The development of low-cost platinum-free electrocatalysts for the oxygen reduction reaction (ORR) is essential for the sustainable energy technologies. In this work, spinel-type LiMn₂O₄ was chemically modified via proton exchange to systematically investigate the effects of protonation on crystal structure, electronic configuration, and ORR performance. Experimental results reveal that proton exchange not only regulates the lattice parameters and Mn oxidation states, but also enhances surface hydrophilicity and oxygen adsorption capacity, leading to a significant improvement in ORR activity with at a half-wave potential of 0.81 V for pure Mn-based oxide. Physical characterizations and theoretical calculations reveal that protonation optimizes the surface electronic structure by mitigating the over-stabilization of oxygen intermediates on LiMn₂O₄, thus facilitating the rate-determining step *OH adsorption and improving reaction kinetics. This work establishes proton exchange as a versatile strategy for the construction of Mn-based oxide electrocatalysts containing alkali metals, offering valuable insights for the rational design of non-precious metal catalysts in energy conversion applications.

The increasing emission of carbon dioxide (CO₂) has intensified global efforts toward its conversion and utilization. Electrocatalytic CO₂ reduction reaction (CO₂RR) has emerged as a promising sustainable strategy to address interconnected energy and environmental challenges. Among the various products of CO₂ reduction, methanol has attracted significant research attention as both an essential chemical feedstock and a promising renewable energy carrier. This review comprehensively summarizes recent advances in the electrocatalytic conversion of CO₂ to methanol, with systematic discussions on fundamental reaction mechanisms and pathways, innovative reactor configurations, diverse catalysts, and auxiliary optimization strategies. Particular emphasis is placed on categorizing and evaluating various catalysts, including mono-/bimetallic catalysts, molecular catalysts, enzyme catalysts, and carbon-based materials, while exploring their structure-activity relationships and performance enhancement strategies for improving methanol selectivity. Furthermore, the techno-economic viability of current processes is analyzed, assessing the cost-effectiveness and commercial potential of electrocatalytic methanol production. Finally, based on current research progress and existing challenges, key research directions are outlined to advance the development of commercially feasible electrocatalytic CO₂-to-methanol systems, providing practical guidance for future investigations.

Thermally integrated Carnot battery (TI-CB) systems offer unique advantages for industrial waste heat recovery, but their performance under fluctuating, off-design conditions remains poorly understood. To address this gap, this study proposes a quasi-dynamic mathematical model with solution methodologies applicable to both design and off-design operating conditions. A dynamic evaluation framework is also developed to account for the temporal mismatch between energy storage and release processes. A multi-operating-condition set constructed via multivariable sampling is used to enable systematic analysis of key design parameters under both design and off-design conditions. The results reveal that heat source utilization parameters and heat pump temperature rise are dominant factors affecting TI-CB performance, while off-design analysis shows that ORC mass flow rate variations have a more significant impact on system performance than heat pump fluctuations. Due to irreversible heat losses, an increase in the heat source temperature difference leads to a decrease in round-trip efficiency (η_rt) from 62.6% to 45.8%, while η_orc and η_ex also exhibit downward trends. A higher temperature lift in the heat pump results a decrease in the mean COP from 7.6 to 4.8, whereas η_orc increases from 7.0% to 10.2%. Among working fluids evaluated, R1336mzz(Z) demonstrates superior performance but exhibits nonlinear behavior, while R1233zd(E) provides optimal stability across operating ranges, making it suitable for practical engineering applications.