Enhanced solar urea synthesis from CO2 and nitrate waste via oxygen vacancy mediated-TiOx support lead-free perovskite

Abstract

The nitrogen fertilizer industry, particularly urea production, notably contributes to greenhouse gas emissions and energy consumption. Urea synthesis via solar energy encounters several challenges. Specifically, solar urea synthesis methods often exhibit low efficiency and yield, primarily stemming from inefficient energy conversion processes and intricate reaction pathways. Moreover, the kinetics of the urea synthesis reaction may be sluggish, thereby impacting the overall production rate. Therefore, in this study, we introduce a novel electron-reserve-enhanced Cs2CuBr4/TiOx-Ar (CCBT-Ar) structure for the photocatalytic synthesis of urea from CO2 and nitrate waste. Theoretical calculations and spectroscopic analysis underscore the critical role of oxygen vacancies (Ov) within the amorphous TiOx shell, enhancing reactant adsorption and catalyzing the rate-determining step (*OCONH2→*HOCONH2). However, the presence of Ov also results in significant carrier recombination, acting as trapping centers and reducing urea production activity. Importantly, we demonstrate that in-situ-grown carbon nanosheets, in conjunction with TiOx, function as efficient electron reservoirs, markedly mitigating trapping-induced recombination and facilitating electron redistribution. These reserved electrons can then actively participate in the urea synthesis process. As a result, the electron-reserve-enhanced structure exhibits robust solar urea yield and selectivity, even in challenging wastewater conditions. This work provides a rational and innovative approach to catalyst development in complex solar synthesis, offering promising avenues for the sustainable production of value-added chemicals while concurrently reducing carbon emissions.