Interstitial Nonmetal Doping of Palladium-Based Catalysts for Alkyne Semihydrogenation

Selective hydrogenation of alkynes over Pd-based catalysts is a core industrial process for purifying crude alkenes from steam cracking and synthesizing high-value-added fine alkene chemicals. Despite extensive research efforts, achieving simultaneous improvement in alkene selectivity and catalytic activity remains a long-standing challenge, as traditional Pd site modulation strategies are inherently limited by the scaling relationships between alkyne and alkene adsorption energies. In recent years, interstitial nonmetal (e.g., B, C, N, P, S) doping has emerged as a promising modulation strategy to simultaneously boost alkyne conversion and alkene selectivity in Pd catalysis. The synergistic electronic and geometric effects induced by interstitial nonmetal atoms modulate the adsorption affinity of reactants and products, enabling Pd to preferentially adsorb alkynes, while simultaneously isolating active Pd ensembles or suppressing subsurface hydrogen formation, thereby enhancing the overall catalytic performance. In this review, we provide the first systematic overview of recent advances in interstitial nonmetal-doped Pd catalysts for selective alkyne hydrogenation, with an elaboration of their intrinsic modulation mechanisms. We begin by clarifying the fundamental mechanisms of Pd-catalyzed alkyne semihydrogenation, the limitations of traditional modification strategies, and the unique merits of interstitial nonmetal doping. Then, we highlight the catalytic performance and underlying modulation mechanisms of different interstitial nonmetal dopants for improving the selectivity of Pd catalysts in both thermocatalytic and electrocatalytic alkyne semihydrogenation. Finally, we outline the existing challenges and future perspectives for the development of high-performance interstitial nonmetal-doped Pd-based catalysts toward alkyne semihydrogenation.