At the Crespilho Group, our research sits at the interface of electrochemistry, molecular biophysics, and advanced materials engineering to transform how we understand and harness biological energy systems. To unravel the fundamental mechanisms governing biological energy conversion, we investigate quantum bioelectrochemistry, focusing on electron transfer dynamics, protein conductance, quantum coherence, and molecular-scale charge transport. To capture these complex interfacial processes as they happen, we utilize operando bioelectrochemistry, coupling electrochemistry with advanced spectroscopic techniques—including operando X-ray, FTIR, Raman, UV-Vis, and EPR—to obtain precise structural and mechanistic insights under real operational conditions. Drawing inspiration from nature's unmatched efficiency, we design bioinspired electrocatalysts by integrating natural enzymes, artificial proteins, and biomimetic catalysts to drive vital chemical transformations, particularly CO2 conversion and solar fuel production. We translate these foundational molecular insights into functional applications by engineering bioelectronics and biosensors, developing flexible sensors, point-of-care testing (POCT) systems, living interfaces, and bioelectronic architectures for real-time biological monitoring. Finally, we apply these advanced biological interfaces to address global energy challenges through sustainable energy technologies, pioneering biobatteries, organic batteries, biofuel cells, and engineered living materials that pave the way for next-generation, eco-friendly energy storage and conversion.