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