Fabrication And Application Of Nanoporous Metal Catalysts For Fuel Cell

The gradual depletion of non-renewable energy has made people pay more and more attention to the development and application of new generation energy devices.Energy batteries represented by fuel cells are expected to completely solve people’s dependence on fossil energy and environmental pollution in the future.The main reason why fuel cells have not yet been commercialized on a large scale is that the cost and battery performance are lower than theoretical expectations.Carbon-supported Pt and precious metal catalysts are expensive and limited in resources,and long-term operation accompanied by corrosion of the carbon support limits the large-scale application of fuel cells.Nano-porous metal（NP-M）prepared by dealloying method is a free-standing functional catalytic material composed of nano-scale pores and ligaments intertwined in three-dimensional space.The main difference from traditional supported nanoparticle catalysts is NP-M not only provides a pore structure that is conducive to mass transmission,but also the abundant different coordinated atoms on the surface of the ligament makes nanoporous metals have excellent catalytic activity and long-range stability,so they are widely used in a variety of heterogeneous catalytic systems.The nanoporous metal catalyst can form a thin catalytic layer without use support materials,especially carbon materials.The porous and open nature of unsupported catalysts can provide sufficient active sites.This article uses free-standing nanoporous metal as a benchmark material and prepares NP-Pt Ru catalyst for methanol electrooxidation and anode catalyst layer in direct methanol fuel cell.At the same time,according to the characteristics of Ag in alkaline system,prepare NP-Ag Cu oxygen reduction catalyst and applied to the air cathode of zinc-air battery.The specific research mainly includes the following aspects:（1）The free-standing NPG-Pt Ru methanol oxidation electrocatalyst was prepared using nanoporous gold（NPG）as the base material.By controlling the ratio of Pt Ru,loading,and annealing temperature to explore the electrochemical performance of its methanol electrooxidation by different variables.The electrochemical test experiment shows that NPG-Pt₂Ru₁ has the highest active area of 86.9 m²/g,and has higher activity in methanol electrooxidation,with MA of 1.59 A/mg_pt and SA of 1.83 m A/cm²,respectively it is 2.1 and 1.42 times of commercial Pt Ru/C,4.52 and 1.96 times of commercial Pt/C,which has better stability at 130℃.（2）By using NPG-Pt₂Ru₁ as the anode catalyst layer in direct methanol fuel cell,the battery performance such as power density in a single cell was tested.Since the catalytic layer is only a few hundred nanometers thick and attached to the proton exchange membrane tightly,the methanol crossover experiment shows that this type of catalytic layer has lower methanol permeability at different temperatures than the commercial Pt Ru/C catalytic layer.The methanol stripping voltammetry experiment shows that the oxidation performance of methanol in the electrode increases with the increase of temperature.The discharge polarization curve results show that the ultra-thin NPG-Pt Ru catalyst has a Pt loading of 210μg/cm² at the anode,methanol concentration of 1 mol/L,and working temperature of 90℃.The power density of 145 m W/cm² is 65%higher than the high load capacity（Pt load 2 mg/cm²）under the same conditions.This is currently known to have the highest power performance when anode using low-load Pt at 90℃.（3）The nanoporous Ag Cu electrocatalyst with trace Cu content was designed and prepared by the dealloying method.The alkaline oxygen reduction test showed that Cu doping improves the oxygen reduction performance of NP-Ag.Among them,The SA of NP-Ag₄Cu is 0.353 m A/cm²,which is about 9 times higher than NP-Ag and 80%higher than commercial Pt/C.And in the zinc-air battery test,the maximum power density of using NP-Ag₄Cu as the air electrode catalyst is 151.5 m W/cm²,which is greater promote than the performance of using NP-Ag（83.8 m W/cm²）as the air electrode.The nanoporous structure builds a smooth channel for electron conduction and mass transfer,proving that dealloying strategy has great application potential in the development of high-performance electrochemical energy devices...