Metal–Organic Framework‐Based Nanomaterials for Electrocatalytic Oxygen Evolution

Abstract

tion scale and sustainability. [1] The overall water splitting involves a pair of electrochemical reactions occurring at two separate electrodes, that is, the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. [2] In comparison to HER, OER involving four-electron transfer not only possesses a large thermodynamic potential but also leads to serious sluggish kinetics. [3] Thus, it is highly desirable to develop efficient OER catalysts for realizing the large-scale production and widespread use of hydrogen.Noble metal oxides (e.g., IrO 2 and RuO 2 ) have long been regarded as the best OER catalysts due to their high activity. [4] However, the scarcity of these Ir/Ru-based materials results in the cost greatly increases, which seriously hinders their industrial application. [5] Besides, the adsorption of noble metal-based catalysts to oxygen-containing intermediates is relatively strong so that the active sites are easily blocked, leading to their catalytic activity being degraded dramatically. In the past years, a variety of transition metal-based materials have been developed as efficient and cost-effective catalysts for OER. Compared with the traditional metal oxides/hydroxides, nitrides, sulfides, and phosphides, metal-organic framework (MOF)-based materials possess many special advantages in activity improvement and optimization, mass transfer and diffusion, as well as structure-performance relation exploration. For example, MOFs are linked by coordination bonds between organic ligands and metal nodes with periodic structural units, which provides an ideal platform for fundamental catalytic mechanism study. The metal interaction for catalytic performance improvement can be quantitatively presented by precisely controlling the atom species and ratio in MOFs. [6] In addition, the design of ligands in length and coordination atom of MOFs could not only optimize the electron distribution of active sites but also achieve the precise regulation of the pore sizes and surface areas. Apart from the intrinsic design for pure MOFs, composition and functionalization can further improve their physicochemical properties, such as conductivity and wettability, leading to the catalytic activity and stability further boosted during electrocatalysis. [7] Substantial efforts recently have been made to fabricate high-performance catalysts for electrocatalysis by employing MOFs as pyrolytic precursors/ templates. [8] During pyrolysis, the organic carbon framework will be converted into inorganic carbon, and metals can be in Oxygen evolution reaction (OER) is an energy-determined half-reaction for water splitting and many other energy conversion processes, such as rechargeable metal-air batteries and CO 2 reduction, due to its four-electron sluggish process. To reduce the energy consumption and cost of these advanced technologies, various transition metal-based nanomaterials, like metal oxides/hydroxides, nitride, and phosphide are synthesized. Among these, metal-organic framework (...

Three-dimensional porphyrin-based covalent organic frameworks withstptopology for an efficient electrocatalytic oxygen evolution reaction

“…The key to developing efficient electrocatalysts has always been the precise design of the metal catalytic centres. [49][50][51][52] As is known, metalloporphyrins, especially Co-embedded porphyrins, have been demonstrated to be effective electrocatalytic oxygen evolution reaction (OER) catalysts. 29,53,54 As a new metallizable porphyrin-based 3D-COF, ZJUT-1 is expected to generate abundant and accessible catalytic active centers after embedding cobalt ions into COF pore walls and thus achieve efficient OER catalytic activity.…”

Accelerating Electrochemical Water Oxidation Activity by Tailoring Morphology and Electronic Structure of Nickel Organic Framework Nanoarrays with a Fe Etching Effect

“…From their LSV curves of NiFe-NDC NAs with different content of Fe in Figure S8, NiFe-NDC NAs-2 (2 mg FeSO 4 ·7H 2 O) showed the optimist performance, which could be attributed to the most exposed actives of Ni­(III) with modulated squamous nanostructures by the Fe etching effect. The high-valence and high-proportion Ni­(III) was closely related to the activity of water oxidation. − The kinetic of all materials were subsequently evaluated by the Tafel slope (Figure b). As expected, NiFe-NDC NAs possessed the smallest Tafel slope (57.3 mV dec –1 ) among them, while Ni-NDC NAs showed an even larger value at 121.5 mV dec –1 than Ni­(OH) NAs (87.9 mV dec –1 ), letting alone commercial RuO 2 (69.5 mV dec –1 ).…”

Oxygen Evolution Reaction by Silicate-Stabilized Manganese Oxide

“…In addition to previously reported strategies, − this study investigated silicate-stabilized Mn oxide under acidic conditions (H 2 SO 4 (0.10 M)) toward OER. After chronoamperometry at 2.05 V for 4 h, a significant decrease (72%) was observed in the current density of prepared Mn oxide in the absence of Na 2 SiO 3 .…”