Lattice compression in arrayed CoMoO₄: A synergistic coordination strategy with graphdiyne and PMo₁₂ for enhanced AEM water electrolysis

Strain engineering and coordination modulation represent effective and precisely tunable strategies for improving water-splitting efficiency. In this study, a substrate-induced synthesis strategy is proposed, in which pyrgraphdiyne nanowalls serve as a template to achieve controllable in situ growth of a three-dimensional CoMoO₄ nanoarray with lattice compressive strain. On this base, polyoxometalate clusters bond with exposed cobalt sites, allowing fine-tuning of the axial coordination environment of Co sites. The resulting Co-O-Mo bonds act as efficient electron transport pathways, further optimizing the electronic structure of the metal active centers. Benefiting from this design, the PMo₁₂-CoMoO₄/PGDY catalyst with 4.2% lattice compressive strain exhibits excellent bifunctional activity, achieving OER overpotentials of 187 mV at 10 mA cm⁻² and 364 mV at 1000 mA cm⁻², and HER overpotential of 45 mV at 10 mA cm⁻² in 1 M KOH. Notably, in an AEMWE single-cell configuration, this catalyst achieves a high current density of 1000 mA cm⁻² at 1.77 V and maintains robust stability for 200 h under practical operating conditions. This work demonstrates a universal substrate-driven design paradigm that synergistically integrates lattice strain engineering with coordination modulation, offering a new route to bifunctional noble-metal-free electrocatalysts. The enhanced performance arises from two synergistic effects: (i) PGDY-induced lattice compression (4.2%) optimizes Co-O bond lengths and the D-band center, reducing the OER free energy barrier; and (ii) axial coordination of PMo₁₂ tunes the electronic structure of Co sites and promotes interfacial charge transfer via Co-O-Mo bonds.