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Immobilized Cobalt Bis(benzenedithiolate) Complexes: Exceptionally Active Heterogeneous Electrocatalysts for Dihydrogen Production from Mildly Acidic Aqueous Solutions
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acs.inorgchem.7b01589 Shawn C. Eady 1 , Molly M. MacInnes 1 , Nicolai Lehnert 1
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acs.inorgchem.7b01589 Shawn C. Eady 1 , Molly M. MacInnes 1 , Nicolai Lehnert 1
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A series of cobalt bis(benzenedithiolate) complexes with varying benzenedithiolate (general abbreviation: bdt2–) ring substitutions (S2C6X42–) were prepared and adsorbed on inexpensive electrodes composed of (a) reduced graphene oxide (RGO) electrodeposited on fluorine-doped tin oxide (FTO) and (b) highly ordered pyrolytic graphite (HOPG). The catalyst-adsorbed electrodes are characterized by X-ray photoelectron spectroscopy. Catalyst loading across the ligand series improved notably with increasing halide substitution [from 2.7 × 10–11 mol cm–2 for TBA[Co(S2C6H4)2] (1) to 6.22 × 10–10 mol cm–2 for TBA[Co(S2C6Cl4)2] (3)] and increasing ring size of the benzenedithiolate ligand [up to 3.10 × 10–9 mol cm–2 for TBA[Co(S2C10H6)2] (6)]. Electrocatalytic analysis of the complexes immobilized on HOPG elicits a reductive current response indicative of dihydrogen generation in the presence of mildly acidic aqueous solutions (pH 2–4) of trifluoroacetic acid, with overpotentials of around 0.5 V versus SHE (measured vs platinum). Rate constant (kobs) estimates resulting from cyclic voltammetry analysis range from 24 to 230 s–1 with the maximum kobs for TBA[Co(S2C6H2Cl2)2] (2) at an overpotential of 0.59 V versus platinum. Controlled-potential electrolysis studies performed in 0.5 M H2SO4 at −0.5 V versus SHE show impressive initial rate constants of over 500 s–1 under bulk electrolysis conditions; however, steady catalyst deactivation over an 8 h period is observed, with turnover numbers reaching 9.1 × 106. Electrolysis studies reveal that halide substitution is a central factor in improving the turnover stability, whereas the ring size is less of a factor in optimizing the long-term stability of the heterogeneous catalyst manifolds. Catalyst deactivation is likely caused by catalyst desorption from the electrode surfaces.
中文翻译：
固定化的双（二硫代苯甲酸钴）配合物：从弱酸性水溶液中生产二氢的异常活性多相电催化剂
制备了一系列具有不同苯二硫代酸酯（一般缩写：bdt 2–）环取代（S 2 C 6 X 4 2–）的钴双（苯二硫代）钴配合物，并将其吸附在由（a）氧化石墨烯（RGO）组成的廉价电极上电沉积在掺氟氧化锡（FTO）和（b）高度有序的热解石墨（HOPG）上。催化剂吸附的电极通过X射线光电子能谱表征。随着卤化物取代的增加，TBA [Co（S 2 C 6 H 4）2从2.7×10 –11 mol cm –2]显着提高了整个配体系列的催化剂负载量（1）到TBA [Co（S 2 C 6 Cl 4）2 ]（3）]增加到6.22×10 –10 mol cm -2，并增加苯二硫代盐配体的环大小[最高达3.10×10 –9 mol cm –2用于TBA [Co（S 2 C 10 H 6）2 ]（6）]。对固定在HOPG上的配合物进行电催化分析会引起还原电流响应，表明存在三氟乙酸的弱酸性水溶液（pH 2-4）时产生二氢，相对于SHE，过电势约为0.5 V（相对于铂，测得）。循环伏安分析得出的速率常数（k obs）估计范围为24到230 s –1，TBA [Co（S 2 C 6 H 2 Cl 2）2 ]（2）的最大k obs在0.59 V的超电势下与铂金相比。在0.5 MH 2 SO中进行的控制电位电解研究与SHE相比，在-0.5 V时的4表现出令人印象深刻的初始速率常数，在本体电解条件下超过500 s –1；然而，在8小时内观察到催化剂稳定失活，周转数达到9.1×10 6。电解研究表明，卤化物取代是提高周转稳定性的关键因素，而环的大小则不是优化非均相催化剂歧管长期稳定性的因素。催化剂失活很可能是由于催化剂从电极表面解吸引起的。
更新日期：2017-09-21
中文翻译：
固定化的双（二硫代苯甲酸钴）配合物：从弱酸性水溶液中生产二氢的异常活性多相电催化剂
制备了一系列具有不同苯二硫代酸酯（一般缩写：bdt 2–）环取代（S 2 C 6 X 4 2–）的钴双（苯二硫代）钴配合物，并将其吸附在由（a）氧化石墨烯（RGO）组成的廉价电极上电沉积在掺氟氧化锡（FTO）和（b）高度有序的热解石墨（HOPG）上。催化剂吸附的电极通过X射线光电子能谱表征。随着卤化物取代的增加，TBA [Co（S 2 C 6 H 4）2从2.7×10 –11 mol cm –2]显着提高了整个配体系列的催化剂负载量（1）到TBA [Co（S 2 C 6 Cl 4）2 ]（3）]增加到6.22×10 –10 mol cm -2，并增加苯二硫代盐配体的环大小[最高达3.10×10 –9 mol cm –2用于TBA [Co（S 2 C 10 H 6）2 ]（6）]。对固定在HOPG上的配合物进行电催化分析会引起还原电流响应，表明存在三氟乙酸的弱酸性水溶液（pH 2-4）时产生二氢，相对于SHE，过电势约为0.5 V（相对于铂，测得）。循环伏安分析得出的速率常数（k obs）估计范围为24到230 s –1，TBA [Co（S 2 C 6 H 2 Cl 2）2 ]（2）的最大k obs在0.59 V的超电势下与铂金相比。在0.5 MH 2 SO中进行的控制电位电解研究与SHE相比，在-0.5 V时的4表现出令人印象深刻的初始速率常数，在本体电解条件下超过500 s –1；然而，在8小时内观察到催化剂稳定失活，周转数达到9.1×10 6。电解研究表明，卤化物取代是提高周转稳定性的关键因素，而环的大小则不是优化非均相催化剂歧管长期稳定性的因素。催化剂失活很可能是由于催化剂从电极表面解吸引起的。
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