This thesis focuses on the rational design, synthesis, and performance optimization of semimetal-based atomically dispersed catalysts—particularly selenium (Se) and tellurium (Te)—for use in energy-related electrochemical reactions. Unlike widely studied transition metals, this work centers on the relatively unexplored territory of semimetals, leveraging their unique chemical properties and coordination environments. By tailoring single-atom or cluster-scale catalytic sites, we exploit their high atomic dispersion and unique local structures to achieve superior electrochemical catalytic activity.

Despite their exceptional capabilities, atomically dispersed catalysts often undergo structural evolution—changes in morphology, elemental distribution, and coordination environments—during catalysis reaction. To address this challenge, we employed in situ X-ray absorption fine structure (XAFS) techniques with complementary characterization methods, we systematically examined the synthesis of these catalysts, their local atomic coordination environments, electronic structures, and semimetal-support interactions. Additionally, we explored their evolution under operational conditions, identifying key deactivation pathways. Consequently, we developed a “synthesis–structure–performance” framework for rational catalyst design. Key advancements include:

1. Revealing the Evolution of Active Sites in Atomically Dispersed Se Catalysts for Electrocatalytic Hydrazine Oxidation

We developed a structurally uniform atomically dispersed Se catalyst (Se@C-1000) with remarkable electrocatalytic performance in hydrazine oxidation (HzOR). In situ XAFS demonstrated the initial “Se–C₄” structure readily adsorbs hydroxide ions in the electrolyte solution to form the active species “HO–SeC₄”, reducing the reaction energy barrier and enabling highly efficient HzOR.

2. Coordination Engineering to Modulate the Local Covalency of Atomically Dispersed Te Sites for Enhanced Durability in Electrochemical CO₂ Reduction

Using a rapid spark plasma sintering (SPS) carbonization approach, we fabricated an atomically dispersed Te catalyst (Te@N3) featuring strong bond covalency and broken symmetry. At an applied potential of −0.8 V vs. RHE, Te@N3 achieved a CO selectivity of 98.6% and a Faradaic efficiency above 96% for over 400 hours at 80 mA cm⁻². Theoretical calculations revealed that enhanced covalency in Te–N bonds mitigates structural degradation under high electrolysis rates, preserving the active site’s integrity.

3. Time-Resolved In Situ XAFS Reveals the Chemical Evolution of Te Cluster Catalysts for Durable Hydrogen Evolution

We synthesized Te cluster catalysts (Te-ACs@NC) supported on porous carbon, achieving outstanding hydrogen evolution reaction (HER) performance. Time-resolved in situ XAFS revealed repetitive deactivation–regeneration cycles triggered by a surface phase transition. Even after 10 cycles (480 hours), Te-ACs@NC retained 85% of its initial activity.

4. Anchoring Atomically Dispersed Se Sites in MXene Vacancies for Efficient Electrocatalytic Oxygen Reduction

Leveraging defect-rich structures and large surface areas of MXene, we anchored Se atoms onto Mo₂C-type MXene (Se@Mo₂CT_X) through a self-reduction process. The Se atoms were confined in Mo vacancies as isolated atoms in Se@Mo₂CT_X and exhibited exceptional activity and stability in the oxygen reduction reaction (ORR).