Harnessing self-tuned strain: Strain can modify the electronic properties of a metal and has provided a method for enhancing electrocatalytic activity. For practical catalysts, nanomaterials with high surface areas are needed. However, for nanoparticles, strain is often induced with overlayers (adsorbates or heteroatoms) that can undergo reconstruction during operation that releases the induced strain. Wang et al. show that freestanding palladium nanosheets (three to five monolayers thick) form with an internal compressive strain of 1 to 2% and can be much more active for both the oxygen and hydrogen evolution reactions under alkaline conditions compared with nanoparticles. Science , this issue p. 870

The local pH on electrode surfaces is known to play an important role in the electrochemical reduction of CO₂, which could alter the chemical kinetics and molecular transport under the reaction conditions. Here we report the study of local pH effect on the catalytic performance of high-surface-area Cu electrocatalysts. The electroreduction of CO₂ was systematically investigated on three types of Cu nanowires with distinct surface roughness factors and nanostructures. The measured electrocatalytic activities and selectivities were further correlated to the simulated local pH on the electrode surface. It was revealed that the high local pH induced by the production of hydroxide from the reaction beneficially suppresses the evolution of hydrogen and enhances the selectivity toward multi-carbon products, but detrimentally limits the transport of CO₂ molecules at large current densities. An optimal range of local pH is determined for the electroreduction of CO₂, which is insightful for improving the design of electrodes for more efficient energy conversion and chemical transformations.