Graphite conjugated nickel phthalocyanine for efficient CO2 electroreduction and Zn-CO2 batteries.

The linking chemistry between molecular catalysts and substrates is a crucial challenge for enhancing electrocatalytic performance. Herein, we elucidate the influence of various immobilization methods of amino-substituted Ni phthalocyanine catalysts on their electrocatalytic CO2 reduction reaction (eCO2RR) activity. A graphite-conjugated Ni phthalocyanine, Ni(NH2)8Pc-GC, demonstrates remarkable electrocatalytic performance both in H-type and flow cells. In situ infrared spectroscopy and theoretical calculations reveal that the graphite conjugation, through strong electronic coupling, increases the electron density of the active site, reduces the adsorption energy barrier of *COOH, and enhances the catalytic performance. As the cathode catalyst, Ni(NH2)8Pc-GC also displays remarkable charge-discharge cycle stability of over 50 hours in a Zn-CO2 battery. These findings underscore the significance of immobilization methods and highlight the potential for further advancements in eCO2RR.

Efficient Visible-Light-Driven Carbon Dioxide Reduction using a Bioinspired Nickel Molecular Catalyst.

Inspired by natural enzymes, this study presents a nickel-based molecular catalyst, [Ni‖(N2S2)]Cl2 (NiN2S2, N2S2=2,11-dithia[3,3](2,6)pyridinophane), for the photochemical catalytic reduction of CO2 under visible light. The catalyst was synthesized and characterized using various techniques, including liquid chromatography-high resolution mass spectrometry (LC-HRMS), UV-Visible spectroscopy, and X-ray crystallography. The crystallographic analysis revealed a slightly distorted octahedral coordination geometry with a mononuclear Ni2+ cation, two nitrogen atoms and two sulfur atoms. Photocatalytic CO2 reduction experiments were performed in homogeneous conditions using the catalyst in combination with [Ru(bpy)3]Cl2 (bpy=2,2'-bipyridine) as a photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as a sacrificial electron donor. The catalyst achieved a high selectivity of 89 % towards CO and a remarkable turnover number (TON) of 7991 during 8 h of visible light irradiation under CO2 in the presence of phenol as a co-substrate. The turnover frequency (TOF) in the initial 6 h was 1079 h-1, with an apparent quantum yield (AQY) of 1.08 %. Controlled experiments confirmed the dependency on the catalyst, light, and sacrificial electron donor for the CO2 reduction process. These findings demonstrate this bioinspired nickel molecular catalyst could be effective for fast and efficient photochemical catalytic reduction of CO2 to CO.