Reversible solid oxide fuel cells (RSOCs) possess both fuel cell and electrolysis cell operating modes, with their electrolysis mode capable of H₂O-CO₂ co-electrolysis, serving as a novel carbon conversion technology. However, research on their application in distributed energy systems remains insufficient, and their potential for active carbon reduction has yet to be fully explored. This research proposes an integrated energy system coupling RSOCs with solar energy, establishes a system simulation model that includes combined cooling, heating, and power as well as active carbon emission reduction, and investigates the system’s operational characteristics across different seasons, fuel utilization rates, gas sources, and price fluctuations. Additionally, a comprehensive evaluation index considering energy efficiency, environmental benefits, economic performance, and sustainability is proposed. Taking the energy supply of a 2000 m² office building as an example, the maximum daily carbon emission reduction can reach 53 kg in summer when solar radiation is abundant. Furthermore, parametric studies indicate that fuel utilization rates and methane proportions are positively correlated with energy efficiency and exergy efficiency, while the system’s economic performance is most sensitive to electricity prices. The active carbon reduction energy system proposed in this study differs from passive reduction systems by achieving on-site active carbon emission absorption and can flexibly couple with traditional energy systems to meet the low-carbon emission requirements.

Proton exchange membrane water electrolyzer decomposes water into oxygen and hydrogen using electrical energy as the driving force. During the water electrolysis process, the anode catalyst layer is a key factor influencing the performance of the electrolyzer. Based on the initial structural parameters of the proton exchange membrane water electrolyzer, this study establishes a one-dimensional electrolysis model to investigate the effect of ionomers in the anode catalyst layer on the operational performance of electrolyzer. Six ionomers with different equivalent weights, including both long-chain and short-chain types, were compared. Proton conductivity of ionomers was corrected based on their equivalent weights, and interfacial contact resistance at different ionomer contents was calculated using the constriction resistance theory. Since excessive ionomer in the catalyst layer can cover the active sites of catalyst, there exists an optimal ionomer content in the anode catalyst layer. When using different types of ionomers, the optimal ionomer content varies due to differences in water absorption, which is related to the porosity of the catalyst layer after ionomer water absorption and swelling. Based on this, a formula related to the optimal porosity is proposed in this paper. Furthermore, the performance of short-chain ionomer consistently outperforms that of long-chain ionomer both before and after water absorption and swelling, which demonstrates the advantages of short-chain ionomers. This study can provide references for the optimal design of catalyst layer in proton exchange membrane water electrolyzer.