Why do Single‐Atom Alloys Catalysts Outperform both Single‐Atom Catalysts and Nanocatalysts on MXene?

Single‐atom alloys (SAAs), combining the advantages of single‐atom and nanoparticles (NPs), play an extremely significant role in the field of heterogeneous catalysis. Nevertheless, understanding the catalytic mechanism of SAAs in catalysis reactions remains a challenge compared with single atoms and NPs. Herein, ruthenium‐nickel SAAs (RuNiSAAs) synthesized by embedding atomically dispersed Ru in Ni NPs are anchored on two‐dimensional Ti3C2Tx MXene. The RuNiSAA‐3−Ti3C2Tx catalysts exhibit unprecedented activity for hydrogen evolution from ammonia borane (AB, NH3BH3) hydrolysis with a mass‐specific activity (rmass) value of 333 L min−1 gRu−1. Theoretical calculations reveal that the anchoring of SAAs on Ti3C2Tx optimizes the dissociation of AB and H2O as well as the binding ability of H* intermediates during AB hydrolysis due to the d‐band structural modulation caused by the alloying effect and metal‐supports interactions (MSI) compared with single atoms and NPs. This work provides useful design principles for developing and optimizing efficient hydrogen‐related catalysts and demonstrates the advantages of SAAs over NPs and single atoms in energy catalysis. The RuNi SAAs on MXene combine the multiple advantages of NPs, SAC, and MXene to promote rapid dehydrogenation of AB hydrolysis. RuNiSAA‐3−Ti3C2Tx with an optimal d‐band center achieves the highest activity (333 L min−1 gRu−1) toward AB hydrolysis.