Abstract
Ni-based catalysts are considered to be promising candidates for moderate-low temperature (200-400 °C) reverse water-gas shift (MLT-RWGS) as an important CO(2) reduction pathway. However, their high activation properties for CO inevitably lead to severe methanation at high CO(2) conversion, creating an activity-selectivity trade-off and unsatisfactory CO yields. Here, a novel supported Ni-based catalyst is deveolped, consisting of abundant Ni(δ+) atoms anchored in situ on ultrathin Ni-phyllosilicate nanosheet (a-Ni(δ+)-PSNS(400), 0< δ ≤1). The a-Ni(δ+)-PSNS(400) break activity-selectivity trade-off and achieve high CO selectivity (92%) toward at a formation rate of 21.0 mmol(CO) h(-1) gcat(-1), outdistancing those of all prevailing Ni-based catalysts for MLT-RWGS. Such catalytic performance is attributed to unique geometric/electronic effects of a-Ni(δ+)-PSNS(400), i.e., exposed monodisperse Ni(δ+) atoms with low electron density on ultrathin Ni-phyllosilicate nanosheet. The ultrathin nanosheet enables anchored Ni(δ+) atoms to fully expose and disperse, boosting atom-utilization efficiency and atom-synergistic effects, endowing them with high catalytic activity; while low electron density of Ni(δ+) atoms extremely weakens their chemical adsorption of CO, preventing further CO hydrogenation into CH(4), which ensures their high CO selectivity. This work provides new insights into the design of active microstructures of high-performance Ni-based catalysts for synchronous high activity-selectivity.