A wide range of CO : H2 syngas ratios enabled by a tellurization-induced amorphous telluride-palladium surface

The direct production of syngas via the electrochemical CO2 reduction reaction (CO2RR) is a process with high potential due to its environmentally-friendliness and product adjustability properties. However, it is challenging to synthesize syngas with a wide range of tunable CO/H-2 ratios. Herein, we report that introducing tellurium (Te) can change the crystallinity of a palladium (Pd) surface, providing a unique amorphous surface to achieve a wide range of CO/H-2 ratios from 0.27 to 5.37. Compared with a highly crystalline Pd surface, the amorphous Te-Pd surface significantly increases the CO faradaic efficiency (FE), yet decreases the H-2 FE, leading to continuously tunable syngas. Detailed characterization shows that the surface tellurization of Pd nanoparticles (NPs) enhances the CO2 adsorption yet weakens the adsorption of COOH*, CO* and H* intermediates. Theoretical calculations further reveal that the amorphous Te-Pd surface shows a much lower barrier for the rate-determining step for CO* desorption, thus promoting CO generation. This work highlights the importance of the surface phase modification of metal electrocatalysts for the advanced CO2RR.