Electrodeposition of Tin-Based Electrocatalysts with Different Surface Tin Species Distributions for Electrochemical Reduction of CO₂ to HCOOH

Abstract

Tin-based electrocatalysts with different tin species distributions were deposited on the carbon paper substrate by three electrodeposition methods and applied to the selective electroreduction of carbon dioxide to formic acid. Among them, the electrocatalysts prepared using unipolar pulse electrodeposition (UPED) method exhibited the maximum HCOOH faradaic efficiency of 89% at −1.7 V (vs Ag/AgCl) with a current density of 6.0 mA cm −2 and long-term stability in the 0.1 M CO 2saturated KHCO 3 solution. Moreover, the effects of surface oxides species on the performance of tin-based electrocatalysts were systematically investigated via density functional theory (DFT) calculations. The calculation results indicated that both metal tin and tin oxides had excellent catalytic ability for the electrochemical reduction of CO 2 to HCOOH. Specifically, the tetravalent tin (Sn 4+ ) and divalent tin (Sn 2+ ) species can reduce the overpotential and improve the HCOOH selectivity, respectively. In addition, we found that the tin oxides/metal tin interface can suppress the evolution of H 2 , but we observed no obvious effect on the formations of HCOOH and CO. Thus, the actual CO 2 catalytic electroreduction process should be synergistically controlled by the complex surface oxide species on the tin-based electrocatalysts.

Induced CO2 Electroreduction to Formic Acid on Metal−Organic Frameworks via Node Doping

“…[15] Bai et al found that alloying Sn to palladium reached nearly 100 % of FE HCOOH through an optimal surface PdÀ SnÀ O configuration at the lowest overpotential of À 0.26 V. [16] An et al revealed that the tetravalent tin and divalent tin species can reduce the overpotential and improve the HCOOH selectivity, respectively. [17] These findings witnessed the feasibilities and advantages of Sn species in CO 2 electrocatalytic reduction to HCOOH. However, integrating Sn into the node while preserving the whole framework well remains a challenge, and few study involve in ZIFs catalysts with Sn doping for CO 2 conversion.…”

“…Sn-based catalysts have been most frequently used to produce HCOOH in CO 2 ERR due to the tin intrinsic activity. [15][16][17] Lei et al reported that confined Sn in ultrathin graphene exhibited higher CO 2 electroreduction activities with a HCOOH FE of 85 % at À 0.48 V overpotential. [15] Bai et al found that alloying Sn to palladium reached nearly 100 % of FE HCOOH through an optimal surface PdÀ SnÀ O configuration at the lowest overpotential of À 0.26 V. [16] An et al revealed that the tetravalent tin and divalent tin species can reduce the overpotential and improve the HCOOH selectivity, respectively.…”

“…The Sn 3d spectra can be deconvoluted to three peak groups as Sn 0 (484.3 eV, 493.2 eV), Sn 2 + (486.4 eV, 495.1 eV), and Sn 4 + (487.8 eV, 496.4 eV), respectively (Figure 2A). [17,24] The detailed and quantitative tin compositions are shown in Table S4, and the Sn 3d 5/2 and Sn 3d 3/2 splitting peaks of xSZ catalysts are mainly assigned to Sn 2 + , more than 80 %, implying the equivalent substitution of Zn 2 + with Sn 2 + in the nodes of xSZ catalysts. Moreover, 0.6SZ shows the lowest Sn 0 / Sn total and Sn 2 + /Sn total ratios and the highest Sn 4 + /Sn total of 11.3 % compared to the other xSZ catalysts, implying the relatively high mismatching node structure in 0.6SZ.…”

“…This implies that the Sn doping facilitates the further conversion of CO 2 À to HCOOH. [15,17] The catalysts 0.6SZ and 0.8SZ possess the smallest R ct '' values of 9.7 and 9.5 Ω, which will significantly benefit the electroreduction of CO 2 .…”

Rh/Ce0.25Zr0.75O2 Catalyst for Steam Reforming of Propane at Low Temperature

“…Fuel cells can directly convert chemical energy into electrical energy more efficiently than internal‐combustion engines and have therefore attracted considerable attention as environmentally friendly power‐generation devices . Among the various types of fuel cells, solid oxide fuel cells (SOFCs) show the highest energy‐conversion efficiency and therefore emit less CO 2 than conventional combustion engines . However, the operation temperature of the currently available SOFC systems is so high (700–1000 °C) that starting and shutting them down is time‐consuming, and the component parts deteriorate readily.…”