# Enhanced ORR Activity of Modified Recycled Graphite-Based Anode Materials

## TL;DR

This paper shows how to recycle old battery graphite into a metal-free catalyst for oxygen reduction reactions, improving energy device efficiency.

## Contribution

A circular-economy strategy is introduced to upcycle spent lithium-ion battery graphite into a tunable, metal-free ORR catalyst.

## Key findings

- Acid activation of graphite increases defect density and ORR activity, achieving a half-wave potential of 0.782 V.
- Functionalization with NDI-ASP improves kinetic current density and charge-transfer characteristics compared to acid-treated graphite.
- XPS and SEM/EDX confirm successful incorporation of nitrogen- and phosphorus-containing species on the graphite surface.

## Abstract

Addressing the kinetic limitations of the oxygen reduction
reaction
(ORR) is essential for improving the efficiency of electrochemical
energy-conversion devices such as fuel cells and metal–air
batteries. Here, we demonstrate a circular-economy–oriented
upcycling strategy for transforming end-of-life lithium-ion battery
graphite anodes into metal-free ORR catalysts through oxidative activation
and targeted molecular functionalization. Spent graphite anode material
was activated by using H2SO4/HNO3 mixtures to increase defect density and surface reactivity, followed
by surface functionalization with BPDI-OH-Cl, NDI-alendronic acid
(NDI-ALEN), and NDI-aspartic acid (NDI-ASP). Acid activation significantly
enhanced apparent ORR activity, yielding the highest half-wave potential
(0.782 V for the 8 M acid-treated material), attributed to increased
defect density and improved electrolyte accessibility. Subsequent
molecular functionalization selectively modulated ORR behavior by
introducing heteroatom-containing surface species, with NDI-ASP functionalization
enhancing kinetic current density and charge-transfer characteristics
relative to acid-treated graphite, although the half-wave potential
remained slightly lower. XPS and SEM/EDX analyses confirm surface-confined
incorporation of nitrogen- and phosphorus-containing molecular species
following functionalization. These findings demonstrate that recycled
graphite can serve as a chemically tunable, metal-free ORR catalyst
platform, where defect generation governs apparent activity while
molecular functionalization modulates kinetic behavior and effective
electron-transfer characteristics, supporting circular-economy strategies
for sustainable electrochemical energy conversion.