Nickel single atom catalyst supported on the gallium nitride monolayer: first principles investigations on the decisive role of support in the electrocatalytic reduction of CO₂

Designing efficient and low cost electrocatalysts for the reduction of CO2 to valuable chemicals is a sustainable way of mitigating and balancing its concentrations in the atmosphere which is essential for avoiding effects like climate change and global warming. Herein by means of systematic density functional theory simulations, we investigate the effect of support on the activity/selectivity of Ni based single atom catalyst (SAC) supported on GaN, MoS2, Mo2C, g-C2N and graphyne monolayers towards CO2 activation and reduction to different C-1 products. Our results reveal that the Ni SAC strongly binds on all the monolayer supports forming highly stable catalysts. The type of support plays a strong role in tuning the binding and activation of CO2 with Ni SAC supported on GaN and MoS2 monolayers showing the highest CO2 binding energies. Rigorous and in-depth electronic structure analysis reveals that the CO2 binding energy on these catalysts can be successfully rationalized in terms of electronic properties such as the d-band centre and integrated crystal orbital Hamilton populations. Moreover, the computed reaction pathways using the computational hydrogen electrode model indicate that the Ni SAC supported on the GaN monolayer can catalyse the CO2 reduction to CH3OH at a record low limiting potential of -0.28 V whereas the Ni SAC supported on the MoS2 monolayer catalyses CO2 reduction to HCOOH at a limiting potential of -0.42 V. Thus, our results show that the nature and type of support plays critical role in modulating the CO2 reduction activity/selectivity on these catalysts and provide insightful guidance for effective catalyst design for CO2 conversion to value added chemicals.