The rapid development of photovoltaic technology provides more possibilities for the efficient application of solar energy in buildings. This research proposed a phase change material (PCM) heat storage wall system with a “four-layer” structure. A performance test platform using low voltage DC was built to study the mechanism of electric thermal conversion of the graphene electrothermal film and the heat transfer characteristics of the “four-layer” structure. As shown in the experimental results, under the voltages of 24 V, 32 V and 42 V, (1) with the increase in voltage, the temperature of the electrothermal film increases, while its electrothermal conversion efficiency decreases from 85% to 75%; (2) during the heat storage process, because of its latent heat storage characteristics, the temperature of the PCM wallboard is 3~5 °C lower than that of the cement wallboard, but the effective heat storage increases by 59~65%; (3) during the heat release process, the effective heat release of the PCM wallboard increases by 41–78%, and the maximum heat storage and release efficiency is 98%; and (4) at 32 V, the PCM can completely change phase. The theoretical calorific value of the electrothermal film is equivalent to the hourly power generation of 1.45 m2 of photovoltaic modules. The results provide basic data for the integration of photovoltaic and phase change technology and their efficient application in buildings.

Preventive environmental investment can enhance corporate environmental pollution management at the source and facilitate green transformation development. As a form of government of green investment behavior, urban greening construction exhibits a “demonstration effect” and “innovation effect” on corporate preventive environmental investment. To investigate this, the present study utilizes Chinese listed company and city-level data from 2011 to 2020 to analyze the influence, mechanism, and heterogeneity of urban greening construction on corporate environmental preventive investment. The findings indicate that urban green construction significantly encourages corporate preventive environmental investments by increasing enterprises’ willingness to participate in environmental regulation and advancing their green technology innovation. Furthermore, the environmental investment impact of urban greening construction exhibits considerable regional and corporate heterogeneity. Specifically, this effect is more pronounced in areas with lower marketability degrees and environmental regulation levels. It plays a more substantial role for state-owned enterprises and enterprises with lower agency costs.

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