Stable and Highly Efficient Electrochemical Production of Formic Acid from Carbon Dioxide Using Diamond Electrodes

Abstract

High faradaic efficiencies can be achieved in the production of formic acid (HCOOH) by metal electrodes, such as Sn or Pb, in the electrochemical reduction of carbon dioxide (CO ). However, the stability and environmental load in using them are problematic. The electrochemical reduction of CO to HCOOH was investigated in a flow cell using boron-doped diamond (BDD) electrodes. BDD electrodes have superior electrochemical properties to metal electrodes, and, moreover, are highly durable. The faradaic efficiency for the production of HCOOH was as high as 94.7 %. Furthermore, the selectivity for the production of HCOOH was more than 99 %. The rate of the production was increased to 473 μmol m s at a current density of 15 mA cm with a faradaic efficiency of 61 %. The faradaic efficiency and the production rate are almost the same as or larger than those achieved using Sn and Pb electrodes. Furthermore, the stability of the BDD electrodes was confirmed by 24 h operation.

Nanodiamonds for energy

“…The selectivity of formate formation from CO 2 reached 99% with BDD as the electrode in a flow cell; the production of formate is 473 µmol m −2 s −1 at a current density of 15 mA cm −2 with a faradic efficiency of 61%. In addition, the BDD has no obvious decay after 24 hours of operation . Furthermore, the formation of a CO side product slightly increases with increased doping of boron, suggesting the binding energy of CO 2 and its intermediates could be altered by doping levels .…”

“…Applications of nanodiamonds on energy‐related fields (eg, supercapacitor, battery, electrocatalysis, optoelectronic, thermoelectronic, nanofluids, and water treatment)…”

A Disquisition on the Active Sites of Heterogeneous Catalysts for Electrochemical Reduction of CO2 to Value‐Added Chemicals and Fuel

“…However, the typical production rate reported with these BDD catalysts are low, bringing questions about the suitability of these electrocatalysts for large scale application. To improve the low production rate, a circulation flow cell system was also adopted with BDD catalyst . It can be observed from Figure 20 that the BDD can successfully generate formic acid with a very high FE HCOO − of 95% (Figure a) and a large production rate of 473 µmol m −2 s −1 (Figure b) with prominent stability (Figure c,d).…”

“…c) Faradaic efficiency and d) concentration of HCOOH by the electrochemical reduction of CO 2 with a BDD electrode at an applied current of 2 mA cm −2 and a flow rate of 200 mL min −1 . Reproduced with permission . Copyright 2018, Willey‐VCH.…”

Composition Tailoring via N and S Co‐doping and Structure Tuning by Constructing Hierarchical Pores: Metal‐Free Catalysts for High‐Performance Electrochemical Reduction of CO2

“…[21] TheT afel slope of 159, 192, and 132 mV dec À1 indicated the poor kinetics on NSHCF800, NSHCF1000, and NSCF900. [18][19][20][21][22][23][24][25] In our study,N-doped hierarchically porous carbon nanofiber (NHCF900;S upporting Information, Figure S15) only yields 63 %F aradaic efficiencyfor CO in CO 2 RR, which is significantly lower than that of NSHCF900, signifying the importance of Ss pecies.T he relationship between the nitrogen and sulfur contents in catalysts and the associated CO 2 RR activity is illustrated in the Supporting Information, Figure S16, which demonstrates that pyridinic Ni st he dominant active sites for CO 2 RR, and the presence of carbon-bonded Sc an greatly enhance the catalytic activity. [20,31] We hypothesize that the doped species within NSHCF is the origin of the disparity in the catalytic activity (for example,N -doped carbons have excellent CO 2 RR capabilities).…”