Harnessing Support-Dependent Hydrogen Spillover for Ni-Based CO₂ Hydrogenation

Hydrogen spillover has long been recognized as a ubiquitous phenomenon in heterogeneous catalysis, yet its rational utilization has been hindered by the lack of design principles accounting for its support dependence. The present work demonstrates that support-dependent hydrogen spillover can be harnessed to promote Ni-based CO₂ hydrogenation. This is achieved by physically mixing Ni catalysts with Pt-containing co-catalysts, which initiates hydrogen spillover. Systematic comparisons across oxide supports reveal that catalytic promotion occurs only when spilled hydrogen diffuses on the support surface rather than into the bulk, highlighting the decisive role of support-dependent spillover pathways. As a consequence, the intrinsic catalytic performance of Ni is markedly enhanced, reaching activity levels comparable to those of the highest reported Ni-based CO₂ hydrogenation catalysts. Mechanistic investigations further show that hydrogen spillover plays distinct roles depending on support reducibility. On moderately reducible oxides, spilled hydrogen rapidly removes poisoning oxygen species that are formed during CO₂ activation on Ni nanoparticles, whereas on highly reducible oxides, it facilitates the formation of interfacial oxygen vacancies that promote bicarbonate formation as a key reaction intermediate. These findings establish support-dependent hydrogen spillover as a versatile design principle that enables exceptional Ni-based CO₂ hydrogenation performance without any modification of the Ni structure itself.