Lewis functional nanodiamonds for efficient metal-free photocatalytic CO2 reduction

Abstract

Artificial photosynthesis of fuels and valuable compounds from CO2 and H2O, as a flawless method, has aroused universal interest. Metal-free catalytic materials with balanced efficiency and stability have rarely been demonstrated. Up to date, emerging carbon-based photocatalysts promise to break the ordeal of extreme environments for catalysts, leading to practical industrial applications. Among them, surface functional group-modified nanodiamonds offer additional possibilities in terms of long-time stability and tunable catalytic activity. In this work, the nature of distinctions in photocatalytic efficacy induced by two varieties of NDs modified with distinct Lewis acid-base functional groups was also systematically investigated. Furthermore, by using a bottom-up approach, amino and carboxyl as typical Lewis acids-bases groups modified nanodiamond (ND)-embedded three-dimensional g-C3N4 (3D CN) are demonstrated to be an impressive metal-free photocatalyst for photosynthetic production of CO. Combining in-situ photoelectrochemical analysis and density functional theory, the mechanism of heterojunction formation between 3D CN and ND modified with different functional groups was elucidated from kinetic and thermodynamic perspectives. The synergistic CO production rate of amino-modified NDs was found to be roughly 1.97 times higher than that of carboxyl-modified NDs. This pioneering work introduces the promising sp3-hybridized ND materials into the photoreduction CO2 systems in terms of surface chemistry, helping to enlighten an improved understanding of this emerging carbon material.