Reconstruction and immobilization of polymolybdate induced by metal-organic coordination units for enhanced electrocatalytic hydrogen generation

Electrocatalytic water cracking for hydrogen evolution has drawn the concern from researchers owing to its high efficiency. Polymolybdate has excellent redox behaviors and O-rich surface, becoming attractive electrocatalytic materials. In this work, iso- and hetro-polymolybdate anions were introduced in the crystalline metal-organic coordination system as electrocatalytic electrode material for hydrogen evolution reaction. Semi-rigid bi-pyrazole bi-amide ligand was taken as the organic component, and four complexes were yielded under hydrothermal condition. The reconstruction and oriented immobilization of polymolybdate occur during the assembly of the architectures, owing to the potential template effect from the metal-organic units. This phenomenon influnce the distribution of active sites from polymolybdate. The discrete [AlMo6(OH)7O17]2- anions in complex 3 were immobilized among the directionally arranged metal-organic chains, and expose more active sites. The carbon cloth-based electrode modified by complex 3 possess obvious electrocatalytic activity by achieving a low overpotential of 17.0 mV at the current density of 10 mA cm-2 in 1 M KOH for hydrogen evolution reaction. Meanwhile, the overpotential can achieve 33.7 mV when the current density is 10 mA cm-2 in simulated seawater.