Highly Efficient Unitized Regenerative Hydrogen Peroxide Cycle Cell with Ultra-Low Overpotential for Renewable Energy Storage

Future large-scale application of intermittent renewable sourced energy requires low cost, efficient, and less resource-demanding energy storage systems for grid balancing. Conventional unitized regenerative fuel cells (URFCs) based on the water-H2 cycle are promising but suffer from high overpotential and low energy efficiency. Herein, we demonstrate a highly efficient unitized regenerative hydrogen peroxide (H2O2) cycle cell (UR-HPCC) for renewable energy storage. The prototype utilized a carbon-based platinum group metal-free (PGM-free) catalyst with atomically dispersed Co and N dopants (Co-N-C) as the bifunctional oxygen electrode catalyst for the hydrogen peroxide oxidation reaction (HPOR) and two-electron oxygen reduction reaction (2e-ORR) in H2O2 electrolyzer and fuel cell modes, respectively. This prototype showed a close-to-zero overpotential with a remarkably high round-trip efficiency of over 90%, which was attributed to the ideal catalytic properties of Co-N-C toward HPOR and 2e-ORR. Thermodynamic analysis of the above single-intermediate reactions suggests the intrinsic supremacy of UR-HPCC in energy efficiency and reversibility over conventional URFCs, paving the road to future sustainable distributed generation and energy storage systems.