Steering deep CO2 reduction to C3+ hydrocarbons on nickel-based catalysts via ligand modification

Abstract

Electrochemical CO₂ reduction is a promising approach to produce synthetic fuels and chemicals. Nickel-based catalysts have been shown to reduce CO₂ toward long-chain hydrocarbons, whereas selectivity remains limited due to inefficient C–C coupling. We report a ligand-engineering strategy to modulate the electronic properties of a nickel hydroxide catalyst by surface cysteamine modification (Ni-OH-c) to boost the generation of C₃₊ hydrocarbons. Structural and compositional characterization showed that carbon-supported amorphous Ni(OH)₂ nanosheets were reconstructed in situ into ultrasmall crystalline Ni(OH)₂ nanoparticles. More importantly, surface cysteamine donates an electron to Ni(OH)₂, thus increasing the surface electron density of Ni(OH)₂ and creating interfacial Ni^δ+/Ni²⁺ sites. Electrochemical measurements showed that, compared with pristine Ni(OH)₂, Ni-OH-c significantly promoted deep CO₂ reduction and C–C coupling, presenting a C₃₊ hydrocarbons faradaic efficiency of 1.88% and a partial current density of 0.31 mA cm⁻². We demonstrated stable C₃₊ hydrocarbon generation for over 13 h. In situ spectroscopic investigation revealed that cysteamine modification facilitated the adsorption of bridge-bonded *CO, which promoted *CO hydrogenation and enabled facile asymmetric *CO–COH coupling, thereby enabling the preferential generation of C₃₊ hydrocarbons. These findings offer an effective platform toward rational design of high-performance Ni-based non-Cu catalysts for selective synthesis of valuable long-chain feedstocks from direct CO₂ reduction.