Metaln+-Metalδ+ pair sites steer C-C coupling for selective CO2 photoreduction to C2 hydrocarbons
Weiwei Shao, Xiaodong Li, Juncheng Zhu, Xiaolong Zu, Liang Liang, Jun Hu, Yang Pan, Junfa Zhu, Wensheng Yan, Yongfu Sun, Yi Xie
Abstract
The major obstacle for selective CO2 photoreduction to C2 hydrocarbons lies in the difficulty of C-C coupling, which is usually restrained by the repulsive dipole-dipole interaction between adjacent carbonaceous intermediates. Herein, we first construct semiconducting atomic layers featuring abundant Metaln+-Metalδ+ pair sites (0 < δ < n), aiming to tailor asymmetric charge distribution on the carbonaceous intermediates and hence trigger their C-C coupling for selectively yielding C2 hydrocarbons. As an example, we first fabricate Co-doped NiS2 atomic layers possessing abundant Ni2+-Niδ+ (0 < δ < 2) pairs, where Co doping strategy can ensure higher amount of Ni2+-Niδ+ pair sites. In-situ Fourier-transform infrared spectroscopy, quasi in-situ Raman spectroscopy and density-functional-theory calculations disclose the Ni2+-Niδ+ pair sites endow the adjacent CO intermediates with distinct charge densities, thus decreasing their dipole-dipole repulsion and hence lowering the rate-limiting C-C coupling reaction barrier. As a result, in simulated flue gas (10% CO2 balance 90% N2), the ethylene selectivity for Co-doped NiS2 atomic layers reaches up to 74.3% with an activity of 70 µg·g−1·h−1, outperforming previously reported photocatalysts under similar operating conditions.