Electrolysis is the process of using electricity to split water into hydrogen and oxygen. Currently, precious metals tend to provide the catalytic materials needed for the process. These metals are scarce & expensive. But researchers in Australia have identified a new option, made of cheaper more readily available minerals, which also reacts more quickly.
Energy associated with ocean currents can be captured, just like wind currents can with wind turbines. Ocean turbines can be fixed to the seabed, or float nearer the surface with moorings attached to the seafloor. No one technology has yet emerged as a clear winner, but this Japanese turbine, which has been in development and testing for many years is clearly still in the race. After successful recent trials, the company is set to scale up to a 2 megawatt unit. https://www.sciencealert.com/japan-s-dropping-a-kaiju-sized-turbine-into-the-ocean-to-fish-for-limitless-energy
Steam turbines have to date been the most traditional way to covert heat into electricity. Steam turbines are able to convert between 35-60% of the heat into electricity. However, scientists have kept investigating alternative ways to turn heat into electricity. Thermophotovoltaic cells (TPV) were initially promising, but only ever achieved efficiency rates of 20-32%. By increasing both the temperature of the heat emitter & the absorption properties of the TVC (visible, ultraviolet & infrared) engineers at MIT have achieved efficiency rates of 40%, with a clear idea of how to reach 50%.