Another form of spatial control that has been beneficial for integrated catalysis is the generation of local concentration gradients, which can be conveniently achieved electrochemically. Depending on the steepness of the gradient, areas rich or void of certain species may be regarded as loosely defined compartments. For example, a recent report from Liu and coworkers employed a nanowire-array electrode to pair the seemingly incompatible CH4 activation by an O2-sensitive rhodium(II) metalloradical with O2-based oxidation for CH3OH formation (FIG. ). The application of a reducing potential to the nanowire array electrode created a steep O2 gradient within the wire array electrode, and an anoxic compartment was established at the bottom of the wires. As a result, a catalytic cycle was formed in which the air-sensitive Rh(II) activated CH4 in the O2-free region of the wire array electrode, while CH3OH synthesis proceeded in the aerobic domain with O2 as the terminal electron acceptor. Such a result was unattainable without the nanowire array electrode (i.e., using a planar electrode). The detainment of the ephemeral Rh(II) intermediate by the nanowire electrode for catalytic CH4-to-CH3OH conversion encourages further exploration of the design principles of compartmentalizing cascades for higher turnover while mitigating deactivation pathways. Integrated catalysis can generate highly complex products through different aspects, such as a precisely controlled macromolecular structure or surface-patterning polymerization. Besides regulating polymer structures by switchable catalysis (see above), Byers, Wang, and coworkers employed spatiotemporal control to synthesized patterned polymer-functionalized surfaces (FIG. ). This work involved immobilizing a redox-switchable bis(imino)pyridine iron polymerization catalyst similar to that described above on semiconducting TiO2 nanoparticles. Application of the functionalized nanoparticles to conducting fluorine-doped tin oxide (FTO) surfaces led to electroactive surfaces whose chemoselectivity for polymerization reactions can be altered through the application of an electrical current: surfaces with the catalyst in the iron(II) oxidation state react with lactide to form polyesters while surfaces with the iron(III) oxidation state react with epoxides to form polyethers. By using FTO substrates that contain electrically isolated zones of the functionalized TiO2 nanoparticles, patterned surfaces containing polyesters and polyethers can be synthesized by applying oxidizing potentials to zones where polyethers are desired. Such surfaces have many applications from sensors to applications in the electronics industry.