Cesium-anchored MB3 (M = Be, Ca, Sr) kagome monolayers: stabilizing active sites for bifunctional oxygen electrocatalysis

Abstract

Addressing urgent global energy demands, efficient multifunctional electrocatalysts are critical for next-generation clean energy technologies including fuel cells and metal–air batteries. Through systematic first-principles calculations, this work comprehensively evaluates 2D kagome MB₃ (M = Be, Ca, Sr) monolayers as promising electrocatalytic substrates. Transition metal single-atom decoration achieves exceptional bifunctional performance in Ni@CaB₃ with remarkably low oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) overpotentials of 0.37 V and 0.41 V, respectively. However, these gains are compromised by thermally induced metastability at 300 K, where heavy transition metal atoms migrate into kagome interlayers, distorting the active surface. We develop an innovative cesium anchoring strategy that suppresses atomic migration while preserving catalytic sites. Ni@CaB₃ maintains its OER activity (0.38 V) despite a moderate ORR overpotential increase to 0.60 V. Electronic analysis further reveals that Cs⁺ indirectly modulates the hydrogen evolution (HER) activity via boron-mediated charge transfer. This charge redistribution induces predictable shifts in the d-band centers of the transition metals, thereby rationally elevating the performance of Fe@CaB₃ above Mn@CaB₃. Beyond establishing Ni@CaB₃ as a prime bifunctional catalyst, this work resolves decoration-induced metastability in otherwise stable kagome lattices and delivers a generalizable stabilization paradigm applicable to engineered 2D electrocatalysts for sustainable energy conversion.