钴氮掺杂木质衍生碳制备及其电催化性能研究

Preparation and Electrocatalytic Performances of Cobalt-nitrogen Doped Wood-derived Carbon

关键词:  生物质  木质衍生碳  氧还原反应  氧析出反应

Key Words:biomass  wood-derived carbon  oxygen reduction reaction  oxygen evolution reaction

摘要:本研究采用简单的路易斯酸水热预处理和高温热解制备了具有Co-N活性中心的钴氮掺杂木质衍生碳基双功能催化剂（CoHNC），并对其结构与性能进行研究。结果表明，路易斯酸（CoCl₂）可以部分水解木材中的纤维素和半纤维素，在细胞壁上形成丰富的微介孔，所得碳材料比表面积高达1 008.02 m²/g；预处理过程同步引入金属原子，在热解过程中形成Co-N活性位点。CoHNC独特的分级孔结构有利于电解质/氧气等物质的高效扩散及高密度活性位点的暴露，而Co—N结构可以有效调节催化局部微环境，进而提高多相催化性能。CoHNC表现出优异的电催化性能，在0.1 mol/L KOH溶液中，其氧还原半波电位达0.869 V vs. RHE，在电流密度为10 mA/cm²时，氧析出过电位为274 mV，电位差ΔE仅为0.635 V，优于商用Pt/C和RuO₂。

Abstract:In this study， a cobalt-nitrogen doped wood-derived bifunctional catalyst （CoHNC） with Co-N active sites was prepared via a simple Lewis acid hydrothermal pretreatment and followed by a high-temperature pyrolysis. The physicochemical structures and electrochemical properties of CoHNC were investigated. The results showed that Lewis acids could partly hydrolyze the cellulose and hemicellulose in the wood， resulting in abundant nanopores， and a high specific surface area of 1 008.02 m²/g. Metal atoms coordinate with the oxygen-containing functional groups during hydrothermal pretreatment， which was then converted into Co-N active sites after pyrolysis. The hierarchical pore structure of CoHNC facilitated the efficient diffusion of electrolyte/oxygen and the exposure of high-density active sites. The Co—N structure could effectively regulate the microenvironment of the catalyst， and thus improve the catalytic performance. CoHNC presented excellent oxygen reduction reaction（ORR） and oxygen evolution reaction（OER） activities with a positive half-wave potential of 0.869 V vs. RHE in 0.1 mol/L KOH solution， a OER overpotential of 274 mV at a current density of 10 mA/cm² and a ∆E of only 0.635 V， which outperform those of commercial Pt/C and RuO₂.