Nitrogen reduction to ammonia is a requisite transformation for life and there is growing interest in developing sustainable technologies for ammonia synthesis using renewably sourced energy. Such approaches may some day lead to distributed on-demand fertilizer production and enable ammonia to be used as a zero-carbon alternative fuel. Our group has had an ongoing interest in fundamental studies of well-defined synthetic catalysts that mediate nitrogen reduction (N2R) to ammonia (or hydrazine), and related substrate reductions such as that of cyanide (CN–). We are especially interested in the operative mechanisms by which these catalysts operate, with an eye towards constraining mechanistic postulates for how nitrogenase enzymes function. We have recently been pursuing the idea that proton-coupled electron transfer (PCET) pathways for N2R can be more thermally efficient than step-wise ET/PT pathways and have tested this hypothesis via the development of electrochemical PCET (ePCET) mediators driven at potentials sufficiently anodic that the competing hydrogen evolution reaction (HER) is mitigated. We have also designed related electrocatalytic strategies that exploit an ET instead of a PCET mediator while still driving towards more thermally efficient transformations. In this talk I will describe our overall approach with some of our most recent findings. General mechanistic principles that emerge will be highlighted.