Design of a Porous Silver Metal–Organic Cage with Accessible Ag(I) Active Sites for Enhanced Hydrogen Evolution Reaction in Alkaline Water

This work elucidates the design, synthesis, and characterization of AgMOC-1, an Ag(I)-based metal–organic cage. Crystallographic analysis reveals trigonal coordination of Ag with a large void and a high Brunauer–Emmett–Teller surface area of 172.8 m2/g. AgMOC-1 exhibited an excellent Tafel slope of 74 mV dec–1, indicating faster kinetics via the Volmer–Heyrovsky mechanism. Computational calculations attribute accessible Ag-site favored by porous morphology-driven H* adsorption with a near-optimal hydrogen adsorption free energy (ΔG*H) value of −0.02 eV, endorsing excellent electrocatalytic hydrogen evolution. AgMOC-1 displayed good activity and stability over the period of 3 h. However, on prolonged operation, controlling potential electrolysis at −0.51 V (V vs RHE) for 24 h revealed the structural and morphological transformation of AgMOC-1 to corresponding catalytically active Ag2O species, as justified through powder X-ray diffraction, FT-IR, SEM, and EDX analysis. Analytical, morphological, and computational analyses consolidate that the synergistic interplay of tailored porosity and accessible Ag-active sites for efficient hydrogen evolution reaction (HER) offers promising insights into the development of next-generation HER materials.