# Scalable Defect Engineering of Pt3Te4 Nanosheets Activates an Electro-Switchable and Termination-Dependent PtO2 Skin for Low-Overpotential Hydrogen Evolution

## TL;DR

This paper shows how to create efficient hydrogen production catalysts using nanosheets of a topological metal, Pt3Te4, by engineering their surface chemistry.

## Contribution

The study introduces a scalable method to create electro-switchable PtO2 skins on Pt3Te4 nanosheets for enhanced hydrogen evolution.

## Key findings

- H2O2-assisted exfoliation creates nanoporous Pt3Te4 nanosheets with a bias-controlled PtO2 skin.
- PtO2 forms selectively on PtTe2-like terminations, improving HER performance with lower overpotential and higher current density.
- The catalytic activity is stable over 50 hours in acidic conditions with no change in Tafel slope.

## Abstract

Topological materials
are promising electrocatalysts for the hydrogen
evolution reaction (HER) because of their protected electronic states
and exceptional carrier mobility. Among them, the topological metal
Pt3Te4 (mitrofanovite) exhibits low Tafel slopes
in the nanocrystals. Realizing this potential in scalable catalyst
systems requires nanoscale texturing coupled with precise control
of the surface chemistry under operating conditions. Herein, we demonstrate
that hydrogen peroxide (H2O2)-assisted liquid-phase
exfoliation (LPE) of bulk Pt3Te4 yields nanoporous
nanosheets that retain their metallic character and are chemically
preconditioned to develop a bias-controlled PtO2 skin that
governs the catalytic activity. Crucially, spectromicroscopy resolves
termination-selective oxidation: PtO2 forms exclusively
on PtTe2-like terminations, whereas Pt2Te2 terminations remain metallic. Operando ambient-pressure X-ray
photoelectron spectroscopy (AP-XPS) in an electrochemical cell revealed
the bias-dependent emergence of surface oxide phases in H2O2-treated nanosheets. The joint effect of the higher
accessible site density imparted by nanoporosity and the emergence
of a bias-controlled PtO2/PtTe2-terminated Pt3Te4 surface junction rationalizes the improved
catalytic activity: the overpotential at 10 mA cm–2 decreases by ∼30% (from 113.1 to 78.7 mV), while the exchange
current density more than triples (from 0.106 to 0.347 mA cm–2), all with an unchanged Tafel slope (∼53 mV dec–1) and sustained stability over 50 h in acid. By combining a single
scalable top-down step with operando proof that the catalytically
active oxide is switched on by bias rather than being a static passivation
layer, this study establishes a precise interface-engineering principle
for Pt3Te4 nanosheets and a practical path to
efficient, scalable HER catalysts based on nanosheets of topological
metals.