In order to reduce the global warming and related impact of fossil fuels, transition towards sustainable alternatives based on renewable energy becomes increasingly critical. Green hydrogen (H?) fuel has emerged as a game-changing renewable and clean-burning energy source, which generates no direct carbon emissions and only water as a by-product when used in fuel cells. Recognising the critical role of green H2 in sustainable energy, the Government of India launched the National Green Hydrogen Mission to drive large-scale production, promote research and innovation, and position the country as a global leader in H2 economy.

Among the environmentally benign methods of H2 production, overall water splitting stands out as an e?ective and scalable technique that relies on a catalytic strategy since the reaction is energetically uphill. Piezocatalysis has emerged as a promising catalytic technology which harvests mechanical perturbations with a piezoelectric material to generate charge carriers that are utilised to catalyse water splitting.

In recent groundbreaking research work, Professor Tapas K Maji from Chemistry and Physics of Materials Unit at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Bengaluru (an autonomous institution under the Department of Science & Technology, Govt. of India) and his research team have developed a metal-free donor-acceptor based covalent-organic framework (COF) for piezocatalytic water splitting. This study published in Advanced Functional Materials demonstrates a Covalent organic framework (COF) built from imide linkages between organic donor molecule tris(4-aminophenyl)amine (TAPA) and acceptor molecule pyromellitic dianhydride (PDA) acceptor exhibiting unique ferrielectric (FiE) ordering, which showed efficient piezocatalytic activity for water splitting to produce H2.

This discovery breaks the traditional notion of solely employing heavy or transition metal-based ferroelectric (FE) materials as piezocatalysts for catalysing water splitting reaction. Conventional FE materials have limited charges confined at the surface only which usually lead to quick saturation of their piezocatalytic activity. In contrast, FiE ordering in a COF provides a multifold enhanced number of charges at the pore surfaces owing to the large local electric fields. The sponge-like porous structure of a COF allows the diffusion of water molecules to efficiently access and utilize these charge carriers for catalysis, giving ultra-high H2 production yields and outperforming all oxide-based inorganic piezocatalysts.

News source: PIB