An efficient hydrogen evolution catalyst composed of palladium phosphorous sulphide (PdP∼0.33S∼1.67) and twin nanocrystal Zn0.5Cd0.5S solid solution with both homo- and hetero-junctions
An efficient hydrogen evolution catalyst composed of palladium phosphorous sulphide (PdP∼0.33S∼1.67) and twin nanocrystal Zn0.5Cd0.5S solid solution with both homo- and hetero-junctions
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DOI：
10.1039/c6ee02414a
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发表时间：
2017-01
影响因子：
32.5
通讯作者：
Jingang Song;Haitao Zhao;R. Sun;Xiyou Li;Dejun Sun
中科院分区：
文献类型：
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作者：
Jingang Song;Haitao Zhao;R. Sun;Xiyou Li;Dejun Sun
−-xS固溶体是一种优良的可见光响应型催化剂，可在牺牲试剂存在下从水中析氢。由于闪锌矿(ZB)和纤锌矿(WZ)之间的同质结的存在，改善了光子产生的电子-空穴对的分离，特别是具有孪晶结构的Zn0.5Cd0.5S是迄今为止报道的最好的原始硫化物催化剂。然而，孪晶Zn0.5Cd0.5S固溶体催化活性的进一步提高尚未见报道。在本工作中，首次使用PdP∼0.33S∼1.67作为助催化剂，发现在酸性或碱性牺牲剂的存在下，孪晶纳米晶锌镉0.5S固溶体的光催化产氢速率和效率显著提高。在0.75M抗坏血酸(pH=2.39)和0.7M Na_2S/0.5M Na_2SO_3(pH=13.86)水溶液中，在可见光(420 Nm)照射下(λ>；420 nm)，样品的产氢速率分别为372.12μmolh−1 mg−1和246.04μmolh−1 mg−1，分别是原始孪晶Zn0.5Cd0.5S固溶体的67和5.8倍。此外，在酸性牺牲试剂存在下，硫化物光催化剂的产氢速率为372.12μ−1 mg−1，是迄今报道的最高值。用扫描电子显微镜、透射电子显微镜和高分辨透射电子显微镜对杂化催化剂的形貌进行了研究，结果表明，杂化催化剂中沉积的∼-0.33S-∼-1.67和∼-0.33S-∼-1.67之间存在异质结，而ZB-WZ相则为同质结。同质结和异质结在分离产生的电子-空穴对上的协同作用是杂化催化剂催化活性显著提高的原因。这一结果表明，将同质结和异质结结合在一个催化剂中是提高硫化物催化剂水析氢催化活性的一种有前途的策略。
ZnxCd1−xS solid solutions have been successfully demonstrated as excellent visible light responsive catalysts for hydrogen evolution from water in the presence of sacrificial reagents. Especially Zn0.5Cd0.5S with a twin crystal structure is the best pristine sulphide catalyst ever reported so far due to the presence of the homo-junctions between the zinc blende (ZB) and wurtzite (WZ) segments, which improved the separation of the photon generated electron–hole pairs. However, a further improvement in the catalytic activities of the twin crystal Zn0.5Cd0.5S solid solution has never been reported. In the present work, palladium phosphorous sulphide (PdP∼0.33S∼1.67) was used for the first time as a co-catalyst and found that the photocatalytic H2 production rate and efficiency of the twin nanocrystal Zn0.5Cd0.5S solid solution in the presence of acidic or alkaline sacrificial reagents were significantly enhanced. The H2 production rates of Zn0.5Cd0.5S/PdP∼0.33S∼1.67 under visible light illumination (λ > 420 nm) in 0.75 M ascorbic acid (pH = 2.39) and 0.7 M Na2S/0.5 M Na2SO3 (pH = 13.86) aqueous solutions are measured to be 372.12 μmol h−1 mg−1 and 246.04 μmol h−1 mg−1, respectively, which are 67 and 5.8 times higher than those of pristine twinned Zn0.5Cd0.5S solid solution. Moreover, the H2 production rate of 372.12 μmol h−1 mg−1 is the highest value ever reported so far for sulphide photocatalysts in the presence of acidic sacrificial reagents. The examination on the morphology of the Zn0.5Cd0.5S/PdP∼0.33S∼1.67 hybrid catalyst using SEM, TEM and HRTEM techniques revealed the presence of hetero-junctions between the deposited PdP∼0.33S∼1.67 and Zn0.5Cd0.5S phases, as well as homo-junctions between the ZB and WZ phases in this hybrid catalyst. The synergistic effects of homo- and hetero-junctions on the separation of the generated electron–hole pairs are responsible for the significantly promoted catalytic activities of the hybrid catalyst. This result suggests that combination of both homo- and hetero-junctions in one catalyst is a promising strategy for improving the catalytic activities of sulphide catalysts for hydrogen evolution from water.