Efficient bipolar membranes with Ti3C2Tx nanosheets as advanced catalysts in the interfacial layers for water splitting

The main key component in bipolar membranes (BPMs) is the interfacial layer (IL), which is responsible for the water splitting. In this work, a most studied MXene Ti3C2Tx and a modified Ti3C2Tx (PANI-Ti3C2Tx) were investigated as the catalysts in ILs of BPMs. BPMs with Ti3C2Tx/PANI-Ti3C2Tx were prepared through the layer-by-layer casting/spraying method. The resulting BPMs were assessed through morphologies, thermal stability, alkali resistance performance, current-voltage (I-V) curves and water splitting performance in the bipolar membrane electrodialysis (BMED). Results show that the as-prepared BPMs exhibited excellent adhesion between layers, good thermal stability and alkali resistance performance. I-V curves showed that the voltage of the BPM with the PANI-Ti3C2Tx addition content of 0.5% (BPM-PANI-Ti3C2Tx-0.5%, ∼7.0 V) at the current density of 80 mA·cm−2 was only half of that of the blank sample BPM-0 without any catalysts (∼14.1 V). After the BMED operation, the final OH- concentration increment in the base chamber (∆COH) and the energy consumption of the BPM-Ti3C2Tx-1.0% membrane (0.089 mol·L−1, 0.58 kWh·mol−1) were ∼7% higher and ∼29% lower than those of BPM-0 (0.083 mol·L−1, 0.82 kWh·mol−1), respectively; BPM-Ti3C2Tx-1.0% (0.089 mol·L−1, 95%) showed a higher final ∆COH and current efficiency than the commercial membrane BP-1 (0.087 mol·L−1, 93%), but a higher energy consumption (0.58 kWh·mol−1) than BP-1 (0.33 kWh·mol−1). This study suggests that MXenes have the advanced catalytic effect on water splitting occurs in ILs of BPMs.