In Situ Dynamic Nanostructuring of the Cu-Ti Catalyst-Support System Promotes Hydrogen Evolution under Alkaline Conditions.

We report an interesting case of in situ dynamic nanostructuring of catalyst and support under hydrogen evolution conditions in basic media. When solution-grown CuO nanoplates on titanium substrates are subjected to hydrogen evolution reaction, besides the reduction of CuO to metallic Cu nanoplates, both catalyst and support simultaneously undergo a nanostructuring process. The process is driven by the dissolution-redeposition of Cu and the alkaline etching of the titanium support. The morphology of the resulting nanocomposite material consists of a porous matrix made of ultrasmall Cu nanocrystals and amorphous TiO x nanoparticles. Interestingly, the nanostructuring of the catalyst can be finely controlled by varying the applied potential. Such a process leads to a 5.4-fold improvement in the catalyst activity, which is attributed not only to its large active surface area (formed upon nanostructuring), but also to an improved water dissociation activity, provided by the in situ formation of TiO x nanoparticles. The final catalyst exhibits -10 mA/cm2 of current density at a small overpotential of -108 mV and a long-term operational stability up to 50 h. Density functional theory calculations show that the co-presence of Cu and TiO2 nanoparticles optimizes the free energy of hydrogen adsorption in the final catalyst. Our work highlights the importance of studying the dynamic evolution of catalysts under operational conditions and choice of proper support that enhances the catalyst activity.