Boosting efficient C-N bonding toward photoelectrocatalytic urea synthesis from CO2 and nitrate via close Cu/Ti bimetallic sites

Abstract

The urea synthesis is limited by inefficiently C-N bonding from CO2 and nitrate. Here, we engineered dual metal Cu and Ti active sites with short distance by single atom Cu anchored on TiO2, which is conducive to C-N bonding for photoelectrocatalytic urea synthesis with CO2 and nitrate, achieving record-highest urea Faradic efficiency of 68%. The Cu site efficiently catalyzed reduction of CO2 to *CO, and adjacent Ti site catalyzed reduction of nitrate to *NH2 intermediate on SAC Cu-TiO2. The close Cu and Ti sites shorten distance between *CO and *NH2 intermediate for coupling, which is conducive to C-N bonding for photoelectrocatalytic synthesizing urea. DFT and in-situ FT-IR spectroscopy suggested that compared with their parallel competing reactions of *NH2 and *CO intermediates, coupling of *CO and *NH2 at close Cu and Ti sites had a lower energy barrier on SAC Cu-TiO2, which is an important reason for efficient synthesis of urea.