Bipolar Electrochemistry as a Simple Synthetic Route toward Nanoscale Transition of Mo2B5 and W2 B5 for Enhanced Hydrogen Evolution Reaction
The development of non-noble metal and earth-abundant-basedelectrocatalysts for electrochemical hydrogen production is of great significance forlarge scale application of water splitting technology. Particularly, molybdenum- andtungsten-based materials, such as MoS2,WS2, MoP, and WP, are widely studied fortheir promising performance in catalyzing the hydrogen evolution reaction (HER),especially in their nanostructured forms. Here, we investigate the HER activity ofnanostructured molybdenum and tungsten borides, which are highly understudied, andreport the use of bipolar electrochemistry (BP) to enhance their performances. BPtreatment induces the size reduction of commercial Mo2B5and W2B5from themicrometer range down to the nanometer range. The smaller Mo2B5and W2B5particles have greater exposure of active sites for HER catalysis and result in better HERperformance. To illustrate, we found that the electrocatalytic performance of BP-treatedW2B5is close to the best HER electrocatalyst, Pt/C. Electrochemical impedancespectroscopy measurements reveal lower charge transfer resistance (Rct) of the materials after bipolar electrochemical treatment,thereby suggesting another effect of the BP method in enhancing HER catalysis. Overall, we demonstrate bipolarelectrochemistry as a simple method to improve the catalytic activity of Mo2B5and W2B5.