Rational Design of Sulfur‐Doped Copper Catalysts for the Selective Electroreduction of Carbon Dioxide to Formate

Abstract

The selective electroreduction of CO2 to formate (or formic acid) is of great interest in the field of renewable‐energy utilization. In this work, we designed a sulfur‐doped Cu2O‐derived Cu catalyst and showed that the presence of sulfur can tune the selectivity of Cu significantly from the production of various CO2 reduction products to almost exclusively formate. Sulfur is doped into the Cu catalysts by dipping the Cu substrates into ammonium polysulfide solutions. Catalyst films with the highest sulfur content of 2.7 at % showed the largest formate current density (jHCOO- ) of −13.9 mA cm−2 at −0.9 V versus the reversible hydrogen electrode (RHE), which is approximately 46 times larger than that previously reported for Cu(110) surfaces. At −0.8 V versus RHE, the faradaic efficiency of formate was maintained at approximately 75 % for 12 h of continuous electrolysis. Through the analysis of the evolution of the jHCOO- and jnormalH2 values with the sulfur content, we show that sulfur doping increases formate production and suppresses the hydrogen evolution reaction. Ag–S and Cu–Se catalysts did not exhibit any significant enhancement towards the reduction of CO2 to formate. This demonstrates clearly that sulfur and copper acted synergistically to promote the selective formation of formate. A hypothesis about the role of sulfur is proposed and discussed.

Tuning Sn-Cu Catalysis for Electrochemical Reduction of CO2 on Partially Reduced Oxides SnOx-CuOx-Modified Cu Electrodes

“…However, there are still many problems to be addressed, such as competition with hydrogen evolution reaction (HER) and low selectivity towards a desired product. Experimental and theoretical studies have revealed that the selectivity of Cu can be tuned by introducing a secondary component, such as indium (In), tin (Sn) and sulfur (S) [11][12][13][14].…”

Nitride‐Derived Copper Modified with Indium as a Selective and Highly Stable Catalyst for the Electroreduction of Carbon Dioxide

“…[2] The emergence of synergistic effects in multicomponent systems provides unique opportunities to overcome the scaling relation [3,4] between the binding energieso fi ntermediates inherently limiting the performance of transition metals typically used for this reaction. [5,6] However, al imited understanding of interfacial effects frequently accompanied by deep compositional and/or structural changes under reactionc onditions [7][8][9][10][11] precludes the derivationo fa ccurate structure-performancer elationships that can guide the optimization toward breakthrough advances.…”

Electrochemically Driven Cation Exchange Enables the Rational Design of Active CO2Reduction Electrocatalysts

“…As the amount of passed charge increases, CoS x phase reconstruction by ED‐CE with Cu ions further proceeds, as evidenced by the gradually attenuated Raman signals (Figure b) at 680, 612, 518, and 192 cm −1 , corresponding to CoO x and Co(OH) 2 (air oxidized CoS x ) . The broad Raman peak at 240–400 cm −1 , previously assigned to the vibrational mode of metal–S stretching (≈352 cm −1 for Co−S in CoS 2 and ≈296 cm −1 for Cu−S in Cu 2 S), remains but exhibits a slight redshift, suggesting the weakening of Co−S bonds in the CoS x templates, and further indicating the gradual replacement of Co ions in the CoS x matrix by the Cu 2+ ions in solution …”