Regulating the electronic structure of active sites through electronegativity difference offers a promising route to high-efficiency bifunctional electrocatalysis, yet systematic comparisons based on isostructural model catalysts remain limited. Herein, Cu2O nanocubes are used as a common precursor template to construct structurally comparable Cu2X (X = S, Se, and Te) nanocubes via a vapor-phase isomorphous substitution strategy for alkaline water splitting. Among the obtained catalysts, Cu2Se exhibits the best bifunctional activity, requiring overpotentials of only 56 mV for the hydrogen evolution reaction (HER) and 131 mV for the oxygen evolution reaction (OER) at 10 mA cm−2. When employed as both the cathode and anode, the Cu2Se||Cu2Se electrolyzer delivered 10 mA cm−2 at 1.52 V, with a Faradaic efficiency close to 100%, and retained 95.2% of its initial activity after 150 h of continuous operation. In a single-cell anion exchange membrane water electrolyzer, the Cu2Se-based device further achieved 500 mA cm−2 at 2.89 V and operated stably for 1000 h at 70 °C. Structural and electrochemical analyses indicate that chalcogen substitution preserves the nanocube framework while modulating the local electronic structure of Cu sites. The moderate electronegativity difference between Cu and Se is found to be particularly favorable for optimizing the electron density of Cu, increasing electrochemically accessible active sites, and accelerating interfacial charge transfer. This study establishes a structurally comparable Cu2X platform for elucidating electronegativity difference driven electronic regulation and offers a feasible strategy for designing efficient Cu-based bifunctional catalysts for alkaline water splitting.
This study presents the first cradle-to-gate life cycle assessment of compressed and heated geopolymer pavement blocks incorporating 100% hazardous industrial by-products (municipal solid waste incineration fly ash and red mud) as aluminosilicate precursors, benchmarked against mould-cast cement-based and geopolymer systems from the literature using the midpoint methodology across 18 impact categories. The compressed geopolymer formulations achieved global warming potential of 0.051–0.066 kg CO₂eq/kg block, representing reductions of 55–76% relative to cement-based comparators, with consistently superior performance across all 18 categories. Embodied energy (0.52–0.57 MJ/kg) and material cost (0.028–0.037 US$/kg) were the lowest among all systems evaluated. TOPSIS multi-criteria analysis ranked all three compressed formulations in the top three positions. Sensitivity analysis also confirmed that the environmental superiority is statistically robust across alkali activator dosage variation and transport distance scenarios. These findings establish pressurised and heated geopolymer technology as a systemically superior and cost-competitive pathway for hazardous waste valorisation in pavement block manufacturing.
