Although hydrogen fuel is a promising alternative to fossil fuels, its power generation relies on catalysts mainly composed of the rare and expensive metal platinum, which limits its widespread commercialization. UCLA researchers report a method, a technique with high catalyst performance, high stability, and low platinum usage.
The record-breaking technique uses tiny crystals of a platinum-cobalt alloy, each embedded in nanopockets made of graphene.
Compared to the DOE catalyst standard, the graphene-wrapped alloy produced extraordinary results: 75 times higher catalytic activity; 65% higher power; approximately 20% higher catalytic activity at the end of the expected fuel cell life; 6000-7000 hours of simulated use Since then, power losses have been reduced by about 35%, surpassing the 5,000-hour target for the first time; almost 40% less platinum is required per car.
Today, half of the world's total supply of platinum and similar metals is used in catalytic converters in fossil-fuel-powered cars, a component that reduces the harmfulness of their emissions. Each car requires 2-8 grams of platinum. By comparison, current hydrogen fuel cell technology consumes about 36 grams of platinum per vehicle. At the lowest platinum load the research team tested, only 6.8 grams of platinum were needed per hydrogen-powered car.
The researchers broke down the platinum-based catalyst into particles that were on average 3 nanometers long. Smaller particles mean more surface area, which also means more space for catalytic activity to occur. However, smaller particles tend to crowd together to form larger particles.
The research team addressed this limitation by loading their catalyst particles in the 2D material graphene. Compared to the bulk carbon commonly found in coal or pencil lead, this thin layer of carbon has a surprising capacity to conduct electricity and conduct heat efficiently and is 100 times stronger than steel of similar thickness.
Their platinum-cobalt alloy is reduced to particles. Before being integrated into a fuel cell, the particles are surrounded by graphene nanopouches that also act as an anchor to prevent particle migration, which is required for the level of durability required for commercial vehicles. At the same time, graphene allows tiny gaps of about 1 nanometer around each catalyst nanoparticle, which means that critical electrochemical reactions can take place.
