Rational construction of high-efficiency non-noble metal electrocatalysts for methanol electrooxidation reaction (MOR) is critical for energy conversion and high-value chemical electrosynthesis but remains challenging. Herein, N-doped Ni2P/CeO2 with abundant oxygen vacancies (N-Ni2P/CeO2-TA) is synthesized by electrodeposition, tannic acid (TA) defect engineering and low-temperature phosphorization. TA etching induces rich oxygen vacancies, regulates the Ce3⁺/Ce4⁺ redox equilibrium, and strengthens interfacial electronic modulation at the heterogeneous interface. Benefiting from the synergistic coupling of heterogeneous interface, nitrogen doping and oxygen vacancies, N-Ni2P/CeO2-TA delivers outstanding MOR activity: 1.348 V vs. RHE at 10 mA cm⁻2, Tafel slope of 56.5 mV dec⁻1 and 96.2% apparent Faradaic efficiency toward formate confirmed via 1H NMR. It retains 81.5% initial activity after 60 h durability measurement. DFT unveils that oxygen vacancies elevate Ni d-band center, optimize intermediate adsorption and reduce the *CH3O to *CH2O rate-determining-step barrier from 0.79 eV to 0.64 eV, accelerating MOR kinetics and favoring the formate‑formation pathway.
Owing to its distinct advantages of competitive pricing, high carbon yield and strong controllability, coal tar pitch (CTP) presents itself as a highly suitable and valuable precursor for fabricating carbon anodes in sodium-ion batteries (SIBs). However, the inevitable graphitization of CTP during pyrolysis hinders the sodium storage capacity of its derived carbon within the voltage plateau region (<0.1 V). Here, a heterogeneous cross-linking approach is proposed to regulate the microstructure of CTP-based carbon using citric acid. Through low-temperature pre-oxidation, cross-linking reactions occur between the oxygen-containing groups of citric acid and CTP to generate C(O)-O bonds, creating a steric hindrance effect that disrupts the two-dimensional plane arrangement of the carbon structure. The resulting POAC-41 anode with enlarged interlayer spacing and a wealth of closed pores achieves an initial reversible capacity of 292.7 mAh g−1 with initial Coulombic efficiency (ICE) of 66.6% at 0.1 A g−1. The second-cycle plateau capacity reached up to 200.7 mAh g−1. A series of characterizations demonstrate that the exceptional plateau capacity of POAC-41 stems from Na+ intercalation into graphite-like layers and the filling of closed pores. This citric-acid cross-linking strategy provides a facile and scalable route to high-plateau-capacity hard carbon from low-cost CTP, advancing practical anodes for SIBs for grid-scale storage.
Coal combustion byproducts are increasingly examined as secondary sources of rare earth elements (REEs) and critical elements (CEs), but resource appraisal based only on total concentration can overstate practical recovery potential and overlook environmental liabilities. This study integrated geochemical enrichment, acid extractability, contamination, and ecological risk to evaluate feed coal, fly ash, bottom ash, and mixed coal combustion residue. Thirty-six composite samples were characterized for elemental composition and mineralogy using standard laboratory techniques. Recovery performance was assessed through standardized hydrochloric-acid leaching, target-element leaching efficiency, matrix dissolution, selectivity, standardized HCl dosage, and a recovery-potential score. Environmental performance was evaluated using contamination factors, the pollution load index, geoaccumulation index, and potential ecological risk index. Fly ash contained the highest mean ΣREY concentration (1205.44 ± 182.95 mg kg − 1), enrichment factor (3.65 ± 0.36), target-element leaching efficiency (66.45 ± 8.20%), and recovery-potential score (0.77 ± 0.06). Mixed combustion residues retained substantial resource value but also had the highest mean pollution load and ecological risk. CRITIC–TOPSIS weighting shifted the strongest priorities toward fly ash and selected bottom-ash samples while reducing the priority of the most environmentally burdened residues. The integrated framework distinguished high-value recoverable streams, pre-treatment-dependent targets, environmental-management priorities, and low-priority materials, providing a defensible basis for screening coal-derived materials before detailed process development.
