MXene quantum dots-Co(OH)2 heterojunction stimulated Co2+δ sites for boosted alkaline hydrogen evolution

Abstract

Persevering structural stability of the active species after phase reconfiguration poses a key challenge for various sustainable catalytic systems. In this study, we construct a robust β-Co(OH)₂ electrocatalyst via self-adaptive coordination of MXene quantum dots (MQDs) during phase transition from the Co₂(OH)₃Cl precursor to β-Co(OH)₂ (MQDs/β-Co(OH)₂/Co foam). The heterojunction induced the excellent electron transfer, causing the lattice strain of β-Co(OH)₂, and the accumulated electrons at the MQDs end regulated the electronic density of Co sites (Co^2+δ), reversing the structural instability of β-Co(OH)₂ within the applied reduction potential range. Furthermore, density functional theory calculation confirms the role of well-matched heterogeneous interfaces in HER. The result shows the high-valance Co^2+δ sites promote adsorption and dissociation of H₂O, increasing proton supply and accelerating reaction rate. Concurrently, MQDs facilitate the adsorption of hydrogen intermediates and H₂ generation. Our architected catalyst exhibited exceptional alkaline hydrogen evolution reactions (HERs) performance (91 mV@10 mA cm⁻²) and superior stability outperforms most reported β-Co(OH) ₂-based catalysts. Our work demonstrates the efficacy of MQDs as co-catalysts in enhancing the activity and structural stability of catalysts.