Bifunctional Electrocatalytic Activity of Two-Dimensional Metallophthalocyanine-Based Metal–Organic-Frameworks for Overall Water Splitting: A DFT Study

The design of efficient, low-cost, and easily integrable bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desirable for future renewable energy systems. By employing density functional theory (DFT)-based computations, we have investigated the catalytic activity of three transition metal (TM)-based two-dimensional (2D) metal–organic frameworks (MOFs), namely, TMPc_Cu_O MOFs (TM = Fe, Co, and Ni) for overall water splitting in the presence of a mixed (implicit + explicit) solvation model. These 2D TMPc_Cu_O MOFs (TM = Fe, Co, and Ni) are thermodynamically and electrochemically stable. Our calculations reveal that among these MOFs, CoPc_Cu_O MOF is the most efficient bifunctional electrocatalyst for overall water splitting with low HER/OER overpotentials of 0.11/0.65 V. We have further calculated the proton-coupled electron transfer (PCET) barrier for the potential-determining step (PDS) of HER/OER for CoPc_Cu_O MOF. Our finding on the PCET barrier for the HER and OER processes is that both the PDSs of HER/OER exhibit a surmountable barrier of 0.87/0.82 eV, suggesting facile kinetics. Therefore, based on the performance of CoPc_Cu_O MOF toward both HER and OER in terms of calculated overpotential and PCET barrier, we can conclude that CoPc_Cu_O MOF may be a potential bifunctional electrocatalyst toward overall water splitting.