金属掺杂TiO2纳米粒子电化学催化合成氨

Metal⁃doped TiO2 nanoparticles as catalysts for electrochemical ammonia synthesis

通过溶胶⁃凝胶法制备了三种过渡金属掺杂的TiO2纳米颗粒(TiO2⁃M,M=Cu,Mn,Pd),XRD和XPS等结构表征结果表明掺杂的金属以-O-M-O-的不饱和配位形式存在于TiO2纳米颗粒表面.在N2饱和的0.01 mol·L^-1 K2SO4溶液中,-0.55 V(vs.Ag/AgCl)阴极电位下分别测试了三种TiO2⁃M颗粒的电催化合成氨性能,其中TiO2⁃Pd催化合成氨速率(RNH3)达到1.54×10-11 mol·s^-1·cm^-2,但电流效率(FE)只有0.78%;而TiO2⁃Cu的RNH3为9.77×10-12 mol·s^-1·cm^-2,而FE达到15.33%.线性扫描伏安测试结果表明三种催化剂的析氢催化活性顺序为TiO2⁃Pd>TiO2⁃Mn>TiO2⁃Cu,且阴极电位负移导致电催化合成氨FE下降,意味着电催化合成氨的电流效率与催化剂自身的析氢催化活性密切相关.

TiO2 nanoparticles doped with metal elements(TiO2⁃M,M=Cu,Mn,Pd)were prepared via the sol⁃gel method.Characterizations demonstrated that these doped metals were embedded on the surface of TiO2 in unsaturated⁃coordination modes(-O-M-O-).The catalytic performance of these TiO2⁃M nanoparticles on electrochemical ammonia synthesis(EAS)was tested using N2 as feeding gas in a 0.01 mol·L^-1 K2SO4 solution at-0.55 V(vs.Ag/AgCl).The results showed that a RNH3 of 1.36×10-11 mol·s^-1·cm^-2 was achieved on TiO2⁃Pd,but the FE was only 0.78%,while a FE of 15.33%with a RNH3 of 9.77×10-2 mol·s^-1·cm^-2 was achieved on TiO2⁃Cu.The linear sweep voltammetry showed that the catalytic activity sequence of the three catalysts for hydrogen evolution reaction(HER)is TiO2⁃Pd>TiO2⁃Mn>TiO2⁃Cu,and the negative shift of cathode potential leads to the decrease of FE in EAS,which means that the current efficiency of a EAS catalyst is closely related to its catalytic activity for HER.