Mg 2+ Ions as Interfacial Charge Bridges for Enhanced Photocatalytic Hydrogen Evolution in Poly(Heptazine Imide)

Year: 2026

Type: article

Abstract: ABSTRACT Optimizing charge transfer at the solid‐liquid interface remains a central challenge for photocatalytic hydrogen evolution, particularly in polymeric semiconductors with limited electron‐donating ability. Here, we demonstrate that Mg 2+ incorporated into poly(heptazine imide) (PHI) acts as a catalytic promoter by synergistically coupling semiconductor charge transport with Pt co‐catalysts, thereby overcoming kinetically limited interfacial electron transfer. Using H 2 evolution as a model reaction, Mg incorporation into Na‐PHI enhanced the hydrogen evolution rate by more than 2.5‐fold and introduced a linear dependence on Pt loading, an effect absent in pristine Na‐PHI. In situ XANES reveals reversible electronic modulation of Mg 2+ exclusively in the presence of Pt and water, confirming its direct participation in interfacial charge mediation. Complementary photophysical, (photo)electrochemical, and molecular dynamics simulations indicate that Mg 2+ polarizes water molecules through a dynamic Mg 2+ ‐OH δ– H δ+ ‐Pt interfacial motif, facilitating proton transfer toward Pt while stabilizing hydroxide species. Beyond the activity enhancement, Mg‐PHI exhibits improved structural stability by resisting framework protonation during recycling. Collectively, these findings establish Mg 2+ as a catalytic promoter and demonstrate that interfacial charge‐bridge effects can be rationally heterogenized, providing a general strategy for enhancing photocatalytic hydrogen evolution through targeted interface engineering.

Source: Small

DOI: 10.1002/smll.75403

Authors: Gabriel A. A. Diab, Vitor G. S. Pastana, Sara Stolfi, Rayse M. Ferreira, Izadora F. Reis, Marcos A. R. da Silva, Caio V. C. Ribeiro, Kathrin Küster, Piero Torelli, Paolo Ghigna, Viola Duppel, Maurizio Fagnoni, Sebastian Bette, Bruna R. Serino, Andre F. de Moura, Davide Ravelli, Bettina V. Lotsch, Ivo F. Teixeira

Institutions: Universidade Federal de São Carlos, Max Planck Institute for Solid State Research, University of Pavia, Istituto Officina dei Materiali

Language: English

Topic: Advanced Photocatalysis Techniques

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: hybrid

Estimated APC paid: $5,790

Funders: Dipartimenti di Eccellenza, European Commission, Deutsche Forschungsgemeinschaft, Fundação de Amparo à Pesquisa do Estado de São Paulo, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Max-Planck-Gesellschaft, Financiadora de Estudos e Projetos, HORIZON EUROPE Framework Programme, Air Force Office of Scientific Research

OpenAlex ID: W7204468073