Zr掺杂CaMnO_(3)钙钛矿固溶体太阳能高温热化学储热性能研究

Investigation of Zr-doped CaMnO_(3) perovskite solid solution for high-temperature solar thermochemical energy storage

CaMnO_(3)钙钛矿氧化物廉价易得,能够在较大的温度和氧分压(p(O_(2)))范围内通过氧化还原反应实现热能的储存和释放,是具有应用潜力的聚光太阳能热化学储热材料.但是,由于CaMnO_(3)在高温还原过程中易发生部分分解,导致材料无法完全再氧化,严重限制了其热化学储热性能.本文提出Zr掺杂CaMnO_(3)的新型热化学储热材料,并对其物相结构、氧化还原容量、储热性能以及光谱吸收特性等开展实验和理论计算研究.结果表明:掺杂10%Zr元素的CaZr_(0.1)Mn_(0.9)O_(3)钙钛矿固溶体可在实现完全可逆氧化还原循环的同时,有效抑制材料还原过程中的分解现象.但随着Zr掺杂比例的进一步增加,产生的杂相将显著降低材料的氧化还原性能.采用van’t Hoff方法计算出CaZr_(0.1)Mn_(0.9)O_(3)在1000℃,p(O_(2))=10^(−5) atm条件下的储热密度为390.6±32.8 kJ/kg,且Zr的有效掺杂可提高CaMnO_(3)在近红外波段的太阳能光谱吸收率.通过密度泛函理论计算可知,Zr的有效掺杂提高了ABO_(3)氧化物中B–O化学键的强度,从而强化了其结构稳定性并提升了储热密度,为钙钛矿热化学储热材料的开发提供了指导和依据.

CaMnO_(3) perovskite oxide,composed of earth-abundant and cost-effective elements,could store and release heat by the redox reactions over a wide range of temperatures and partial pressures of oxygen(p(O_(2))).CaMnO_(3) perovskite oxide has been regarded as a promising candidate for thermochemical heat storage in concentrated solar power plants.However,CaMnO_(3) perovskite oxide is partially decomposed during the high-temperature reduction process,resulting in the incomplete reoxidation of the material,which severely limits its thermochemical energy storage performance.Herein,Zr-doped CaMnO_(3) has been proposed as a novel thermochemical energy storage material.Moreover,its phase structure,redox capability,energy storage performance,and solar spectral absorption properties have been thoroughly investigated through experimental and theoretical calculations.The results demonstrated that the CaZr_(0.1)Mn_(0.9)O_(3) perovskite solid solution could achieve a fully reversible redox cycle while effectively inhibiting decomposition during reduction.However,with the further increase in the Zr doping ratio,the produced side phases would significantly reduce the redox performance of the material.The thermochemical energy storage density of CaZr_(0.1)Mn_(0.9)O_(3) could reach 390.6±32.8 kJ/kg at 1000℃ and p(O_(2))=10^(−5) atm,and the effective doping of Zr could enhance the spectral absorption of CaMnO_(3) in the near-infrared region.According to the calculation of density functional theory,the effective doping of Zr could enhance the B-O chemical bond strength of ABO_(3) oxides,thus strengthening the structural stability and improving the thermochemical energy storage density.This study provides guidance for the development of perovskites for thermochemical energy storage.