Deciphering the Heterojunction Synergy of Bi Telluride Embellished with SnAl-LDH Microflowers for Highly Selective Photo-Electrochemical CO2 Reduction to Formic Acid

Abstract

The photoelectrochemical reduction reaction of CO2 (PEC–CO2RR) into value-added products presents a promising avenue for mitigating the climate crisis and addressing global energy demands. In the present study, a photocathode comprising a composite of Bi2Te3 as a transition metal chalcogenide and SnAl layered double hydroxide (LDH) microflowers was synthesized via a one-pot hydrothermal technique. The fabrication of the Type-II heterojunction of Bi2Te3/SnAl-LDH significantly accelerated photogenerated charge carrier separation and transportation, thereby markedly augmenting the PEC–CO2RR performance of the synthesized photoelectrocatalyst. Employing a photoassisted approach, the Bi2Te3/SnAl-LDH-15 wt % photocathode exhibited an excellent Faradaic efficiency of 97.2% for formic acid (HCOOH) production at −0.9 VRHE, accompanied by a high partial current density of ∼12 mA cm–2. The superior activity of the PEC catalyst was ascribed to its 3D core–shell architecture, wherein Bi2Te3 rods were uniformly decorated with SnAl-LDH microflowers, effectively suppressing charge recombination and enhancing charge transport. Furthermore, the Type-II heterojunction of Bi2Te3/SnAl-LDH-15 wt % facilitated stronger CO2 chemisorption and the ability to adsorb key intermediate species associated with HCOOH production. Tafel slope analysis showcased a significantly reduced value of 121.1 mV dec–1, indicative of enhanced PEC–CO2RR kinetics for HCOOH production. Turnover frequency (TOF) measurements were also conducted to evaluate the catalytic performance, wherein the hybrid composite exhibited a remarkable TOF of 0.61 s–1 at −1.0 VRHE. Moreover, it demonstrated a commendable energy efficiency of 67.5% at −0.9 VRHE, highlighting its potential for efficacious CO2 valorization.