Identifying And Unveiling the Role of Multivalent Metal States for Bidirectional UOR and HER Over Ni, Mo-Trithiocyanuric Based Coordination Polymer.

Urea oxidation reaction (UOR), an ideal alternative to oxygen evolution reaction (OER), has received increasing attention for realizing energy-saving H 2 production and relieving pollutant degradation. Normally, most studied Ni-based UOR catalysts pre-oxidate to NiOOH and then act as active sites. However, the unpredictable transformation of the catalyst's structure and its dissolution and leaching, may complicate the accuracy of mechanism studies and limit its further applications. Herein, a novel self-supported bimetallic Mo-Ni-C 3 N 3 S 3 coordination polymers (Mo-NT@NF) with strong metal-ligand interactions and different H 2 O/urea adsorption energy are prepared, which realize a bidirectional UOR/hydrogen evolution reaction (HER) reaction pathway. A series of Mo-NT@NF is prepared through a one-step mild solvothermal method and their multivalent metal states and HER/UOR performance relationship is evaluated. Combining catalytic kinetics, in situ electrochemical spectroscopic characterization, and density-functional theory (DFT) calculations, a bidirectional catalytic pathway is proposed by N, S-anchored Mo 5+ and reconstruction-free Ni 3+ sites for catalytic active center of HER and UOR, respectively. The effective anchoring of the metal sites and the fast transfer of the intermediate H* by N and S in the ligand C 3 N 3 S 3 H 3 further contribute to the fast kinetic catalysis. Ultimately, the coupled HER||UOR system with Mo-NT@NF as the electrodes can achieve energy-efficient overall-urea electrolysis for H 2 production.