Heavy metal contaminated spent adsorbents are of great environmental concern due to their hazardous effects and large-scale accumulation in the natural environment. Converting massive spent adsorbents into efficient electrocatalysts with a facile strategy can address the challenge of growing energy demand and achieving carbon neutral goal. Herein, we demonstrated a "spent adsorbents to heterostructured electrocatalysts" conversion strategy based on the "waste-to-wealth" principle. Via a facile boriding process, the metal ions laden biochar-based spent adsorbents (SA) have been totally transformed into magnetic metal borides/biochar heterostructures, which exhibit excellent activities towards oxygen evolution reaction. The optimized NiCuFeB/SA catalyst takes a low overpotential of 251 mV to drive a current density of 10 mA cm⁻², outperforming many Ni/Fe-based catalysts synthesized from commercial material resources. Comprehensive analyses suggest the high catalytic efficiency mainly attributes to the porous biochar confined well-dispersed nano-sized metallic borides, the in-situ evolved active metal (oxy)hydroxides, favourable charge-transfer kinetics, as well as the heterostructure and amorphous feature. This work offers a general strategy to efficiently reutilize the spent metal-bearing biochar-based adsorbents, which can be extended to advanced energy applications-oriented reutilization of other metal-contaminated solid wastes in an economically and environmental-benign manner.

重金属污染的废吸附剂由于其有害影响和在自然环境中的大规模积累而引起极大的环境问题。用简单的策略将大量用过的吸附剂转化为高效的电催化剂，可以应对不断增长的能源需求和实现碳中和目标的挑战。在此，我们展示了一种基于“变废为宝”原则的“用过的吸附剂到异质结构电催化剂”的转化策略。通过简单的硼化过程，负载金属离子的生物炭基废吸附剂 (SA) 已完全转化为磁性金属硼化物/生物炭异质结构，其对析氧反应表现出优异的活性。优化的 NiCuFeB/SA 催化剂需要 251 mV 的低过电位来驱动 10 mA cm 的电流密度^-2，优于许多由商业材料资源合成的 Ni/Fe 基催化剂。综合分析表明，高催化效率主要归因于多孔生物炭限制的分散良好的纳米级金属硼化物、原位演化的活性金属（羟基）氢氧化物、有利的电荷转移动力学以及异质结构和无定形特征。这项工作提供了一种有效再利用废含金属生物炭基吸附剂的一般策略，该策略可以扩展到以经济和环境友好的方式对其他金属污染固体废物进行先进的面向能源应用的再利用。