Decrypting the Controlled Product Selectivity over Tunable Ni─Co Bimetallic Alloy for Photoreduction CO2

Abstract

Efficiently regulating reaction pathways for photoreduction CO₂ to achieve required products is enormously strenuous. The design of active sites for CO₂ adsorption, activation, and tuning of reaction pathways is pivotal to address this grand challenge. Herein, highly selective sites are developed for photoreduction CO₂ to HCOOH and CO based on asymmetrically coupling different ratios of Ni and Co loaded on crystalline carbon nitride (CCN) by an alloying synthesis strategy, which is confirmed by high-resolution transmission electron microscopy (HRTEM) imaging, X-ray diffraction (XRD) patterns, and X-ray photoelectron spectroscopy (XPS) spectra. In situ Fourier transform infrared spectra suggest that the key intermediate *OCHO to HCOOH pathway prefers to form on Ni sites, while *COOH to CO pathway tends to generate on Co sites, and the characteristic peaks intensity of the two key intermediates are stronger with the synergistic effects of NiCo bimetallic, further verified by the theory calculations. Accordingly, HCOOH with a selectivity of 98.5% (194.5 µmol g⁻¹ h⁻¹) or CO with a selectivity of 85.4% (144.8 µmol g⁻¹ h⁻¹) can be achieved on the optimized Ni_xCo_y alloy, under sacrificial agent-free conditions.