Boosting Neutral Water Oxidation through Surface Oxygen Modulation

Abstract

Developing efficient electrocatalysts for oxygen evolution reaction (OER) in pH‐neutral electrolyte is crucial for microbial electrolysis cells and electrochemical CO2 reduction. Unfortunately, the OER kinetics in neutral electrolyte is sluggish due to the low concentration of adsorbed reactants, with overpotentials of neutral OER at present much higher than that in acidic or alkaline electrolyte. Here, hydrated metal cations (Ca2+) are sought to be incorporated into the state‐of‐the‐art Ru–Ir binary oxide to tailor the surface oxygen environments (lattice‐oxygen and adsorbed oxygen species) for efficient neutral OER. Using a sol–gel method, ternary Ru–Ir–Ca oxides are synthesized in atomically homogenous manner, and the obtained catalyst on glassy carbon electrode achieves 10 mA cm−2 at a low overpotential of 250 mV, with no degradation for 200 h of operation. In situ X‐ray absorption spectroscopy, in situ 18O isotope‐labeling differential electrochemical mass spectrometry, and 18O isotope‐labeling secondary ion mass spectroscopy studies are carried out. The results reveal that incorporation of Ca2+ can enhance the covalency of metal–oxygen bonds and the electrophilic nature of surface metal‐bonded oxygen sites; and simultaneously facilitate the adsorption of water molecules on catalyst surface, which accelerates the lattice‐oxygen‐involved reaction, thus improving the overall OER performance of RuIrCaOx catalyst.

Iridium‐cobalt alloy nanotubes as a bifunctional electrocatalyst for pH‐universal overall water splitting

“…The Tafel slopes and overpotentials of as‐prepared nanomaterials were generally larger in neutral condition than the corresponding values measured in alkaline and acidic media. This indicates more sluggish OER kinetics in neutral media as previously reported 31 …”

Ar/H2/O2‐Controlled Growth Thermodynamics and Kinetics to Create Zero‐, One‐, and Two‐Dimensional Ruthenium Nanocrystals towards Acidic Overall Water Splitting

“…[ 1–8 ] The development of excellent electrocatalysts is the key to improve the performance of the water splitting reaction by accelerating the reaction kinetics of both the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). [ 9–16 ] Among the various excellent electrocatalysts, Ru and its oxide‐based catalysts have shown great potentials in the HER and OER fields, respectively, because they have suitable binding energies of hydrogen and oxygen, respectively. [ 17–24 ]…”

Self-supported Cu3P nanowire electrode as an efficient electrocatalyst for the oxygen evolution reaction

“…Electrochemical impedance spectrum (EIS) was conducted to explore the electrode kinetics. 47,48 As depicted in Fig. 5d and Table S2, † Cu 3 P NWs/CF has a much smaller charge-transfer resistance (3.6 ohm) than RuO 2 /CF (4.5 ohm), Cu 3 P/CF (9.5 ohm), and Cu foam (14.4 ohm), implying a fast charge transfer process of Cu 3 P NWs/CF.…”