Topological Catalysis Driven by Symmetry-Protected Surface States

Topological surface states (TSSs) are widely considered to facilitate electrochemical reactions that are critical to producing clean energy and combating climate change, but direct evidence of such novel topological catalysis remains elusive due to obscuration by coexisting topologically trivial bulk states and surface dangling bonds. Here, we resolve this conundrum via a close examination of topological crystalline insulators (TCIs) SnX (X = Te, S, or Se). Unlike topological insulators used in prevailing studies, TCIs possess mirror-symmetry-protected TSSs that can be tuned via breaking of crystal symmetry with minimal impact on topologically trivial bulk and dangling bond states, thereby isolating the effects of TSSs on catalysis. These results demonstrate TSSs as a decisive driver for hydrogen and oxygen evolution reactions, offering compelling evidence for the long speculated yet hitherto unconfirmed phenomenon of topological catalysis and identify TCIs as a material class for superior catalytic performance.