Self‐Assembly of Large‐Area 2D Polycrystalline Transition Metal Carbides for Hydrogen Electrocatalysis

Abstract

hydrogen evolution using sustainably produced electricity has promised a carbonfree production of a chemical fuel. [5] However, most commercial hydrogen is still produced via steam reforming of methane because there are few scalable base-metal replacements for platinum at the scales required for electrocatalysis. [6] Dimensional reduction of 3D materials to 0D, 1D, or 2D nanostructures (thickness vs lateral size < 1%), [7,8] has attracted interest for discovering intriguing new catalytic properties. Notably, including 2D nanostructures comprised of metals, [9] transition metal dichalcogenides, [10][11][12] transition metal oxides, [13,14] and 2D transition metal carbides (TMCs) [15] have been explored for enhanced catalytic performance, and advances in this area have led to reliable and cost-effective fabrication methods ideal for base-metal hydrogen evolution catalysts.Among these materials, 2D TMCs possess excellent electrical conductivity, electrochemical activity, high surface area, and strong chemical resilience. [16] These make them particularly desirable for various clean energy applications such as energy storage [17][18][19] and catalysis. [7,15] The most widely applied method toward 2D TMCs requires a selective etching process from their Low-dimensional (0/1/2 dimension) transition metal carbides (TMCs) possess intriguing electrical, mechanical, and electrochemical properties, and they serve as convenient supports for transition metal catalysts. Large-area single-crystalline 2D TMC sheets are generally prepared by exfoliating MXene sheets from MAX phases. Here, a versatile bottom-up method is reported for preparing ultrathin TMC sheets (≈10 nm in thickness and >100 μm in lateral size) with metal nanoparticle decoration. A gelatin hydrogel is employed as a scaffold to coordinate metal ions (Mo 5+ , W 6+ , Co 2+ ), resulting in ultrathin-film morphologies of diverse TMC sheets. Carbonization of the scaffold at 600 °C presents a facile route to the corresponding MoC x , WC x , CoC x , and to metal-rich hybrids (Mo 2−x W x C and W/Mo 2 C-Co). Among these materials, the Mo 2 C-Co hybrid provides excellent hydrogen evolution reaction (HER) efficiency (Tafel slope of 39 mV dec −1 and 48 mV j = 10 mA cm −2 in overpotential in 0.5 m H 2 SO 4 ). Such performance makes Mo 2 C-Co a viable noble-metal-free catalyst for the HER, and is competitive with the standard platinum on carbon support. This template-assisted, self-assembling, scalable, and low-cost manufacturing process presents a new tactic to construct low-dimensional TMCs with applications in various cleanenergy-related fields. Hydrogen ElectrocatalysisThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Fast Gelation of Ti3C2Tx MXene Initiated by Metal Ions

“…MXene is a new type of 2D materials that have attracted great interest due to its unique properties and great potential for use in different energy storage devices . However, because of the random restacking of the MXene nanosheets (NSs) there is a loss of accessible surface area and an increase of ion diffusion resistance that greatly lower their electrochemical performance.…”

A Highly Stretchable Microsupercapacitor Using Laser‐Induced Graphene/NiO/Co3O4 Electrodes on a Biodegradable Waterborne Polyurethane Substrate

“…[28] The transparency of a logo pattern induced on the PI film and then transferred to the WPU substrate is shown in Figure 1b, which also indicates the convenience and universality of our stretchable MSC fabrication method. [40,41] More importantly, the high-magnification image in Figure 1e reveals that LIG is decorated evenly with small round convex particles, indicating a portion of the hybrid NiO/Co 3 O 4 nanoparticles were distributed on surface. [12,15] While in situ synthesized NiO/Co 3 O 4 /LIG shows a completely different morphology (Figure 1d) in that the entire structure is composed of multilayer graphene, which is a synergistic result of the simultaneous carbonization of PI and gelatin.…”

“…[37] Second, stretchable MSCs assembled on PDMS and silicone rubber, which cannot be degraded under natural conditions, pose a potential threat to the living environment. [40][41][42] It was found that the gelatin could modify the surface morphology and wettability of NiO/ Co 3 O 4 /LIG. [39] In this work, a gelatin-mediated ink containing Ni and Co ions was coated onto a PI film and subjected to laser direct writing, during which the gelatin was completely cocarbonized with PI while in situ synthesizing laser-induced graphene/NiO/ Co 3 O 4 (NiO/Co 3 O 4 /LIG).…”

High‐Voltage Supercapacitors Based on Aqueous Electrolytes

“…Neutral electrolytes could result in high operation voltages as compared with those in acidic and alkaline electrolytes by reducing the possibility of inducing the water hydrolysis reaction due to either the hydrogen evolution reaction (HER) or oxygen evolution reaction (OER) ,,. Furthermore, materials with low absorption energy of hydrogen or oxygen are generally good catalysts for HER and OER . Meanwhile, materials with poor catalytic efficiency such as carbon‐based materials have high overpotentials.…”