Dual-Ligand Strategy to Construct Metal Organic Gel Catalyst with the Optimized Electronic Structure for High-Efficiency Overall Water Splitting and Flexible Metal-Air Battery

Non-noble metal catalysts are known for their efficient catalytic performance for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Metal organic gels (MOGs) can be considered as a promising electrocatalyst owing to the diverse physicochemical properties but usually suffer from its poor electrical conductivity and catalytic stability. Here, a FeCo-MOG is constructed with considerable trifunctional activity. The optimal P-CoFe-H3 prepared by using phytic acid (PA) and 2,4,6-Tris[(p-carboxyphenyl)amino]-1,3,5-triazine benzoic acid (H3TATAB) as dual ligands), exhibits outstanding ORR, OER, and HER activities as well as stability, exceeding most of state-of-the-art catalysts. As expected, the flexible Zn-air battery applied with P-CoFe-H3 as air cathode displays considerable power density, discharge voltage plateau, and cycling stability. Impressively, it is also capable of driving the overall water-splitting device by applying the P-CoFe-H3 as anode and cathode. Furthermore, theoretical calculations reveal that dual ligands can optimize the coordination environment and charge density of active sites, thereby reducing the absorption energy of intermediate species and boosting the catalytic performance. This work endows the dual-ligands coordination strategy with great potentiality for MOGs-based electrocatalysts in energy conversion devices. A dual-ligand assisted regulation strategy is proposed to fabricate the FeCo-metal organic gel (MOG) catalyst by assembling metal ions with PA and H3TATAB. The second ligand of H3TATAB effectively modulates the electronic structure of cobalt centers and achieves the well-exposed active Co sites for accelerating the electron transfer and catalytic kinetics. The optimal P-CoFe-H3 catalyst demonstrates excellent ORR, HER, and OER performance.image