a bipyridine-based conjugated microporous polymer (CMP) loaded with [Cp*IrCl2]2 for the base-free aqueous dehydrogenation of formic acid to H2/CO2. This catalyst exhibits high activity and selectivity at temperatures over 130 °C and with formic acid concentrations as high as 10 M. Recycling tests demonstrate a low Ir leaching and a gradual increase in the activity over six runs and a low CO content in the gas phase of about 138 ppm. TOFs of up to 123894 h–1 were obtained using 0.1 wt % Ir loading.

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