The chemical inertness
of polyethylene makes chemical recycling
challenging and motivates the development of new catalytic innovations
to mitigate polymer waste. Current chemical recycling methods yield
a complex mixture of liquid products, which is challenging to utilize
in subsequent processes. Here, we present an oxidative depolymerization
step utilizing diluted nitric acid to convert polyethylene into organic
acids (40% organic acid yield), which can be coupled to a photo- or
electrocatalytic decarboxylation reaction to produce hydrocarbons
(individual hydrocarbon yields of 3 and 20%, respectively) with H
2
and CO
2
as gaseous byproducts. The integrated
tandem process allows for the direct conversion of polyethylene into
gaseous hydrocarbon products with an overall hydrocarbon yield of
1.0% for the oxidative/photocatalytic route and 7.6% for the oxidative/electrolytic
route. The product selectivity is tunable with photocatalysis using
TiO
2
or carbon nitride, yielding alkanes (ethane and propane),
whereas electrocatalysis on carbon electrodes produces alkenes (ethylene
and propylene). This two-step recycling process of plastics can use
sunlight or renewable electricity to convert polyethylene into valuable,
easily separable, gaseous platform chemicals.