A typical design of a molecularly modified electrode, as discussed in Section 2, often starts with an optimized molecular catalyst for a specific type of reaction with an electrode support as the electron source. However, the logic of such a design lies in the assumption that the activity of the molecular catalyst translates invariably after heterogenization. In Section 3.1, we described the impact on the activity of the immobilized molecular catalyst. Studies have shown that the immobilization method dramatically affects the reactivity of the resulting system. Here we will include cases studying covalent linkage effects on electron transfer, reactivity, and reaction mechanism of the appended molecular catalyst on energy conversion reactions. It is essential to realize the significance of electron transfer on the modified surface in electrocatalysis. In the previous example shown in Figure , an intermolecular electron transfer (from the electrode to ferrocene) was observed at different rates depending on the distance between the electrode and the redox-active species for non-covalent immobilization. In addition, the efficiency of electron transfer is found to be affected by the conjugation degree of the tether. In an extreme example involving full conjugation between the electrode and the chemical modification, a concerted protonelectron transfer pathway typically observed for metal electrode surfaces was achieved. This observation is contrary to the well-known stepwise mechanism of molecular electrocatalysis, where electron transfer and substrate activation are separated. A detailed study by Surendranath and coworkers demonstrated that such mechanistic changes could be obtained by strong electronic coupling between the immobilized molecule and the electrode and could be affected by changing solvents. In the following section, we will start with a general introduction of the strategy to form strongly coupled linkages with examples demonstrating subsequent effects on electron transfer and catalytic activity. We will discuss the mechanistic changes by comparing strongly coupled and weakly coupled linkages. Lastly, we include covalent linkages commonly employed involving electrografting and "click" reactions along with the benefits of enhancing catalytic activity and improving catalyst lifetime.