Preparation Of Core-shell Structure Carbon-based Active Support For Water Oxidation Reaction

The process of electrolyzing water is divided into two parts:Hydrogen evolution reaction?HER?on the cathode and Oxygen evolution reaction?OER?on the anode.In the water decomposition reaction,the oxygen evolution reaction?OER?needs to transfer more electrons than the hydrogen evolution reaction?HER?,which is the reaction control step.The process of OER involves the transfer of four electron-proton.This reaction is a chemical reaction process with a high overpotential in both thermodynamics and kinetics.Because OER requires high energy to overcome kinetic barrier to occur,high-efficiency electrocatalysts are necessary to reduce overpotential and thus improve the energy efficiency of OER.One of the main challenges in achieving hydrogen production from electrolyzed water is to find a stable and efficient OER catalyst.Since the support of conventional electrocatalysts is mostly inert,certain parts of these supported electrocatalysts that have direct contact with the reactants do not have electrocatalytic function.Therefore,the BET surface area of these electrocatalyst is larger than their electrochemically active surface area.So as to make full use of the available surface area and release the activity potential of the electrocatalysts,this work synthesized a carbon-based active support with certain electrocatalytic activity for water oxidation reaction,the originally inert and idle positions of the catalyst are now replaced by active sites integrated with carbon,leading to the electrochemically active surface area closer to its surface area.This carbon-based active support is prepared by carbonizing its precursor composed of Prussian blue analogs nanoframes?PBA-NF?,fibrous silica?f-SiO₂?and aminophenol-formaldehyde resin?APF?in order from the inside to the outside.PBA-NF was originally used as a supporting frame for the entire material and was converted into CoFe-nanoparticles?NPs?with certain electrocatalytic activity after carbonization.After carbonization,APF can be converted into ordered mesoporous carbon?OMC?with good electrical conductivity,low electrical resistance,and ideal surface area,while f-SiO₂ can adjust the roughness of the carbon layer surface,thereby changing the capacity of the support.In detail,a cubic core-shell support was synthesized via an aqueous phase synthesis method for oxygen evolution reaction.The carbon-based active support with a larger specific surface area(306 m² g^-1)is beneficial to the dispersion of the active sites.The support has appropriate OER catalytic activity which can synergistically catalyze OER together with Ni₉Fe?oxy?hydroxide loaded onto it.Under the current density of 10 mA cm^-2,the overpotential is as low as 214 mV for OER,which is better than those of most non-precious metal catalysts,suggesting that carbon-based active support could effectively reduce energy consumption via promoting surface area utilization ratio.This work provides a general route to release the activity potential of the electrocatalysts and prepare supported electrocatalysts with electrochemically active surface area close to their surface area.