The exposed surface facets play an important role in determining the catalytic performance of nanostructured materials. In this study, we report the synthesis of hematite nanoparticles with three varying morphologies with exposure of well-controlled {104}, {113} and {001} surfaces. The better shape control of hematite particles has provided a direct correlation between the surface facets and the photocatalytic performance. The catalytic photodegradation of MB using hematite nanoparticles reveals that the reaction follows the heterogeneous photo-Fenton process under visible light irradiation. The catalytic performance of hematite surface facets follows the order of {113} > {104} > {001}. Density functional theory (DFT) calculations were conducted to demonstrate the atomic surface structures and the corresponding charge distribution. The results indicate that the catalytic activity depends on surface atom arrangements as well as the number and the type of surface terminated hydroxyl groups bonding to underlying Fe atoms, where low valence states of Fe on {104} and {113} planes have the highest probability to be oxidized by H₂O₂ and the concurrently generated Fe^(3+x)+ sites are more electronegative to accept electrons from activated dye molecules. The findings are of fundamental importance to understand the surface-dependence of photocatalytic properties, thus shedding new light on the catalytic application of hematite particles.

The electrochemical conversion of nitrate to ammonia is a way to eliminate nitrate pollutant in water. Cu-Co synergistic effect was found to produce excellent performance in ammonia generation. However, few studies have focused on this effect in high-entropy oxides. Here, we report the spin-related Cu-Co synergistic effect on electrochemical nitrate-to-ammonia conversion using high-entropy oxide Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2O. In contrast, the Li-incorporated MgCoNiCuZnO exhibits inferior performance. By correlating the electronic structure, we found that the Co spin states are crucial for the Cu-Co synergistic effect for ammonia generation. The Cu-Co pair with a high spin Co in Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2O can facilitate ammonia generation, while a low spin Co in Li-incorporated MgCoNiCuZnO decreases the Cu-Co synergistic effect on ammonia generation. These findings offer important insights in employing the synergistic effect and spin states inside for selective catalysis. It also indicates the generality of the magnetic effect in ammonia synthesis between electrocatalysis and thermal catalysis.

Intensive research in electrochemical CO₂ reduction reaction has resulted in the discovery of numerous high-performance catalysts selective to multi-carbon products, with most of these catalysts still being purely transition metal based. Herein, we present high and stable multi-carbon products selectivity of up to 76.6% across a wide potential range of 1 V on histidine-functionalised Cu. In-situ Raman and density functional theory calculations revealed alternative reaction pathways that involve direct interactions between adsorbed histidine and CO₂ reduction intermediates at more cathodic potentials. Strikingly, we found that the yield of multi-carbon products is closely correlated to the surface charge on the catalyst surface, quantified by a pulsed voltammetry-based technique which proved reliable even at very cathodic potentials. We ascribe the surface charge to the population density of adsorbed species on the catalyst surface, which may be exploited as a powerful tool to explain CO₂ reduction activity and as a proxy for future catalyst discovery, including organic-inorganic hybrids.