Performance and Structural Correlations of Low-Grade-Coal-Derived Carbon Additives for Coal-Water Slurry Electrolysis

This work systematically investigates the physicochemical, structural, morphological, and spectroscopic characteristics of raw, deashed, and electrolyzed coal samples to elucidate the role of inherent mineral phases in governing the electrolysis performance of coal-water slurry (CWS), with implications for hydrogen evolution and sustainable coal valorization. Morphological analyses reveal that acid washing and deashing induce pronounced structural reorganization of the coal matrix, significantly altering its electrochemical behavior. Electrochemical measurements demonstrate that mineral-rich raw coals exhibit higher current densities at lower overpotentials for both anodic and cathodic reactions, indicating that intrinsic mineral phases play a beneficial role in promoting the electrocatalytic activity during CWS electrolysis. Complementary Fourier transform infrared spectroscopy, Raman spectroscopy, and solid-state 13C NMR analyses conducted before and after electrolysis reveal pronounced oxidative structural evolution, including the depletion of aliphatic functionalities, enrichment of C═O, C–O, and C═C groups, and increased aromatic condensation, leading to the formation of a more partially ordered carbon framework. These findings reveal a strong interplay among mineral composition, electrochemical activity, and electrolysis-induced structural transformation of coal. Importantly, this study provides new mechanistic insights into the catalytic role of inherent mineral phases in CWS electrolysis and highlights abundant low-grade, mineral-rich coals as promising and sustainable feedstocks for efficient hydrogen generation and advanced coal valorization strategies.