Operando Reconstruction of NiB Precatalyst Into Adaptive Heterointerfaces for CO₂ Photoreduction via Tandem Hydrogen...

Photocatalytic CO₂ reduction is a transformative carbon neutrality technology, yet the electronic competition between water-derived proton generation and CO₂ activation over intrinsic sites leads to parasitic H₂ evolution over a static catalytic surface. Here we demonstrate that crystalline nickel boride (NiB) precatalyst, previously unexplored for photocatalysis, undergoes spontaneous operando reconstruction under illumination to form adaptive Ni/B₂O₃/NiB heterointerfaces as the genuine catalytically active phases. The reaction-driven reconstructed interfaces enable a tandem hydrogen relay across the NiB→Ni→B₂O₃ interface, in which hydrogen species evolve sequentially from H₂O to H₂ and are subsequently converted into surface-active hydrogen (H₂O→H₂→H*) via Ni-mediated dissociation and hydrogen spillover. The H* species assist CO₂ activation and hydrogenation on the electron-deficient B₂O₃ domains. This dynamic process progressively redirects the reaction pathway from water-splitting-dominated activity to highly efficient CO₂-to-CO conversion, achieving a CO evolution rate of 4.5 mmol·g^-1·h^-1 with promoted utilization of in situ formed hydrogen species, thus presenting an order-of-magnitude enhancement over reported photocatalytic systems. This work unlocks crystalline transition-metal borides as an untapped material platform for photocatalytic CO₂ reduction and demonstrates that reaction-driven interfacial reconstruction can establish adaptive hydrogen-relay pathways to mitigate multi-reaction competition in solar-to-chemical conversion.