Pd-O-Ti dual sites for efficient electrochemical active hydrogen generation and bromate reduction.

Atomic hydrogen (H*) plays a crucial role in electrochemical reduction technology towards various environmental and energy applications, but suffers from low utilization efficiency arisen from the undesirable H-H dimerization and the competitive adsorption between water molecule with reactants on the traditional adjacent catalytic sites. Herein, we anchored Pd single atoms on the naturally formed titanium oxide of titanium foam to construct Pd-O-Ti dual-site electrocatalyst with spatially isolated water dissociation and H* utilization site, which synchronously inhibits the H-H dimerization and the competitive adsorption of water molecule and targeted reactants. Experiments and theoretical calculations revealed that the Ti-O sites could synergistically dissociate water to H*, which overflowed to nearby Pd single-atom sites for designed reduction reactions and utilization benefiting from the hydrogen spillover ability of titanium oxide substrate. These Pd-O-Ti dual sites delivered almost 100 % bromate reduction efficiency with a rate constant of 1.57 h, far superior to those of Pd-O-Ti with adjacent Pd sites (0.52 h), Pd-N-C with single sites (0.04 h) and commercial Pd/C (0.18 h), respectively. This study sheds light on the importance of integrating synergistic active sites for complicated electrochemical reactions, and provide new insights in improving H* utilization for environmental remediation.