The electrocatalytic reduction of CO₂ to produce sustainable fuels and chemicals is attracting great attention. Cu-based catalysts can lead to the production of a range of different molecules, and interestingly the product selectivity strongly depends on the preparation history, although it is not fully understood yet why. We report a novel strategy that allowed us to prepare Cu nanoparticle on carbon catalysts with similar morphologies, but prepared by in-situ reduction of either supported CuS, Cu₂S or CuO nanoparticles. For the first time the evolution of the Cu species was followed under CO₂ and H⁺ reduction conditions using in-situ X-ray absorption spectroscopy. Excellent electrochemical contact between the Cu-based nanoparticles, the carbon support and the carbon-paper substrate was observed, resulting in metallic Cu as the predominant phase under typical electrochemical CO₂ reduction conditions. Even covering less than 4% of the H₂ producing carbon support with Cu-sulfide derived nanoparticles allowed to steer the selectivity to a maximum of 12% Faradaic efficiency for the production of formate. Clear differences between the catalysts derived from CuS, Cu₂S or CuO nanoparticles were observed, which was ascribed to the presence of residual sulfur in the catalysts.

The conversion of synthesis gas (a mixture of hydrogen and carbon monoxide) to value-added chemicals has attracted significant attention in the past few years. Strong emphasis has been placed on enabling a process that allows the production of short olefins from synthesis gas, which can be derived from coal, biomass, or natural gas. Here, we introduce bifunctional catalysis to tailor the selectivity towards aromatics next to olefins by combining an iron-based Fischer–Tropsch to olefins catalyst with the acid function of a zeolite. Olefins were formed from synthesis gas on an iron-based catalyst and partly converted to aromatics on the acid sites of the zeolite. Surprisingly, this aromatization did not follow the pathway of hydrogen transfer, whereby three paraffin molecules are produced for every aromatic molecule formed, which allowed us to obtain carbon selectivity towards chemicals (sum of lower olefins and aromatics) of 70–80 % at 1 bar reaction pressure. Increasing the partial pressure of hydrogen led to substantial hydrogenation of olefins towards paraffins.

Magnesium hydride has been studied extensively for applications as a hydrogen storage material owing to the favourable cost and high gravimetric and volumetric hydrogen densities. However, its high enthalpy of decomposition necessitates high working temperatures for hydrogen desorption while the slow rates for some processes such as hydrogen diffusion through the bulk create challenges for large-scale implementation. The present paper reviews fundamentals of the Mg–H system and looks at the recent advances in the optimisation of magnesium hydride as a hydrogen storage material through the use of catalytic additives, incorporation of defects and an understanding of the rate-limiting processes during absorption and desorption.

A detailed structural analysis of Mg-Ti-H thin films reveals the presence of a chemically partially segregated but structurally coherent metastable phase. By combining X-Ray Diffraction and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy on Mg_yTi_1-yH_x thin films we find non-zero Chemical Short-Range Order (CSRO) parameters for all the compositions measured. Despite the positive enthalpy of mixing of Mg and Ti the degree of ordering does not increase upon loading and unloading with hydrogen. The robustness of this system and the fast and reversible kinetics of hydrogen loading and unloading are caused by the formation of nanoscale compositional modulations in the intermetallic alloy. This microstructure is responsible for the exceptional properties of Mg_yTi_1-yH_x thin films. It also shows that reversible metastable metal-hydrides offer new possibilities for hydrogen storage, beyond the limits imposed by thermodynamic equilibrium.