Unveiling subsurface hydrogen inhibition for promoting electrochemical transfer semihydrogenation of alkynes with water  

揭示次表面氢抑制促进炔烃电催化半氢化性能

作　　者：Qi Hao Yongmeng Wu Cuibo Liu Yanmei Shi Bin Zhang 郝琦;吴永萌;刘翠波;史艳梅;张兵(天津大学理学院化学系,分子+研究院,天津300072;天津大学教育部合成生物前沿科学中心,天津市分子光电科学重点实验室,天津300072)

机构地区：[1]a Department of Chemistry,Institute of Molecular Plus,School of Science,Tianjin University,Tianjin 300072,China [2]Frontiers Science Center for Synthetic Biology,Key Laboratory of Systems Bioengineering(Ministry of Education),Tianjin University,Tianjin 300072,China

出　　处：《Chinese Journal of Catalysis》2022年第12期3095-3100,共6页催化学报（英文）

基　　金：国家自然科学基金(21871206,22001192).

摘　　要：Highly selective electrocatalytic semihydrogenation of alkynes to alkenes with water as the hydrogen source over palladium-based electrocatalysts is significant but remains a great challenge because of the excessive hydrogenation capacity of palladium.Here,we propose that an ideal palladium catalyst should possess weak alkene adsorption and inhibit subsurface hydrogen formation to stimulate the high selectivity of alkyne semihydrogenation.Therefore,sulfur-modified Pd nanowires(Pd-S NWs)are designedly prepared by a solid-solution interface sulfuration method with KSCN as the sulfur source.The introduction of S weakens the alkene adsorption and prevents the diffusion of active hydrogen(H^(*))into the Pd lattice to form unfavorable subsurface H^(*).As a result,electrocatalytic alkyne semihydrogenation is achieved over a Pd-S NWs cathode with wide substrate scopes,potential-independent up to 99%alkene selectivity,good fragile groups compatibility,and easily synthesized deuterated alkenes.An adsorbed hydrogen addition mechanism of this semihydrogenation reaction is proposed.Importantly,an easy modification of commercial Pd/C by in situ addition of SCN–enabling the gram-scale synthesis of an alkene with 99%selectivity and 95%conversion highlights the promising potential of our method.烯烃是生产高附加值精细化工产品和工业聚合级乙烯的基本原料,炔烃选择性半氢化反应是烯烃合成的重要途径.近年来,研究者致力于发展经济、绿色的炔烃半氢化方法.最近,以水为氢源的炔烃电催化转移半氢化由于避免了氢气和有机氢化试剂的使用而引起了广泛关注.该方法中水电解在催化剂表面产生的表面吸附氢(H^(*)_(ads))是关键的氢物种,通过催化剂改性或改变施加电位可以控制H^(*)_(ads)的数量,从而调控反应的效率和选择性.然而,催化剂的次表面吸收氢(H^(*)_(abs))常被忽略,且热催化中已经证实H^(*)_(abs)具有比H^(*)_(ads)更强的氢化能力,是导致烯烃过度氢化而降低炔烃半氢化选择性的主要原因.但是,H^(*)_(abs)在电催化炔烃半氢化中的作用尚不清楚.因此,探索催化剂中H^(*)_(abs)对电催化炔烃半氢化的影响具有重要意义.钯(Pd)基材料具有良好的C≡C键活化能力和储氢能力,是均相和非均相炔烃半氢化反应的首选催化剂.但单质Pd往往难以达到理想的选择性要求,通常需要对其改性修饰.本课题组曾以Pd-P为阴极成功实现了以水为氢源的炔烃电催化转移半氢化(Angew.Chem.Int.Ed.,2020,59,21170-21175).然而,P的引入难以有效地抑制烯烃的过氢化,烯烃的选择性仍然高度依赖于施加电位.硫(S)是一种常用的炔烃半氢化催化剂改性剂,S的引入可以减弱金属对烯烃的吸附从而提高烯烃的选择性.但是S对金属催化剂在电催化半氢化过程中H^(*)_(abs)的形成的影响以及H^(*)_(abs)对烯烃选择性的作用仍有待深入研究.此外,钯硫化物(Pd-S)的合成通常是以具有毒性和腐蚀性的H_(2)S、硫醇等为S源在高温条件下进行的,容易引发环境和安全问题.而且,该方法难以控制产物中S含量,过量的S会占据Pd活性位点,导致催化活性显著下降.基于此,本文发展了一种室温下简单可控的Pd-S电催化剂合成方法,并揭�

关 键 词：ELECTROCATALYSIS Alkyne semihydrogenation Selectivity Hydrogen adsorption Interface sulfuration 

分 类 号：TQ221.2[化学工程—有机化工] TQ426