Rapid Fabrication of Metal-Nitrogen Doped Ordered Large-Pore Mesoporous Carbons Using Bottle Brush Block Copolymer Templates for Highly Efficient Water Oxidation
Authors: Saha Dipankar , Yu Hsin-Jung , Prateek * , Senger Claire , Pagaduan James Nicolas , Katsumata Reika , Carter Kenneth R. , Wu Nianqiang , Watkins James J. 
Published: September 2023

We describe a simple and fast method to fabricate ordered mesoporous carbon materials for electrocatalyst applications. Over the past decades, mesoporous carbons have been widely applied for photonics, energy storage devices, separation technologies, and electrocatalyst applications.1 These materials can be inexpensively prepared and have good electrical conductivity and chemical and mechanical stability. Linear block copolymer templates or polystyrene beads are widely used to create porosity in carbon materials. However, the existing methods have limitations in accessing a wide range of pore dimensions and porosities. Recently bottlebrush block copolymer (BBCP) templates have drawn significant attention for producing ordered carbon materials with ordered pores with tunable diameters ranging from 15 to 100 nm, which facilitates ion diffusion and mass transport during the electrochemical processes while maintaining high surface area.2

BBCP-derived large-pore mesoporous carbons are potential candidates for electrocatalyst applications. While water splitting produces hydrogen gas, oxygen gas simultaneously evolves via an oxygen evolution reaction (OER) or water oxidation.3 In OER, oxygen-oxygen bond formation involves a complicated proton-coupled mechanism. For this reason, most OER electrocatalysts require a high overpotential to overcome the sluggish kinetic energy barrier to generate oxygen gas during water oxidation, which is often associated with high costs and poor availability.4 Hence, developing a low-cost, highly efficient OER catalyst is necessary to lower the overpotential.

Herein, we demonstrate efficient metal-nitrogen-doped mesoporous carbon materials using a simple and fast rapid thermal annealing (RTA) process. BBCP/precursor self-assembly, carbonization and template removal using the RTA process (high heating rate up to 100 °C / sec) occurred within a few minutes. The resulting electrocatalysts were characterized by small-angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. We used nickel foam as a support under basic conditions for electrochemical evaluation. The results showed ample catalytic active sites and an overpotential of <260 mV along with a low Tafel value of 55 mV/decade at a current density of 10 mA/cm2. Our findings can have significant implications for designing various metal-doped mesoporous carbon materials for energy and environmental applications, specifically metal-air batteries and CO2 reduction.

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